SMP HiFi 2 Development Board

This is a "community" guide for how to use the LX200 board based 3-core SMP HiFi-2 Development environment. If something doesn't work or isn't covered in this guide, please feel free to ask at the Linux/Xtensa Mailing List.

NEWS:

Some general notes on these instructions:

• They are a work in progress, though virtually complete. Just needs to have an a another engineer at Tensilica run through this procedure and make sure that we haven't missed anything.

• The following was tested on x86 machines running RedHat Fedora Core 5 and Fedora Core 9. Test done while using the Fedora 9 based kernel and the stable branch of the Xtensa kernel appear, so far, to be a bit better. Not seeing any compile errors while stressing the system with LTP, two compiles, two mplayers, hifitest, top, pstree, and top for the

first 18 hours; appears to be running perfect till then. No gcc commands or ssh sessions getting killed until almost a day of testing. Only the Unaligned memory access warning on gethostid01 that a staff engineer diagnosed as being a mistake in the gethostid01 LTP test program.

• NOTE for Internal Tensilica pre-release Testers:
  • Codecs available at /fac/vol6/audio/release/bin/l32r_LE5_pic.
  • LX200 bitstream available at /home/marc/XTAV200/test_mmuhifi_c3.3core.
  • Instructions to install and set up U-Boot available at http://wiki.linux-xtensa.org/index.php/Setting_up_U-Boot.
    • Checkout the snapshot_2+SMP branch of the U-Boot git repo for pre-built binaries.

Introduction

This document is addressed to someone who received an LX200 board setup by Tensilica for HiFi2 development.

This document goes over the steps needed to set up the LX200 board for HiFi2 development. To summarize:

• Setup the board. It likely comes with U-boot pre-installed, ready to boot a linux kernel.
• Install git.
• Download buildroot and linux kernel trees, pre-configured and built for HiFi-2 development.
• Setup a TFTP server to provide the linux kernel to U-Boot.
• Setup an NFS server to export a linux root file system.
• Setup the Linux kernel to boot from the root file system provided by the NFS server.
• Suggests a possible way to tailor the board for easy codec development just before booting.

Once the development board is up and running, this document:

• Shows how to add the Tensilica provided codec packages to the Mplayer packages used by Buildroot, including building and installing.
• Demonstrates two procedures for compiling, linking, and debugging codecs.
• Suggest how to add their code to buildroot and come up again with their same development environment.

All development is expected to be done on a Linux host. (One can in principle use Windows to develop target libraries. However, linking and subsequent steps need to be done in Linux.)

Downloading the Latest HiFi-2 Buildroot and Kernel Snapshots

The HiFi-2 development environment is maintained in a source code version control system named 'git'. The git tools are useful when working with this development environment, though they are not strictly necessary. This document generally assumes the use of git, which provides more opportunities for modifying this environment as needed (e.g. building more optional buildroot packages). But points out alternatives to allow getting up and running without having to set it up.

Installing git

To install git, download a recent tarball from the official site. For example, cd to a location with enough disk space, and do:

       $ wget http://www.kernel.org/pub/software/scm/git/git-1.6.5.tar.gz

Unpack the tarball, and make and install it. Here we show how to install it to your ~/bin directory:

       $ gunzip git-1.6.5.tar.gz
       $ tar xf git-1.6.5.tar
       $ cd git-1.6.5
       $ make
       $ make install

The git makefile can be instructed to install git to /usr/local/bin as root for system wide access:

       $ cp git-1.6.5.tar.gz /tmp
       $ su
       Password: 
       # cd /usr/local/src/
       # mkdir git
       # cd git
       # cp /tmp/git-1.6.5.tar.gz .
       # gunzip git-1.6.5.tar.gz
       # tar xf git-1.6.5.tar
       # cd git-1.6.5
       # make prefix=/usr/local
       # make install

See the 'INSTALL instruction at the top of the git src directory for details.

Using git provides easy access to the binaries used to bring up the codec development environment, and leaves in place the infrastructure to modify and build this environment should you wish to. Any changes to git-managed source trees are easily observed with the git tools.

Installing the Buildroot Snapshot

Note: The HiFi-2 snapshot is in the process of being made.

To install the buildroot environment (toolchain and root filesystem), cd to a location with a few GB of available disk space, and do:

   $ git clone git://git.linux-xtensa.org/git/buildroot/buildroot-xtensa-HiFi2-Snapshot.git
   $ cd buildroot-xtensa-HiFi2-Snapshot
   $ git branch --track snapshot_2+SMP origin/snapshot_2+SMP 
   $ git checkout snapshot_2+SMP 
                               

The last two lines checkout the latest branch (preconfigured for the 3-core HiFi2 on the LX200).

You can examine the tree (git repository) and its history visually using git gui. The git GUI is a faster and more convenient method for checking out the HiFi-2 snapshot. To check out the snapshot_2+SMP branch simply run the command 'git gui' and then pull down the branch->create menu. Next select <>Match Tracking Branch Name and click on origin/snapshot_2+SMP. Finally hit the Create Button.

   $ git gui                                                                        
      [Branch] -> Create...                                                                  
         <> Match Tracking Branch Name                                                     
         <> Tracking Branch                                                                 
               origin/snapshot_2+SMP                                                         
         [Create]                                                                            
     [Reposirory]--> Quit                                                                    

If there are issues installing git, as a last resort, an alternative is ftp (may not always get updated, is currently our of date, waste disk space, so may be dropped at some point):

        http://www.linux-xtensa.org/pub/snapshots/buildroot-xtensa-smp.2-Nov-2009.tar.gz         [NOTE: TO BE UPDATED]

Installing the Linux Kernel Snapshot

To install the Linux kernel environment (kernel src, config, and HiFi-2 kernel U-Boot image), cd to a location with a few GB of available disk space, and do:

   $ git clone git://git.linux-xtensa.org/git/kernel/xtensa-2.6.29-smp.git
   $ cd kernel/xtensa-2.6.29-smp

   $ git branch --track snapshot_2+SMP origin/snapshot_2+SMP                               [NOTE: The snapshot_2+SMP-stable so far appears to be a bit better]
   $ git checkout snapshot_2+SMP

The last two lines checkout the latest branch (preconfigured for the 3-core HiFi2 on the LX200). There is also a more up-to-date branch named snapshot_2+SMP-stable that has more recent kernel bug-fixes from kernel.org but it hasn't been tested as extensively but so far may be show to be a bit more stable than the well tested snapshot_2+SMP branch when memory gets tight under very heavy loads. This preconfigured 3-core HiFi2 branch has a few NFS bug fixes but nothing that immediately appears to have been a problem in this environment. Test up to now appear to be a bit better under heavy memory congestion. If you want to use this branch use the following git commands:

   $ git branch --track snapshot_2+SMP-stable origin/snapshot_2+SMP-stable
   $ git checkout snapshot_2+SMP-stable
   

As in the build root case, you can also checkout the branch easily from via git gui using the same procedure mentioned above.

