[U-Boot] [PATCH 20/39] x86: Emit post codes in startup code

[Simon Glass]

Hi Bin,

On 7 November 2014 06:37, Bin Meng <bmeng.cn at gmail.com> wrote:
> Hi Simon,
>
> On Fri, Nov 7, 2014 at 4:20 AM, Simon Glass <sjg at chromium.org> wrote:
>> On x86 it is common to use 'post codes' which are 8-bit hex values emitted
>> from the code and visible to the user. Traditionally two 7-segment displays
>> were made available on the motherboard to show the last post code that was
>> emitted. This allows diagnosis of a boot problem since it is possible to
>> see where the code got to before it died.
>>
>> On modern hardware these codes are not normally visible. On Chromebooks
>> they are displayed by the Embedded Controller (EC), so it is useful to emit
>> them. We must enable this feature for the EC to see the codes, so add an
>> option for this.
>>
>> Signed-off-by: Simon Glass <sjg at chromium.org>
>> ---
>>
>>  arch/x86/cpu/coreboot/coreboot.c     |  3 ++-
>>  arch/x86/cpu/start.S                 | 25 +++++++++++++++++++++++++
>>  arch/x86/include/asm/post.h          | 32 ++++++++++++++++++++++++++++++++
>>  board/google/chromebook_link/Kconfig |  4 ++++
>>  4 files changed, 63 insertions(+), 1 deletion(-)
>>  create mode 100644 arch/x86/include/asm/post.h
>>
>> diff --git a/arch/x86/cpu/coreboot/coreboot.c b/arch/x86/cpu/coreboot/coreboot.c
>> index 257faa1..cc7398f 100644
>> --- a/arch/x86/cpu/coreboot/coreboot.c
>> +++ b/arch/x86/cpu/coreboot/coreboot.c
>> @@ -15,6 +15,7 @@
>>  #include <asm/cache.h>
>>  #include <asm/cpu.h>
>>  #include <asm/io.h>
>> +#include <asm/post.h>
>>  #include <asm/arch-coreboot/tables.h>
>>  #include <asm/arch-coreboot/sysinfo.h>
>>  #include <asm/arch/timestamp.h>
>> @@ -68,7 +69,7 @@ void show_boot_progress(int val)
>>                 gd->arch.tsc_prev = now;
>>         }
>>  #endif
>> -       outb(val, 0x80);
>> +       outb(val, POST_PORT);
>>  }
>>
>>  int last_stage_init(void)
>> diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S
>> index 7f41475..f62ffeb 100644
>> --- a/arch/x86/cpu/start.S
>> +++ b/arch/x86/cpu/start.S
>> @@ -13,6 +13,7 @@
>>  #include <config.h>
>>  #include <version.h>
>>  #include <asm/global_data.h>
>> +#include <asm/post.h>
>>  #include <asm/processor.h>
>>  #include <asm/processor-flags.h>
>>  #include <generated/generic-asm-offsets.h>
>> @@ -60,6 +61,28 @@ _start:
>>         movw    %ax, %es
>>         movw    %ax, %ss
>>
>> +       /* Enable post codes to EC */
>> +#ifdef CONFIG_EARLY_POST_CROS_EC
>> +       mov    $0x1b, %ecx
>> +       rdmsr
>> +       and    $0x100, %eax
>> +       test   %eax, %eax
>> +       je     2f
>> +
>> +       mov    $0x8000f8f0, %eax
>> +       mov    $0xcf8, %dx
>> +       out    %eax, (%dx)
>> +       mov    $0xfed1c001, %eax
>> +       mov    $0xcfc, %dx
>> +       out    %eax, (%dx)
>> +       mov    $0xfed1f410, %esp
>> +       mov    (%esp), %eax
>> +       and    $0xfffffffb, %eax
>> +       mov    %eax, (%esp)
>> +2:
>> +#endif
>
> IMHO the early_board_init() removal should be rolled back, and the
> enable post codes is better to put there.

Yes I was thinking about that, I'll make that change.

>
>> +       post_code(POST_START)
>> +
>>         /* Clear the interrupt vectors */
>>         lidt    blank_idt_ptr
>>
>> @@ -91,6 +114,7 @@ car_init_ret:
>>
>>         /* Align global data to 16-byte boundary */
>>         andl    $0xfffffff0, %esp
>> +       post_code(POST_START_STACK)
>>
>>         /* Zero the global data since it won't happen later */
>>         xorl    %eax, %eax
>> @@ -126,6 +150,7 @@ car_init_ret:
>>         call    setup_gdt
>>
>>         /* Set parameter to board_init_f() to boot flags */
>> +       post_code(POST_START_DONE)
>>         xorl    %eax, %eax
>>
>>         /* Enter, U-boot! */
>> diff --git a/arch/x86/include/asm/post.h b/arch/x86/include/asm/post.h
>> new file mode 100644
>> index 0000000..3371185
>> --- /dev/null
>> +++ b/arch/x86/include/asm/post.h
>> @@ -0,0 +1,32 @@
>> +/*
>> + * Copyright (c) 2014 Google, Inc
>> + *
>> + * SPDX-License-Identifier:    GPL-2.0+
>> + */
>> +
>> +#ifndef _post_h
>> +#define _post_h
>> +
>> +/* port to use for post codes */
>> +#define POST_PORT              0x80
>> +
>> +/* post codes which represent various stages of init */
>> +#define POST_START             0x1e
>> +#define POST_CAR_START         0x1f
>> +
>> +#define POST_START_STACK       0x29
>> +#define POST_START_DONE                0x2a
>
> Do we follow some specification about post codes values, or are them
> just some random numbers?

Just random - they're all in one place so we can change them pretty easily.

>
>> +/* Output a post code using al - value must be 0 to 0xff */
>> +#ifdef __ASSEMBLY__
>> +#define post_code(value) \
>> +       movb    $value, %al; \
>> +       outb    %al, $POST_PORT
>> +#else
>> +static inline void post_code(int code)
>> +{
>> +       outb(code, POST_PORT);
>> +}
>> +#endif
>> +
>> +#endif
>> diff --git a/board/google/chromebook_link/Kconfig b/board/google/chromebook_link/Kconfig
>> index 975d557..9c715ba 100644
>> --- a/board/google/chromebook_link/Kconfig
>> +++ b/board/google/chromebook_link/Kconfig
>> @@ -12,4 +12,8 @@ config SYS_SOC
>>  config SYS_CONFIG_NAME
>>         default "chromebook_link"
>>
>> +config EARLY_POST_CROS_EC
>> +       bool "Enable early post to Chrome OS EC"
>> +       default y
>> +
>>  endif
>> --
>
> Regards,
> Bin

Regards,
Simon