[U-Boot] [PATCH] ARM: socfpga: Put stack at the end of SRAM

[Simon Goldschmidt <sgoldschmidt@de.pepperl-fuchs.com>]

On 14.05.2018 22:43, Marek Vasut wrote:
> On 05/14/2018 09:43 PM, Simon Goldschmidt wrote:
>>
>>
>> On 14.05.2018 17:51, Stefan Roese wrote:
>>> On 14.05.2018 11:06, Marek Vasut wrote:
>>>> On 05/14/2018 11:01 AM, Simon Goldschmidt wrote:
>>>>>
>>>>>
>>>>> On 14.05.2018 10:17, Marek Vasut wrote:
>>>>>> On 05/14/2018 10:03 AM, Simon Goldschmidt wrote:
>>>>>>> On 12.05.2018 22:27, Marek Vasut wrote:
>>>>>>>> The global data are in the .data section, so there's no point in
>>>>>>>> reserving any space for it above stack. Put stack at the end of
>>>>>>>> SRAM.
>>>>>>>>
>>>>>>>> Signed-off-by: Marek Vasut <marex@denx.de>
>>>>>>>> Cc: Chin Liang See <chin.liang.see@intel.com>
>>>>>>>> Cc: Dinh Nguyen <dinguyen@kernel.org>
>>>>>>>> ---
>>>>>>>>      include/configs/socfpga_common.h | 4 +---
>>>>>>>>      1 file changed, 1 insertion(+), 3 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/include/configs/socfpga_common.h
>>>>>>>> b/include/configs/socfpga_common.h
>>>>>>>> index 4de2aa7929..cb67d539b1 100644
>>>>>>>> --- a/include/configs/socfpga_common.h
>>>>>>>> +++ b/include/configs/socfpga_common.h
>>>>>>>> @@ -35,10 +35,8 @@
>>>>>>>>      #define CONFIG_SYS_INIT_RAM_ADDR    0xFFE00000
>>>>>>>>      #define CONFIG_SYS_INIT_RAM_SIZE    0x40000 /* 256KB */
>>>>>>>>      #endif
>>>>>>>> -#define CONFIG_SYS_INIT_SP_OFFSET        \
>>>>>>>> -    (CONFIG_SYS_INIT_RAM_SIZE - GENERATED_GBL_DATA_SIZE)
>>>>>>>>      #define CONFIG_SYS_INIT_SP_ADDR            \
>>>>>>>> -    (CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_INIT_SP_OFFSET)
>>>>>>>> +    (CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_INIT_RAM_SIZE)
>>>>>>>
>>>>>>> I think this interferes with the bootcount being stored at the end of
>>>>>>> SRAM. See the defconfigs of 'is1' and 'sr1500' boards - or my local
>>>>>>> defconfig here :-)
>>>>>>>
>>>>>>> I'd really like to keep some room here for bootcounter and some
>>>>>>> related
>>>>>>> things I store here.
>>>>>>
>>>>>> So if I understand it correctly, before this patch, the boards
>>>>>> overwrote
>>>>>> the global data ?
>>>>>
>>>>> Ehrm, reading up on the init code path in the S and C files, it seems
>>>>> like that, yes. I just used the two boards as an example. Are they
>>>>> actively maintained? get_maintainer.pl shows the boards are maintained
>>>>> by denx, so maybe you could clarify this?
>>>>
>>>> +CC Stefan.
>>>
>>> Thanks. At the time I added the bootcounter support on this platform,
>>> it used to work. I might have missed something though. Right now,
>>> I don't have access to such a platform, so its hard for me to test
>>> something. If you have some patches to fix any potential overlapping
>>> memory usages, I'll gladly review them.
>>
>> I just checked out ae996c80 and from what I can tell, the RAM layout was
>> the same at that time: include/generated/generated-asm-offsets.h contains:
>> - #define GENERATED_GBL_DATA_SIZE 208
>> - #define GD_SIZE 200
>>
>> That leaves us with an 8 byte alignment gap at the end of the SRAM and
>> that's where the boot counter is located. So the global data is not
>> overwritten, but this is more or less by chance, any change to the
>> struct definition might change this.
>>
>> Looking at just another example: the x600 board defines its SRAM_SIZE 8
>> bytes smaller than what it really is. That seems like a good idea for
>> socfpga, too. I'll see if I can provide a patch.
> 
> This looks like a hack and a bogus one. Lying about RAM size is never a
> good idea.
> 
>> Slightly off-topic: I have a constellation where the boot-counter is not
>> reset although the power has been pulled. This device has big capacitors
>> and the SRAM content seems to survive although the processor is reset.
>> To me it seems as if looking at the boot reason might be safer than
>> checking for a magic word... Any ideas?
> 
> What boot reason options do you get ?

The reset manager has a status register [1] that has various bits for 
different reasons of warm or cold reset. I'm just not sure if it's worth 
going through the hassle or if I'm alone with that problem of the 
bootcounter surviving a pull-and-replug.

[1] https://www.altera.com/hps/cyclone-v/topic/sfo1410067763568.html

Simon