Now, assuming we are still in the kernel xtensa-2.6.29-smp directory copy the kernel U-Boot Image (uImage) to the tftp directory; Ex:

   $ cp arch/xtensa/boot/uImage /tftpboot/uImage.xtensa-2.6.29-smp.test_mmuhifi_c3          [Note: You may have to make dir /tftpboot]

NOTE: On some system, like Fedora Core 9, the tftpboot directory has been moved to /var/lib/tftpboot. In this case we recommend that you just added a symbolic pointer from /etc to /var/lib/tftpboot:

   $ su
   # cd /etc
   # ln -s /var/lib/tftpboot/ tftpboot
   # ls -ld tftpboot
       lrwxrwxrwx 1 root root 18 2009-11-23 21:14 tftpboot -> /var/lib/tftpboot/
   #

Setting up a TFTP Server to provide the Linux kernel to U-Boot

The TFTP service is part of the xinetd and is installed on Fedora workstations. You can see that it's installed with the check config command which manages the /etc/rc.d/init.d startup scripts and with the yum search command:

    $ chkconfig --list
       NetworkManager  0:off   1:off   2:off   3:off   4:off   5:off   6:off
       NetworkManagerDispatcher        0:off   1:off   2:off   3:off   4:off   5:off   6:off
       acpid           0:off   1:off   2:off   3:on    4:on    5:on    6:off
       .
       .
       .
       xfs             0:off   1:off   2:on    3:on    4:on    5:on    6:off
       xinetd          0:off   1:off   2:off   3:on    4:on    5:on    6:off
       ypbind          0:off   1:off   2:off   3:on    4:on    5:on    6:off
       yum             0:off   1:off   2:off   3:off   4:off   5:off   6:off

       xinetd based services:
               amanda:         off
               auth:           off
               .
               .
               .
               rsync:          off
               tftp:           on                                                                 [NOTE that tftp is enabled]
               time:           off
               time-udp:       off
               uucp:           off
      $
      $
      $
      $ yum search tftp-server
       Loading "installonlyn" plugin
       Searching Packages:
       .
       .
       .
       Reading repository metadata in from local files
       .
       .
       .
       tftp-server.i386                         0.41-1.2.1             installed     [NOTE that tftp server is installed as part of the inet daemon]
       Matched from:
       tftp-server
       The Trivial File Transfer Protocol (TFTP) is normally used only for
       booting diskless workstations.  The tftp-server package provides the
       server for TFTP, which allows users to transfer files to and from a
       remote machine. TFTP provides very little security, and should not be
       enabled unless it is expressly needed.  The TFTP server is run from
       /etc/xinetd.d/tftp, and is disabled by default on Red Hat Linux systems.
     $

TFTP is not normally enabled, to enable it just edit the file /etc/xinetd.d/tftp and change the disable field to no:

       # default: off
       # description: The tftp server serves files using the trivial file transfer \
       #       protocol.  The tftp protocol is often used to boot diskless \
       #       workstations, download configuration files to network-aware printers, \
       #       and to start the installation process for some operating systems.
       service tftp
       {
               socket_type             = dgram
               protocol                = udp
               wait                    = yes
               user                    = root
               server                  = /usr/sbin/in.tftpd                                [NOTE: /var/lib/tftpboot on Fedora Core 9]
               server_args             = -s /tftpboot
               disable                 = no
               per_source              = 11
               cps                     = 100 2
               flags                   = IPv4
       }

Setting up an NFS Server to export the Root Filesystem

The LX200 board running Linux needs to mount its root file-system over NFS. This file system was built using buildroot into a compressed cpio format file, and left in:

   buildroot-xtensa-HiFi2-Snapshot/buildroot-xtensa-smp/binaries/HiFi-2/rootfs.xtensa_test_mmuhifi_c3.cpio.gz

We will also be adding two additional small files-systems to make your development environment more comfortable and less time consuming to get started:

   /usr/default                                                                    [Home Directory for user 'default']
   /usr/local                                                                      [File system to place enhancements not done by buildroot]

Pick a place on your workstation to export your boards file-systems and unpack the cpio and tar files. For example here we will export three files-systems in /export:

   /exports/LINUX_ROOT.HiFi-2_DemoBoard.buildroot-xtensa-smp
   /exports/hifi-2_home_default
   /exports/hifi-2_usr_local

Here's and example of unpacking the three files-systems:

   $ cd buildroot-xtensa-HiFi2-Snapshot/buildroot-xtensa-smp/binaries/HiFi-2 [Getting binary files in buildroot git repository]
   $
   $ gunzip rootfs.xtensa_test_mmuhifi_c3.cpio.gz                            [Uncompressing file-system cpio file]
   $ gunzip hifi-2_home_default.tar.gz                                       [Uncompress /home/default tar ball]
   $ gunzip hifi-2_usr_local.tar.gz                                          [Uncompress /usr/local tar ball]
   $
   $ WHERE=$PWD
   $ mkdir -p /exports/LINUX_ROOT.HiFi-2
   $
   $ cd /exports/LINUX_ROOT.HiFi-2
   $ cpio -i < $WHERE/rootfs.xtensa_test_mmuhifi_c3.cpio
   $
   $ cd /export
   $ tar xf hifi-2_home_default.tar                                          [Tar in boards /home/default for export]
   $ tar xf hifi-2_usr_local.tar                                             [Tar in boards /usr/local for export]

Next add two lines to /etc/exports:

   /exports                *(rw,no_root_squash,sync,no_wdelay)                     [Boards File-systems]
   /export                 *(rw,no_root_squash,sync,no_wdelay)                     [Buildroot source code]

and restart you nfs services:

   $ /etc/rc.d/init.d/nfs restart

or

   $ /sbin/chkconfig nfs on

The showmount command should show your NFS file systems now being exported:

   $ showmount -e
     Export list for mypc.foobar.com:
     /export  *
     /exports *
   $

Configuring U-Boot to Boot Linux

Your LX200 board should have arrived with U-Boot installed in the flash ready to use. If it fails to boot U-Boot or you happen to have a board without it there are instructions at http://wiki.linux-xtensa.org/index.php/Setting_up_U-Boot to make it easy to install.

The board has a DIP switch (next to the power on/off switch) that provides the 6 LSBs of the Ethernet MAC, in switch positions 1 thru 6.

             DIP Swithes for MAC: 1 2 3 4 5 6 7 8    ethaddr=00:50:C2:13:6f:0a
             Little Endian:       0 1 0 1 0 0 * *
                                                ^
                                                |
                                                +------ Enables booting U-Boot from Flash

DIP switch 8 should be shipped in the ON position to enable U-Boot booting from flash. See Sections 4.2.3 and 4.2.4 of the Tensilica Avnet (XT-AV200) Board User's Guide for details. Make sure to select a unique MAC address for you board.

