[U-Boot] [PATCH 03/10] x86: Permit bootstage and timer data to be used prior to relocation

[Graeme Russ]

Hi Simon,

On Wed, Dec 19, 2012 at 12:32 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi Graeme,
>
> On Fri, Dec 14, 2012 at 2:35 PM, Simon Glass <sjg at chromium.org> wrote:
>>
>> Hi Graeme,
>>
>>
>> On Fri, Dec 14, 2012 at 2:15 PM, Graeme Russ <graeme.russ at gmail.com>
>> wrote:
>> > Hi Simon,
>> >
>> > On 15/12/12 08:13, Simon Glass wrote:
>> >> It is useful to be able to access the timer before U-Boot has relocated
>> >> so that we can fully support bootstage.
>> >>
>> >> Move the relevant variables to the data region to support this.
>> >>
>> >> Signed-off-by: Simon Glass <sjg at chromium.org>
>> >> ---
>> >>  arch/x86/cpu/coreboot/coreboot.c |    4 ++--
>> >>  arch/x86/cpu/interrupts.c        |    2 +-
>> >>  arch/x86/lib/timer.c             |    2 +-
>> >>  3 files changed, 4 insertions(+), 4 deletions(-)
>> >>
>> >> diff --git a/arch/x86/cpu/coreboot/coreboot.c
>> >> b/arch/x86/cpu/coreboot/coreboot.c
>> >> index 9c9431e..22474f5 100644
>> >> --- a/arch/x86/cpu/coreboot/coreboot.c
>> >> +++ b/arch/x86/cpu/coreboot/coreboot.c
>> >> @@ -68,8 +68,8 @@ int board_early_init_r(void)
>> >>  void show_boot_progress(int val)
>> >>  {
>> >>  #if MIN_PORT80_KCLOCKS_DELAY
>> >> -     static uint32_t prev_stamp;
>> >> -     static uint32_t base;
>> >> +     static uint32_t prev_stamp __attribute__((section(".data")));
>> >> +     static uint32_t base __attribute__((section(".data")));
>> >
>> > NAK
>> >
>> > This may work for coreboot where SDRAM is already initialised and you've
>> > loaded U-Boot into RAM, but it will not work when U-Boot is in Flash as
>> > all
>> > sections (including .data) are read-only until after relocation.
>> >
>> > The stack and Global Data are the only guaranteed read/write locations
>> > prior to relocation
>>
>> Ah yes, I was thinking of your comment that all boards would move to
>> use coreboot. If that is not the case, then I will need to add
>> something to global data for the timer. And I don't want to do that
>> while generic board is in progress since it creates conflicts.

I'm trying to remember the context of my comment regarding only having
coreboot boards. But anyway, not having any writeable data prior to
relocation (other than the stack and gd) is a fundamental principle
that we cannot simply avoid (although I must admit I don't know what
the go is with SPL and U-Boot relocation).

> Any thoughts on this point, please? I presume at least I can use RAM once
> dram_init() is called. But when running from coreboot the RAM is already set
> up...

You will need to use global data to store the static variables. That's
what the other arches do

Regards,

Graeme