From 00bdd95278e189131f9b5858045c540bf0cce530 Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Tue, 27 Jan 2015 22:13:46 -0700 Subject: x86: Add some documentation on how to port U-Boot on x86 Some information has been gleaned on tools and procedures for porting U-Boot to different x86 platforms. Add a few notes to start things off. Signed-off-by: Simon Glass Reviewed-by: Bin Meng --- doc/README.x86 | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) (limited to 'doc') diff --git a/doc/README.x86 b/doc/README.x86 index ddfd75e1cd..a9105f87c0 100644 --- a/doc/README.x86 +++ b/doc/README.x86 @@ -164,6 +164,70 @@ mtrr - List and set the Memory Type Range Registers (MTRR). These are used to mode to use. U-Boot sets up some reasonable values but you can adjust then with this command. +Development Flow +---------------- + +These notes are for those who want to port U-Boot to a new x86 platform. + +Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment. +The Dediprog em100 can be used on Linux. The em100 tool is available here: + + http://review.coreboot.org/p/em100.git + +On Minnowboard Max the following command line can be used: + + sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r + +A suitable clip for connecting over the SPI flash chip is here: + + http://www.dediprog.com/pd/programmer-accessories/EM-TC-8 + +This allows you to override the SPI flash contents for development purposes. +Typically you can write to the em100 in around 1200ms, considerably faster +than programming the real flash device each time. The only important +limitation of the em100 is that it only supports SPI bus speeds up to 20MHz. +This means that images must be set to boot with that speed. This is an +Intel-specific feature - e.g. tools/ifttool has an option to set the SPI +speed in the SPI descriptor region. + +If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly +easy to fit it in. You can follow the Minnowboard Max implementation, for +example. Hopefully you will just need to create new files similar to those +in arch/x86/cpu/baytrail which provide Bay Trail support. + +If you are not using an FSP you have more freedom and more responsibility. +The ivybridge support works this way, although it still uses a ROM for +graphics and still has binary blobs containing Intel code. You should aim to +support all important peripherals on your platform including video and storage. +Use the device tree for configuration where possible. + +For the microcode you can create a suitable device tree file using the +microcode tool: + + ./tools/microcode-tool -d microcode.dat create + +or if you only have header files and not the full Intel microcode.dat database: + + ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \ + -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h \ + create all + +These are written to arch/x86/dts/microcode/ by default. + +Note that it is possible to just add the micrcode for your CPU if you know its +model. U-Boot prints this information when it starts + + CPU: x86_64, vendor Intel, device 30673h + +so here we can use the M0130673322 file. + +If you platform can display POST codes on two little 7-segment displays on +the board, then you can use post_code() calls from C or assembler to monitor +boot progress. This can be good for debugging. + +If not, you can try to get serial working as early as possible. The early +debug serial port may be useful here. See setup_early_uart() for an example. + TODO List --------- - Audio -- cgit v1.2.1