Next, connect a serial interface to a text based terminal emulation program, set to 38400 bps, no parity, 1 stop bit, no handshaking. For an example of setting minicom for this, see here.

When you initially power on your LX200 board it will come with a very long wait period before booting and will be waiting to be configured. You can also hit one of the blue buttons next to the blue LED that's next to the PCI connector to reset the board.

The minicom session should look like the following:

   U-Boot 2009.08 (Nov 15 2009 - 22:03:26)
   
   CPU:    Xtensa test_mmuhifi_c3 at 41.6777 MHz
   Board:  XT-AV200: Avnet board + Xilinx LX200 FPGA + Tensilica bitstream
   SysRAM: 96 MB
   Flash: 16 MB
   In:    serial
   Out:   serial
   Err:   serial
   MAC:    00:50:C2:13:6f:07
   IP:     192.168.11.105
   open_ethernet
   Autobooting in 999999 seconds, press <SPACE> to stop <SPACE>
    
   U-Boot> printenv
   baudrate=38400
   ethaddr=00:50:C2:13:6f:07
   ethact=open_ethernet
   serverip=192.168.11.55
   nfsroot_server=192.168.11.55
   root-path=/exports/LINUX_ROOT.HiFi-2
   bootargs_using_bootp=console=ttyS0,38400 ip=bootp root=nfs coredump_filter=0xff
   bootcmd=tftpboot; bootm
   netmask=255.255.255.0
   gatewayip=192.168.11.1
   nfs_boot_args=root=/dev/nfs rw nfsroot=192.168.11.55:/exports/LINUX_ROOT.HiFi-2
   bootfile=uImage.xtensa-2.6.29-smp.test_mmuhifi_c3-stable
   autostart=no
   bootdelay=999999
   ipaddr=192.168.11.105
   misc_boot_args=debug coredump_filter=0xff
   hostname=HiFi-2
   nfsaddrs=192.168.11.105:192.168.11.55:192.168.11.1:255.255.255.0:HiFi-2
   bootargs=console=ttyS0,38400 ip=192.168.11.105:192.168.11.55:192.168.11.1:255.255.255.0:HiFi-2 root=/dev/nfs rw nfsroot=192.168.11.55:/exports/LINUX_ROOT.HiFi-2 debug coredump_filter=0xff
   stdin=serial
   stdout=serial
   stderr=serial
   ver=U-Boot 2009.08 (Nov 15 2009 - 22:03:26)
    
   Environment size: 788/131068 bytes
   U-Boot>

Here's how to configure U-Boot to automatically boot the Linux kernel on power-up (using the root file system exported over NFS as described further above). You need to configure UBoot with the IP addresses that are practical in your environment. When using BOOTP or DHCP many of the IP addresses are in the DHCP config file. Here we first present the simple case where all of the addresses are provided in the U-Boot environment variables:

   U-Boot> setenv serverip        192.168.11.55                                                         [TFTP server IP Address: My Workstation]
   U-Boot> setenv nfsroot_server  192.168.11.55                                                         [Root NFS Servers IP Address: My Workstation]
   U-Boot> setenv ipaddr          192.168.11.105                                                        [HOST IP address]
   U-Boot> setenv netmask         255.255.255.0                                                         [Network Mask for a Internet Class C local network]
   U-Boot> setenv gatewayip       192.168.11.1                                                          [Gateway address for default route]
   U-Boot> setenv bootfile        uImage.xtensa-2.6.29-smp.test_mmuhifi_c3                              [File to fetch with TFTP and pass to bootm]
   U-Boot> setenv root-path       /export2/DC_B_330HiFi_3Core_MMU/LINUX_ROOT.HiFi-2                     [Location of root filesystem on NFS Server; Limit ~50 bytes]
   U-Boot> setenv nfs_boot_args   root=/dev/nfs rw nfsroot=${nfsroot_server}:${root-path}               [NFS Args used in bootargs]
   U-Boot> setenv hostname        HiFi-2_NFS_Based                                                      [Hostname]
   U-Boot> setenv nfsaddrs        ${ipaddr}:${nfsroot_server}:${gatewayip}:${netmask}:${hostname}       [IP addresses needed by NFS when not using DHCP or BOOTP]
   U-Boot> setenv misc_boot_args  debug coredump_filter=0xff                                            [Enable kernel debug messages and core files on a SEGV sig] 
   U-boot> setenv bootargs        console=ttyS0,38400 ip=${nfsaddrs} ${nfs_boot_args} ${misc_boot_args} [Args passed to Linux while booting with DHCP proto]
   U-boot> setenv bootcmd         tftpboot\; bootm                                                      [Boot Linux after fetching it with TFTP]
   U-Boot> setenv bootdelay       5                                                                     [Delay 5 seconds before booting automatically]
   U-Boot> setenv autostart       yes                                                                   [Boot automatically on power-up/reset]
   U-Boot>

Alternatively, if you don't feel like setting up an NFS exports you can could use a root filesystem simply located in the kernel RAM. In this case only TFTP will be used on the local Ethernet to load the kernel. This could be set up with these commands:

   U-Boot> setenv serverip        192.168.11.55                                                           [TFTP server IP Address: My Workstation] 
   U-Boot> setenv ipaddr          192.168.11.105                                                          [HOST IP address]
   U-Boot> setenv netmask         255.255.255.0                                                           [Network Mask for a Internet Class C local network]
   U-Boot> setenv gatewayip       192.168.11.1                                                            [Gateway address for default route]
   U-Boot> setenv bootfile        uImage.xtensa-2.6.29-smp.test_mmuhifi_c3.ramfs                          [File to fetch with TFTP and pass to bootm]
   U-Boot> setenv root-path       /export2/DC_B_330HiFi_3Core_MMU/LINUX_ROOT.HiFi-2                       [Location of root filesystem on NFS Server; Limit ~50 bytes]
   U-Boot> setenv ramfs_boot_args root=/dev/ramfs                                                         [RAMFS Args used in bootargs]
   U-Boot> setenv hostname        HiFi-2_RamFS_Based                                                      [Hostname]
   U-Boot> setenv nfsaddrs        ${ipaddr}:${nfsroot_server}:${gatewayip}:${netmask}:${hostname}         [IP addresses needed by NFS when not using DHCP or BOOTP]
   U-Boot> setenv misc_boot_args  debug coredump_filter=0xff                                              [Enable kernel debug messages and core files on a SEGV sig] 
   U-boot> setenv bootargs        console=ttyS0,38400 ip=${nfsaddrs} ${ramfs_boot_args} ${misc_boot_args} [Args passed to Linux while booting with DHCP proto]
   U-boot> setenv bootcmd         tftpboot\; bootm                                                        [Boot Linux after fetching it with TFTP]
   U-Boot> setenv bootdelay       5                                                                       [Delay 5 seconds before booting automatically]
   U-Boot> setenv autostart       yes                                                                     [Boot automatically on power-up/reset]
   U-Boot>

