[U-Boot] [PATCH 09/14] tegra: Add warmboot implementation

[Simon Glass]

Hi Yen,

On Fri, Jan 13, 2012 at 2:04 PM, Yen Lin <yelin at nvidia.com> wrote:
> Hi Simon,
>
> On Fri, 2012-01-13 at 11:34 -0800, Simon Glass wrote:
>> Hi Stephen,
>>
>> [Yen please can you read this also?]
>>
>> On Tue, Jan 10, 2012 at 10:30 AM, Stephen Warren <swarren at nvidia.com> wrote:
>> > On 12/26/2011 12:33 PM, Simon Glass wrote:
>> >> From: Yen Lin <yelin at nvidia.com>
>> >>
>> >> Add code to set up the warm boot area in the Tegra CPU ready for a
>> >> resume after suspend.
>> >>
>> >> Signed-off-by: Simon Glass <sjg at chromium.org>
>> >
>> > How come Yen's S-o-b line is missing here?
>> >
>> > As a general comment on this patch, it contains a lot of structure
>> > definitions and defines that should really be part of the clock module's
>> > headers and similar; why not just included the clock headers and place
>> > all the definitions in those headers if they aren't already there?
>>
>> Yes this bit of it got a pretty light review at the time and I was
>> reluctant to press on the bitfields when that side of things was still
>> up in the air. No functions exist to access these things and using the
>> clk_rst.h header adds a mountain of ugly reg & OSC_FREQ_MASK) >>
>> OSC_FREQ_SHIFT to the code. I am still uncomfortable with how this
>> sort of thing is done in U-Boot.
>>
>> Also the AVP code cannot call functions in clock.c (they are in SDRAM
>> which isn't on yet), so we need the structures or some sort of access
>> there anyway.
>>
>> I will tidy up some low-hanging fruit in warmboot.c but don't know
>> that I can do much with warmboot_avp.c. At least it isn't assembler
>> anymore!
>>
>> But there a few questions here. Firstly it seems that it saves some
>> memory speed info to scratch2 but never restores it. Then it restores
>> CPU speed from scratch3 but I can't see where it saves it. Does Yen
>> have any comments on that? Apparently it works because we have been
>> using it, but... If it is saving things that are never restored I
>> could dump that and reduce the code size.
>>
>
> U-boot code saves sdram parameters to scratch2, scratch4, and scratch 24
> registers, so when system resumes, bootrom can restore sdram parameters
> from these registers.
>
> The scratch3 register content was saved by kernel before suspend, and is
> used by the warmboot code to restore PLLX settings.

Thanks for the info.

On resume I do not see it using scratch2, 4 or 24 within U-Boot. Are
those used in the kernel?

I should add something to document this so the kernel people can match
up when that side of it goes up stream.

Regards,
Simon

>
>
> Regards,
>
> Yen
>
>
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