[mipsel+rs780e]Occasionally "GPU lockup" after resuming from suspend.

[Jerome Glisse]

2011/12/16  <chenhc at lemote.com>:
>> On Don, 2011-12-08 at 19:35 +0800, chenhc at lemote.com wrote:
>>>
>>> I found CP_RB_WPTR has changed when "ring test failed", so I think CP is
>>> active, but what it get from ring buffer is wrong.
>>
>> CP_RB_WPTR is normally only changed by the CPU after adding commands to
>> the ring buffer, so I'm afraid that may not be a valid conclusion.
>>
>>
> I'm sorry, I've made a spelling mistake. In fact, CP_RB_RPTR and
> CP_RB_WPTR both changed, so I think CP is active.
>
>>> Then, I want to know whether there is a way to check the content that
>>> GPU get from ring buffer.
>>
>> See the r100_debugfs_cp_csq_fifo() function, which generates the output
>> for /sys/kernel/debug/dri/0/r100_cp_csq_fifo.
>>
> Hmmm, I don't think this function can be used by r600 (or write a similar
> one for R600), because I haven't found CSQ registers in r600 code.
>
>>
>>> BTW, when I use "echo shutdown > /sys/power/disk; echo disk >
>>> /sys/power/state" to do a hibernation, there will be occasionally "GPU
>>> reset" just like suspend. However, if I use "echo reboot >
>>> /sys/power/disk; echo disk > /sys/power/state" to do a hibernation and
>>> wakeup automatically, there is no "GPU reset" after hundreds of tests.
>>> What does this imply? Power loss cause something break?
>>
>> Yeah, it sounds like the resume code doesn't properly re-initialize
>> something that's preserved on a warm boot but lost on a cold boot.
>>
>>
>> --
>> Earthling Michel D
>

It might be pci issue, you should check pci configuration before and after
suspend thought kernel should properly restore things. The cp might still
be reading random data that doesn't lockup the cp (i saw it happen more
than once).

Cheers,
Jerome