You can also set up your dhcp server with your domain information and boot with much less information and it's no longer necessary to edit the targets /etc/resolve.conf with your domain server information:

   U-Boot> setenv bootargs_using_bootp console=ttyS0,38400 ip=bootp root=nfs coredump_filter=0xff       [Args passed to Linux while booting with BOOTP proto]
   
   U-Boot> setenv bootargs_using_bootp console=ttyS0,38400 ip=dhcp  root=nfs coredump_filter=0xff       [Args passed to Linux while booting with DHCP  proto]

If you want to boot with bootp or dhcp you may want your /etc/dhcp.conf file to look something like this:

   allow bootp;
   boot-unknown-clients off;
   ignore unknown-clients;
   not authoritative;
   ddns-update-style ad-hoc;
    
   option domain-name "hq.tensilica.com";
    
   subnet 192.168.11.0 netmask 255.255.255.0 {
       default-lease-time 2592000;     # 30 days
       max-lease-time 31557600;        # 1 year
       next-server = option dhcp-server-identifier;
       option routers 192.168.11.1;
       group {
               use-host-decl-names on;
                   ##
                   ## RTOS13   192.168.11.105: HelloSoft LX200 SMP Board on Piet's Desk
                   ##              DIP Swithes for MAC: 1 2 3 4 5 6 7 8    ethaddr=00:50:C2:13:6f:0F
                   ##              Little Endian:       1 1 1 1 0 0 * *
                   ##          Running HiFi-2
                   ##
                   ## hifi2.hq.tensilica.com:192.168.11.105::0x9b0ba8c0
    
                   host hifi2 {
                       hardware ethernet 00:50:c2:13:6f:07;
                       fixed-address hifi2.hq.tensilica.com;
                       next-server pdelaney_fc5.hq.tensilica.com;
                           option root-path "/exports/LINUX_ROOT.HiFi-2
                       option domain-name "hq.tensilica.com";
                       option domain-name-servers 192.168.15.20,192.168.15.21;
                   }
       }
   }

For more information on setting up the Linux Kernel boot parameters see the http://www.linuxdocs.org/HOWTOs/BootPrompt-HOWTO-3.html webpage.

Tailoring your system prior to Booting

There are a few tweaks we mentioned that developers have found convenient to add to the the root file-system before booting. As an initial environment for developing we are suggesting to mounting /home/default and /usr/local files-systems which have a number of files useful for getting started.

   $ cd /export/hifi-2_home_default
   $ ls -l
   drwxrwxrwx   12 root     root         4096 Dec  1 23:33 Audio_Tests/
   drwxr-xr-x    2 default  default      4096 Oct 28 17:46 Files/
   drwxr-xr-x    6 root     root         4096 Dec  2 02:46 LTP_Test/
   drwxr-xr-x    2 root     root         4096 Nov 20 15:13 Music/
   -rw-r--r--    1 10415    10000         841 Nov 20 01:18 SSH_Keys
   drwxr-xr-x    2 root     root         4096 Nov 13 12:14 Tests/
   drwxr-xr-x    2 10415    10000        4096 Nov 19 23:23 hifitest/
   drwxr-xr-x    5 root     root         4096 Dec  2 05:33 mplayer_packages/
   -rwxr-xr-x    1 10415    10000         544 Dec  2 03:01 save_root_files*
   -rw-r--r--    1 root     root        37888 Dec  2 03:13 saved_root_files.tar

Notice a file tar ball in the /home/default file system called saved_root_files.tar. This is a tar file of files that developers have found convenient to add and replace on the root file system after adding a new buildroot file system. Here is a list of the files and a brief explanation on why it's convenient to add or replace them:

   root/.bash_profile                           [added 'ulimit -c unlimited to allow core dumps to be created]
   root/.bashrc
   etc/profile                                  [added 'ulimit -c unlimited to allow core dumps to be created]                                        
   etc/fstab                                    [Tells the system how to mount extra NFS file systems like /home/default]
   etc/init.d/S90local                          [Mounts /home/default]
   etc/resolv.conf                              [Your locations of DNS servers; used when your not using DHCP to boot the kernel]
                                                [NOTE: restore symlink  /etc/resolv.conf -> /proc/net/pnp if using DHCP]
   etc/TZ                                       [Your time zone, currently set to California TZ]
   etc/dropbear/dropbear_rsa_host_key           [Old DropBrer keys, useful if you prefer Dropbear of sshd]
   etc/dropbear/dropbear_dss_host_key           [Old DropBrer keys, useful if you prefer Dropbear of sshd]
   etc/ssh_config                               [Typically tailored with things like allowing root logins via ssh]
   etc/ssh_host_dsa_key                         [sshd keys - Takes 30 minutes to generate, saves time on initial boot]
   etc/ssh_host_dsa_key.pub                     [sshd keys - Takes 30 minutes to generate, saves time on initial boot]
   etc/ssh_host_key                                            
   etc/ssh_host_key.pub
   etc/ssh_host_rsa_key
   etc/ssh_host_rsa_key.pub
   etc/sshd_config                              [Typically tailored with things like allowing root logins via ssh]
   etc/rndc.key                                                 
   etc/random-seed                              [Generated during 1st boot]
   etc/passwd                                   [Changed root and default user's shell to bash; runs std bash RC files to set ulimits; adds /usr/local/bin to search path]
   etc/shadow                                   [Changed default and root users login password to 'linux1', needed to ssh to the board]
   exports/                                     [The path to where the board can mount extra file systems like /home/default.
   usr/local                                    [Makes /usr/local so it can be mounted on; it has local additions, including /usr/local/src]
   codecs                                       [Makes /codecs for a NFS partition with Tensilica HiFi-2 Codecs to be mounted; the file-system should contain ...
                                                 ... /codecs/xa_hifi2_l32r_LE5_pic_mp3_dec_lib_3_1_api_1_15_lib.tgz
                                                 ... /codecs/xa_hifi2_l32r_LE5_pic_aacplus_v2_dec_lib_2_2_api_1_15_lib.tgz ]
    

Now lets assume your going to stay with mosts of these changes and modify a few of them after tar'ing in these changes to the root file-system. So here we add the tar ball files to the boards root filesystem.

   $ cd /exports/LINUX_ROOT.HiFi-2
   $ tar xf /exports/hifi-2_home_default/saved_root_files.tar

This is a good time to edit a few files on the boards file system before booting it.

