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| -rw-r--r-- | doc/SPL/README.am335x-network | 92 |
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diff --git a/doc/SPL/README.am335x-network b/doc/SPL/README.am335x-network new file mode 100644 index 0000000..e5a198f --- /dev/null +++ b/doc/SPL/README.am335x-network @@ -0,0 +1,92 @@ +USING AM335x NETBOOT FEATURE + + Some boards (like TI AM335x based ones) have quite big on-chip RAM and +have support for booting via network in ROM. The following describes +how to setup network booting and then optionally use this support to flash +NAND and bricked (empty) board with only a network cable. + + I. Building the required images + 1. You have to enable generic SPL configuration options (see +docs/README.SPL) as well as CONFIG_SPL_NET_SUPPORT, +CONFIG_ETH_SUPPORT, CONFIG_SPL_LIBGENERIC_SUPPORT and +CONFIG_SPL_LIBCOMMON_SUPPORT in your board configuration file to build +SPL with support for booting over the network. Also you have to enable +the driver for the NIC used and CONFIG_SPL_BOARD_INIT option if your +board needs some board-specific initialization (TI AM335x EVM does). +If you want SPL to use some Vendor Class Identifier (VCI) you can set +one with CONFIG_SPL_NET_VCI_STRING option. am335x_evm configuration +comes with support for network booting preconfigured. + 2. Define CONFIG_BOOTCOMMAND for your board to load and run debrick +script after boot: +#define CONFIG_BOOTCOMMAND \ + "setenv autoload no; " \ + "bootp; " \ + "if tftp 80000000 debrick.scr; then " \ + "source 80000000; " \ + "fi" +(Or create additional board configuration with such option). + 3. Build U-Boot as usual + $ make <your_board_name> + You will need u-boot.img and spl/u-boot.bin images to perform +network boot. Copy them to u-boot-restore.img and +u-boot-spl-restore.bin respectively to distinguish this version +(with automatic restore running) from the main one. + + II. Host configuration. + 1. Setup DHCP server (recommended server is ISC DHCPd). + - Install DHCP server and setup it to listen on the interface you +chose to connect to the board (usually configured in +/etc/default/dhcpd or /etc/default/isc-dhcp-server). Make sure there +are no other active DHCP servers in the same network segment. + - Edit your dhcpd.conf and subnet declaration matching the address +on the interface. Specify the range of assigned addresses and bootfile +to use. IMPORTANT! Both RBL and SPL use the image filename provided +in the BOOTP reply but obviously they need different images (RBL needs +raw SPL image -- u-boot-spl-restore.bin while SPL needs main U-Boot +image -- u-boot-restore.img). So you have to configure DHCP server to +provide different image filenames to RBL and SPL (and possibly another +one to main U-Boot). This can be done by checking Vendor Class +Identifier (VCI) set by BOOTP client (RBL sets VCI to "DM814x ROM v1.0" +and you can set VCI used by SPL with CONFIG_SPL_NET_VCI_STRING option, +see above). + - If you plan to use TFTP server on another machine you have to set +server-name option to point to it. + - Here is sample configuration for ISC DHCPd, assuming the interface +used to connect to the board is eth0, and it has address 192.168.8.1: + +subnet 192.168.8.0 netmask 255.255.255.0 { + range dynamic-bootp 192.168.8.100 192.168.8.199; + + if substring (option vendor-class-identifier, 0, 10) = "DM814x ROM" { + filename "u-boot-spl-restore.bin"; + } elsif substring (option vendor-class-identifier, 0, 17) = "AM335x U-Boot SPL" { + filename "u-boot-restore.img"; + } else { + filename "uImage"; + } +} + + 2. Setup TFTP server. + Install TFTP server and put image files to it's root directory +(likely /tftpboot or /var/lib/tftpboot or /srv/tftp). You will need +u-boot.img and spl/u-boot-spl-bin files from U-Boot build directory. + + III. Reflashing (debricking) the board. + 1. Write debrick script. You will need to write a script that will +be executed after network boot to perform actual rescue actions. You +can use usual U-Boot commands from this script: tftp to load additional +files, nand erase/nand write to erase/write the NAND flash. + + 2. Create script image from your script. From U-Boot build directory: + +$ ./tools/mkimage -A arm -O U-Boot -C none -T script -d <your script> debrick.scr + +This will create debrick.scr file with your script inside. + + 3. Copy debrick.scr to TFTP root directory. You also need to copy +there all the files your script tries to load via TFTP. Example script +loads u-boot.img and MLO. You have to create these files doing regular +(not restore_flash) build and copy them to tftpboot directory. + + 4. Boot the board from the network, U-Boot will load debrick script +and run it after boot. |