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

[Bin Meng]

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.

> +       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?

> +/* 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