   $ cd /exports/LINUX_ROOT.HiFi-2
   $ vi etc/resolv.conf                   [Place your domain information if not using a DHCP boot]
                                                [Restore symlink resolv.conf -> /proc/net/pnp if using DHCP]
   $ vi etc/fstab                         [Change fstab entry for boards root filesystem, and others to your taste]
   $ vi etc/init.d/S90local               [You might want to disable mounting of non-root NFS file systems ...
                                                 ... on the 1st Boot and add this once you try it manually]

Booting Linux for the 1st Time

We should now be ready to boot linux on your LX200. You have exported the root file-system and made the kernel available to a TFTP server. Now let's start with hitting the reset button on the LX200 and it should auto-boot the kernel, resulting in output such as this example log.

Tailoring your system prior to developing for HiFi 2

To make your experience more pleasant we suggest you tailoring your environment. Here are some of the changes that we have found helpful and provided in the saved_root_files:

  1. Added a root password to that you can login with ssh.
  2. Running rdate with an ntp server on booting.
  3. Adding NFS mounts to /etc/fstab for your code and buildroot code.
  4. Copy in previous ssh server encryption keys to /etc/dropbear to speed up your initial boot.
  5. Mount a 'default' user home directory with:
     a. Linux Test Suite pre-patch to test the system
     b. Audio test example files
     c. Copies of Mplayer and its Plug-in build environment from Buildroot modified slightly to make installation easy.
     d. Misc audio test programs.
  6. Mounting Tensilica HiFi-2 Codecs to easily get mplayer working with HiFi-2 TIE instructions.

Building Linux Applications

Building Linux Applications Using GCC on the Host

You can use the open source toolchain included in the buildroot tree.

Given the location of the buildroot tree and the name of the core:

  $ setenv BUILDROOT_DIR  /export/src/HiFi-2_DemoBoard/buildroot-xtensa-HiFi2-Snapshot.12
  $ setenv CORENAME       test_mmuhifi_c3

You can either set the PATH and invoke tools prefixed with xtensa_${CORENAME}-linux- :

  $ setenv PATH   ${BUILDROOT_DIR}/build_xtensa_${CORENAME}/staging_dir/usr/bin:${PATH}
  $ xtensa_test_mmuhifi_c3-linux-gcc -g hello.c -o hello
  $ xtensa_test_mmuhifi_c3-linux-gdb hello

or alternatively invoke the tools with absolute paths:

  $ ${BUILDROOT_DIR}/build_xtensa_test_mmuhifi_c3/staging_dir/usr/bin/xtensa_test_mmuhifi_c3-linux-gcc -g hello.c -o hello
  $ ${BUILDROOT_DIR}/build_xtensa_test_mmuhifi_c3/staging_dir/usr/bin/xtensa_test_mmuhifi_c3-linux-gdb hello

Building Linux Applications Using GCC on the Target

This is the simplest. (Much slower of course at 45 MHz across a slow Ethernet link than on a workstation, but very convenient.) Just login to the target system and use the native gcc.

Building Linux Applications Using XCC (Xtensa Tools)

There are two approaches to compiling with Tensilica's XCC compiler (part of Xtensa Tools). The normal one, described below, is to initially setup a virtual core that has built-in references to the library and include files for the target Linux system. Alternatively, one could skip this initial setup and just use Xtensa Tools to create object files and link them using host or target GCC tools. However, such objects must be built without dependencies on such things as the C library, which can be harder than it sounds (for example, flags and structures, such as open()'s O_EXCL and stat()'s struct stat, must be avoided because their definitions likely differ between the Xtensa Tools' default C library and the Linux uClibc library). (Note: Codecs such as MP3 and AAC are typically written in C with TIE extensions and can only be compiled with XCC.)

Section 4.3 of the latest Xtensa OSKit Guide (from Tensilica's RC-2009.0 release) describes how to setup XCC to compile Linux applications. For full details, see the guide. A summary follows.

Initial Setup

The XTENSA_TOOLS_ROOT, XTENSA_ROOT, BUILDROOT_DIR, and TARGET_SYSROOT environment variables must be set according to where things were installed; values shown here are for illustration only. The CORENAME variable, set correctly below for this board, reflects the name of the core as known to open source tools (as opposed to XTENSA_CORE which is the core name as known to Xtensa Tools; both happen to match here).

   $ setenv USER              someuser
   $ setenv XTENSA_ROOT       /home/${USER}/Xplorer/XtDevTools/install/builds/RC-2009.0-linux/test_mmuhifi_c3
   $ setenv XTENSA_TOOLS_ROOT /home/${USER}/Xplorer/XtDevTools/install/tools/RC-2009.0-linux/XtensaTools
   $ setenv TARGET_SYSROOT    /exports/LINUX_ROOT.HiFi-2
   $ setenv BUILDROOT_DIR     /export/src/HiFi-2_DemoBoard/buildroot-xtensa-HiFi2-Snapshot
   
   $ setenv CORENAME         test_mmuhifi_c3
   
   $ cd ${BUILDROOT_DIR}
   $ ${XTENSA_ROOT}/xtensa-elf/src/linux/bin/xt-xcc-linux-install                                \
       --sysroot=./build_xtensa_${CORENAME}/staging_dir'                                         \
       --linux-gcc=./build_xtensa_${CORENAME}/staging_dir/usr/bin/xtensa_${CORENAME}-linux-gcc

Regular Use

Assuming the above completed successfully, you can now build applications using Xtensa Tools. First set the usual environment variables (assuming values of XTENSA_ROOT and XTENSA_TOOLS_ROOT used earlier):

   $ setenv XTENSA_CORE      default
   $ setenv XTENSA_SYSTEM    ${XTENSA_ROOT}-linux/config
   $ setenv PATH             ${XTENSA_TOOLS_ROOT}/bin:${PATH}

Now you can use Xtensa Tools to assemble, compile, and link applications for the Linux target specified during setup. For example:

   $ echo '#include <stdio.h>' > hello.c
   $ echo 'int main() {printf("Hello!\\n");return 0;}' >> hello.c
   $ xt-xcc -g hello.c -o hello

Then copy it where the target can see it:

   $ cp hello ${TARGET_SYSROOT}/root                             [NOTE: This step isn't necessary if your src file system is mounted on the targer; Ex: /export]

And run it on the target:

   [root@hifi ~]# /root/hello
   Hello!
   [root@hifi ~]#

Here's a more interesting example that uses Tensilica TIE features. (This cannot be compiled using GCC.)

