Hi Simon,
On Tue, Jan 27, 2015 at 9:23 AM, Simon Glass sjg@chromium.org wrote:
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 sjg@chromium.org
Reviewed-by: Bin Meng bmeng.cn@gmail.com
A minor comment below.
doc/README.x86 | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+)
diff --git a/doc/README.x86 b/doc/README.x86 index 809a291..0e4628a 100644 --- a/doc/README.x86 +++ b/doc/README.x86 @@ -164,6 +164,69 @@ 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:
+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:
+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 (Intel-specific +feature).
It would be better to document what this Intel-specific feature is in order to support this SPI bus frequency.
+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 <model>
+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
--
Regards, Bin