   $ cd ${TARGET_SYSROOT}/home/default/Audio_Tests
   $ xt-xcc -g hifitest.c -o hifitest

In a ssh termulator window on the board you can now run hifitest:

   [root@hifi ~]# cd /home/default/Audio_Tests/
   [root@hifi Audio_Tests]# ./hifitest
   cnt:0x0, pid:23178; Eatting cpu; time:0 <control-C>
   
   [root@hifi Audio_Tests]#

Here is the source code for the hifitest.c source file used above.

Limited (No Setup) Use of Xtensa Tools for Linux Targets

Below we illustrate compiling a simple audio test program on a workstation. We start by referring to the XTENSA tools build by Xplorer, putting XCC into our search path and set the standard XTENSA_* environment variables. For example:

   setenv XTENSA_CORE      test_mmuhifi_c3
   setenv XTENSA_ROOT      /home/pdelaney/Xplorer/XtDevTools/install/builds/RC-2009.0-linux/test_mmuhifi_c3
   setenv XTENSA_SYSTEM    /home/pdelaney/Xplorer/XtDevTools/install/builds/RC-2009.0-linux/test_mmuhifi_c3/config
   setenv XTENSA_TOOLS     /home/pdelaney/Xplorer/XtDevTools/install/tools/RC-2009.0-linux/XtensaTools/bin
    
   setenv PATH ${XTENSA_TOOLS}:${PATH}
   
   
   [piet@fc9desktop Tests]      $ cd /exports/hifi-2_home_default/Audio_Tests                           [NOTE: This is being done on a Workstation]
   [piet@fc9desktop Audio_Tests]$ xt-xcc -g3 -O0 -fPIC -c hifitest.c

Next we link the object on the LX200 board and run gdb on the TIE enhanced code:

  [root@hifi Audio_Tests]# gcc -g hifitest.o -o hifitest
  [root@hifi Audio_Tests]# ./hifitest
                            cnt:0x0, pid:4640; Eatting cpu; time:0
                            cnt:0x0, pid:4640; Eating Tie; time:7
  ^C
  [root@hifi Audio_Tests]# gdb ./hifitest                                                               [NOTE: This is being done on the LX200 board]
  GNU gdb 6.6
  Copyright (C) 2006 Free Software Foundation, Inc.
  GDB is free software, covered by the GNU General Public License, and you are
  welcome to change it and/or distribute copies of it under certain conditions.
  Type "show copying" to see the conditions.
  There is absolutely no warranty for GDB.  Type "show warranty" for details.
  This GDB was configured as "xtensa_test_mmuhifi_c3-linux-uclibc"...
   Using host libthread_db library "/lib/libthread_db.so.1".
  (gdb) break main
  Breakpoint 1 at 0x400401: file /exports/default/Audio_Tests/hifitest.c, line 20.
  (gdb) run
  Starting program: /home/default/Audio_Tests/hifitest 
   
  Breakpoint 1, main (argc=1, argv=0x3fb3fab4)
      at /exports/default/Audio_Tests/hifitest.c:20
  20	     time_t time0 = time(NULL);
  (gdb) step
  21	  time_t time1 = time(NULL);

Compiling Generic GPL Packages

For your development you may want to add a few GPL packages that you find helpful. This can be done on the LX200 just as you would on a normal workstation, though much slower. For example here we configure and build a few common GPL packages with the standard:

  $ ssh root@hifi
  [root@hifi ~] # cd /usr/local/src
  [root@hifi src] # mkdir <package>
  [root@hifi src] # wget <url_to_package>
  [root@hifi src] # gunzip <package.tgz>
  [root@hifi src] # cd package
  [root@hifi <package> ] # .configure
  [root@hifi <package> ] # make
  [root@hifi <package> ] # make install

Here are two examples, the invaluable strace and vim GPL packages:

 Building the Strace Package

 Building the vim Package

This can be a useful effort prior to adding a package to buildroot or for compiling packages with debug enabled. For example on of our developers compiled uClibc with -g to debug problems in this package.

Compiling the Mplayer Plugins and linking them with MPEG-1 Audio Layer 3 (MP3) and MPEG-4 AAC Codecs

Mplayer is provided as an example environment for developing and testing Codecs and HiFi 2 software. There are two ways to build Mplayer and the plug-in modules that use the codecs. The buildroot tree (pulled with git) has a copy of mplayer and the plugins that can be built in the snapshot via 'make menuconfig'. This is a good environment to use once codecs are developed and debugged.

To facilitate development the mplayer packages can be copied to your NFS mounted development environment. From there you can just configure mplayer to compile on the board and debug mplayer and your codecs with gdb locally.

In the default user home directory we have a directory /home/default/buildroot_mplayer_stuff with a copy of three of the mplayer packages:

   [root@hifi buildroot_mplayer_stuff]# ls -l
    drwxr-xr-x   34 root     root         4096 Nov 10 05:01 MPlayer-1.0rc2/
    drwxr-xr-x    4 root     root         4096 Nov 10 01:36 mplayer_hifi2_aacplus_v2_plugin/
    drwxr-xr-x    3 root     root         4096 Nov 10 00:57 mplayer_hifi2_mp3_plugin/

they were simply copied from the buildroot-xtensa-HiFi2-Snapshot.2/package directory.

To get your development environment ready to compile the mplayer plug-ins you need to configure Mplayer to use the local C compiler and linker:

   # cd /home/default/buildroot_mplayer_stuff/MPlayer-1.0rc2/
   # CFLAGS="-g3" ./configure

This will take about 15 minutes to configure. After that you can build the plugins or mplayer. If you want to recompile mplayer it's likely best/necessary to use the same args to .configure as used by buildroot:

       .CFLAGS="-g3" ./configure \
               --prefix=/usr \
               --confdir=/etc/mplayer \
               --with-extraincdir=/usr/include \
               --with-extralibdir=/lib \
               --disable-gui \
               --enable-mad \
               --enable-fbdev \
               --disable-mencoder \
               --disable-dvdnav \
               --disable-dvdread \
               --disable-dvdread-internal \
               --disable-libdvdcss-internal \
               --disable-big-endian \
               --disable-nemesi \
               --disable-tv \
               --enable-dynamic-plugins

We are currently able to compile mplayer on the LX200 but due to space limitations it's not possible to compile it -O0.

Now, let's focus on compiling linking the plugins. They are a nice example of compiling an audio application on the LX200.

We modified the plugin Makefile slightly, and they are available in /home/default/mplayer_packages. These additions just instruct make how to fetch the codecs and build and install the plugins as explained in the Chapter 7 of the Linux HiFi application note. With these Makefile additions and the Tensilica codecs available in the /plugins directory is very easy.

For example the mp3 plugin has this addition:

   # We assume Tensilica Codecs have been mounted at /codecs
   # via /etc/fstab during boot.
   #
   CODEC_PACKAGE=xa_hifi2_l32r_LE5_pic_mp3_dec_lib_3_1_api_1_15_lib
   CODEC_PACKAGE_LOCATION=/codecs
   MPLAYER_DEVEL_LOCATION=/home/default/buildroot_mplayer_stuff
    
   all: $(XA_CODEC_NAME) $(SLIBNAME) $(XA_CODEC_NAME).so
   .
   .
   .
   $(CODEC_PACKAGE).tgz:
           cp $(CODEC_PACKAGE_LOCATION)/$(CODEC_PACKAGE).tgz .
   
   $(CODEC_PACKAGE).tar:: $(CODEC_PACKAGE).tgz
           gunzip $(CODEC_PACKAGE).tgz
   
   $(XA_CODEC_NAME):: $(CODEC_PACKAGE).tar
             tar xf $(CODEC_PACKAGE).tar
   
   install::
           @-mkdir /etc/mplayer
           cp codecs.conf /etc/mplayer
           @-mkdir /usr/lib/mplayer
           cp ad_xa_mp3_dec.so /usr/lib/mplayer/
           cp xa_mp3_dec.so /usr/lib/mplayer
           chmod 755 /usr/lib/mplayer/ad_xa_mp3_dec.so
           chmod 755 /usr/lib/mplayer/xa_mp3_dec.so

The make file will be just providing a codec config file for mplayer at /etc/mplayer/codecs.conf and copying the plug-in to /usr/lib/mplayer. To install the mp3 codec plugin and mplayer config file just copy your codec that was compiled with xcc to the directory, compile it, and install. To add mp3 and aac plugins to mplayer you just type make followed by make install:

   [root@hifi mplayer_hifi2_mp3_plugin]# make
   cp /codecs/xa_hifi2_l32r_LE5_pic_mp3_dec_lib_3_1_api_1_15_lib.tgz .
   gunzip xa_hifi2_l32r_LE5_pic_mp3_dec_lib_3_1_api_1_15_lib.tgz
   tar xf xa_hifi2_l32r_LE5_pic_mp3_dec_lib_3_1_api_1_15_lib.tar
   cc -I../libavcodec -I../libavformat -I. -I.. -I../libavutil -W -Wall -O2   -pipe -g3  -D_REENTRANT -DHAVE_CONFIG_H -I/usr/include  -DNDEBUG -fvisibility=hidden -Ixa_mp3_dec/include -I../MPlayer-1.0rc2 -Ic
   xa_mp3_dec_sample_testbench.c: In function 'xa_mp3_decode_frame':
   xa_mp3_dec_sample_testbench.c:185: warning: pointer targets in passing argument 1 of 'xa_mp3_audio_read' differ in signedness
   xa_mp3_dec_sample_testbench.c:163: warning: unused variable 'j'
   xa_mp3_dec_sample_testbench.c: In function 'mp3_codec_init':
   xa_mp3_dec_sample_testbench.c:517: warning: pointer targets in passing argument 1 of 'xa_mp3_audio_read' differ in signedness
   xa_mp3_dec_sample_testbench.c: At top level:
   xa_mp3_dec_sample_testbench.c:112: warning: 'pack_32_to_24_bits' defined but not used
   cc -I../libavcodec -I../libavformat -I. -I.. -I../libavutil -W -Wall -O2   -pipe -g3  -D_REENTRANT -DHAVE_CONFIG_H -I/usr/include  -DNDEBUG -fvisibility=hidden -Ixa_mp3_dec/include -I../MPlayer-1.0rc2 -Ic
   ad_xa_mp3_dec.c: In function 'xa_mp3_audio_read':
   ad_xa_mp3_dec.c:26: warning: pointer targets in passing argument 2 of 'demux_read_data' differ in signedness
   ad_xa_mp3_dec.c: In function 'init':
   ad_xa_mp3_dec.c:42: warning: pointer targets in passing argument 1 of 'xa_mp3_decode_frame' differ in signedness
   ad_xa_mp3_dec.c: At top level:
   ad_xa_mp3_dec.c:52: warning: unused parameter 'sh'
   ad_xa_mp3_dec.c:56: warning: unused parameter 'arg'
   ad_xa_mp3_dec.c:78: warning: unused parameter 'sh_audio'
   cc -I../libavcodec -I../libavformat -I. -I.. -I../libavutil -W -Wall -O2   -pipe -g3  -D_REENTRANT -DHAVE_CONFIG_H -I/usr/include  -DNDEBUG -fvisibility=hidden -Ixa_mp3_dec/include -I../MPlayer-1.0rc2 -Im
   cc -I../libavcodec -I../libavformat -I. -I.. -I../libavutil -W -Wall -O2   -pipe -g3  -D_REENTRANT -DHAVE_CONFIG_H -I/usr/include  -DNDEBUG -fvisibility=hidden -Ixa_mp3_dec/include -I../MPlayer-1.0rc2 -Ie
   [root@hifi mplayer_hifi2_mp3_plugin]#

   [root@hifi mplayer_hifi2_mp3_plugin]# make install
   mkdir: cannot create directory '/etc/mplayer': File exists
   make: [install] Error 1 (ignored)
   cp codecs.conf /etc/mplayer
   mkdir: cannot create directory '/usr/lib/mplayer': File exists
   make: [install] Error 1 (ignored)
   cp ad_xa_mp3_dec.so /usr/lib/mplayer/
   cp xa_mp3_dec.so /usr/lib/mplayer
   chmod 755 /usr/lib/mplayer/ad_xa_mp3_dec.so
   chmod 755 /usr/lib/mplayer/xa_mp3_dec.so
   [root@hifi mplayer_hifi2_mp3_plugin]#

The makefile unpacked of the Tensilica mp3 codec tarball will installed the following files:

   xa_mp3_dec/
   xa_mp3_dec/README
   xa_mp3_dec/include/
   xa_mp3_dec/include/mp3_dec/
   xa_mp3_dec/include/mp3_dec/xa_mp3_dec_api.h
   xa_mp3_dec/include/xa_apicmd_standards.h
   xa_mp3_dec/include/xa_error_handler.h
   xa_mp3_dec/include/xa_error_standards.h
   xa_mp3_dec/include/xa_memory_standards.h
   xa_mp3_dec/include/xa_type_def.h
   xa_mp3_dec/test/
   xa_mp3_dec/test/build/
   xa_mp3_dec/test/build/ldscript_stream_data.txt
   xa_mp3_dec/test/build/makefile_testbench_sample
   xa_mp3_dec/test/build/paramfilesimple.txt
   xa_mp3_dec/test/include/
   xa_mp3_dec/test/include/id3_tag_decode.h
   xa_mp3_dec/test/src/
   xa_mp3_dec/test/src/xa_mp3_dec_sample_testbench.c
   xa_mp3_dec/test/src/id3_tag_decode.c
   xa_mp3_dec/test/src/stream_data.c
   xa_mp3_dec/test/src/xa_mp3_dec_error_handler.c
   xa_mp3_dec/test/test_inp/
   xa_mp3_dec/test/test_inp/compl.mp3
   xa_mp3_dec/test/test_inp/hihat.mp3
   xa_mp3_dec/test/test_out/
   xa_mp3_dec/test/test_out/force_mkdir.txt
   xa_mp3_dec/test/test_ref/
   xa_mp3_dec/test/test_ref/compl_24bit.wav
   xa_mp3_dec/test/test_ref/hihat_16bit.wav
   xa_mp3_dec/lib/
   xa_mp3_dec/lib/xa_mp3_dec.a
   xa_mp3_dec/doc/
   xa_mp3_dec/doc/HiFi2-MP3-DecoderProgrammersGuide.pdf

Now, having built and installed the mp3 plugin, do the same for the AAC codec.

   [root@hifi ~]# cd /home/default/mplayer_packages/mplayer_hifi2_aacplus_v2_plugin/
   [root@hifi mplayer_hifi2_aacplus_v2_plugin]# make
   [root@hifi mplayer_hifi2_aacplus_v2_plugin]# make install

Additional codecs can be downloaded from the mplayer web site, configured, compiled and can be installed as usual.

  http://www.mplayerhq.hu/DOCS/HTML/en/codec-installation.html

  [opencore-amr | opencore-amr]

opencore-amr builds fine and the x264-snapshot compiles completely but the Makefile and code needs to be set up for ARCH xtensa. The GPL AAC decoder, faad, has out of date autoconf files, config.sub and config.guess, need to be updated for Xtensa. This can be easily done by copying config.sub and config.guess from the x264-snapshot which had up to date versions recognizing xtensa correctly.

Add on codec install by default to /usr/local/lib and the ldconfig config file /etc/ld.so.conf needs to have /usr/local/lib added.

Lots of opportunity likely exists for optimizing these codec for Xtensa extensibility.

[TO BE DONE - Add missing C file, make clean deletes it!]

The xa_mp3_dec.a archive will be used by the Makefile in the mplayer_hifi2_mp3_plugin directory to make the mplayer plug-in. Section 6 of the 'Using Tensilica HiFi 2 Codec on Xtensa Linux with MPlayer Application Note has a detailed description of the encapsulation process used by the plug-ins.

Adding Packages and/or Codec to Buildroot

Xtensa developers provide detailed instructions on building the root filesystem and the Linux kernel.

• Instructions for building and booting Linux (buildroot).

Building a comprehensive development environment with buildroot can be a challenging experience and worthy of providing some tips on process. Here are notes of the configs used for the three menuconfigs in this 2nd snapshot provided with SMP additions:

    $ make  menuconfig
    $ make  uclibc-menuconfig
    $ make  busybox-menuconfig

[TO BE DONE - making a new tar ball of saved files, building buildroot, ...]

Known Problems being investigated, suggested that you know about and possibly avoid

 1. Using NFS mounts with default parameters causes memory congestion. Use these mount options:
     
     vers=2,rsize=4096,wsize=4096,hard,nointr,nolock,nolock,timeo=11,retrans=3,noauto
   
    this is extremely important to add to your /etc/fstab on the target.
    
 2. Can't swap over NFS yet, under extreme conditions memory can get tight and cause application to be killed.
   a. We will be trying procedure documented in U-Boot Manual to swap over NFS.
 
 3. Building the complete C development with X11 doesn't work with buildroot.
  
 4. Though Mplayer plug-in can be compiled, Mplayer can be compiled but still has a few issues:
   a. Can't be compiled -O0 due to limited memory while compiling one file,
   b. Compiler was crashing and make had to be restarted.
      We are not seeing this problem with root build on Fedore Core 9.
      Perhaps this was caused by debug kernel being enabled or LTP using all of the memory.
  
 5. U-boot has flash problems:
   a. Sectors marked Read-Only come up Writeable after a reset/reboot.
  
   b. Flashing a large number of sectors (like the kernel) sometimes
      results in an Error (Ex: Vcc) and had to be retried.
  
   c. We saw environment variables trashed on reset/reboot once.
      It's possible that U-boot in flash could get whacked
      and the board will need to be re-flashed. During weeks
      of testing we haven't seen the U-Boot environment getting whacked.
    
 6. gdb appears to be crashing on target when debugging 
    on latest root with uclibc left unstriped and with debug;
    core dump sent to maxim.
     
 7. U-Boot was hanging periodically when loading the kernel with
    tftp; appears to have be worse when network activity is high.
    This problem also seems to have gone away in the past few weeks.
    It may have been a duplication with MAC addresses.
  
 8. 'top' command only shows all cpu's or cpu0; cpu 1 and 2 missing.
              
 9. Program dore dump require ulimit -c to be set but root uses /bin/sh
    which is a link to bash but causes it to skip running the bash
    startup scripts. Changing root to /bin/bash seems to mess up
    ssh logins.
   
 10. For kernel to be compiled on the LX200 (for self checking:
     a. Xtensa makefile needs to be fixed:
          CC      init/do_mounts.o
          LD      init/mounts.o
        /bin/sh: xtensa_test_mmuhifi_c3-linux-uclibc-ld: command not found
        make[1]: *** [init/mounts.o] Error 127
      
     b. Need to add ncurses-devel package for 'make menuconfig'
  
   
 11. The busybox vesion of vi doesn't work very good, we are using symbolic pointer
    
      /usr/local/bin/vi ---> /usr/local/bin/vim
    
      /usr/local/bin is searched first via bash profile and rc. 
      The vim version works great and doesn't seem to use very much memory.
  
  12. mplayer codecs by default install to /usr/local/lib but
      the ldconfig config file needs to be updated to search /usr/local/lib. 
          Ex:
               /etc/ld.so.conf:
                    # /usr/local/src/faad2-2.7/:
                    #               libfaad.a         libfaad.la        libfaad.so@
                    #               libfaad.so.2@     libfaad.so.2.0.0* libmp4ff.a
                    #
                    /usr/local/lib
       
      /etc/ld.so.conf.d exist but is being ignored by ldconfig even if included via ld.so.conf:
               include ld.so.conf.d/*.conf
      
      REMIND: update /home/default/save_root_files

Further reading

Main Xtensa Linux resources are:

• Linux/Xtensa Wiki
• Buildroot Build Instructions
• Kernel Build Instructions
• Setting up U-Boot
• Linux/Xtensa Mailing List
• http://git.linux-xtensa.org/cgi-bin/git.cgi GIT Repositories]

Thanks to

• piet
• marc
• dan
• maxim

And the rest of the people in the Linux-Xtensa mailing list, if you cannot go through some of the steps, don't hesitate to ask on the mailing list, there's always somebody willing to help you!