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

[chenhc at lemote.com]

> On Mon, 2012-02-27 at 10:44 +0800, Chen Jie wrote:
>> Hi,
>>
>> For this occasional GPU lockup when returns from STR/STD, I find
>> followings(when the problem happens):
>>
>> The value of SRBM_STATUS is whether 0x20002040 or 0x20003040.
>> Which means:
>> * HI_RQ_PENDING(There is a HI/BIF request pending in the SRBM)
>> * MCDW_BUSY(Memory Controller Block is Busy)
>> * BIF_BUSY(Bus Interface is Busy)
>> * MCDX_BUSY(Memory Controller Block is Busy) if is 0x20003040
>> Are MCDW_BUSY and MCDX_BUSY two memory channels? What is the
>> relationship among GART mapped memory, On-board video memory and MCDX,
>> MCDW?
>>
>> CP_STAT: the CSF_RING_BUSY is always set.
>
> Once the memory controller fails to do a pci transaction the CP
> will be stuck. At least if ring is in system memory, if ring is
> in vram CP might be stuck too because anyway everything goes
> through the MC.
>
I've tried the method of rs600 for gpu reset (use rs600_bm_disable() to
disable PCI MASTER bit and enable it after reset), but it doesn't solve
the problem. Then I found that in r100_bm_disable() it do more things,
e.g. writing the GPU register R_000030_BUS_CNTL. In r600_reg.h there is
a register R600_BUS_CNTL, does this register have a similar function?
 But I don't know how to use it...

Huacai Chen

>>
>> There are many CP_PACKET2(0x80000000) in CP ring(more than three
>> hundreds). e.g.
>> r[131800]=0x00028000
>> r[131801]=0xc0016800
>> r[131802]=0x00000140
>> r[131803]=0x000079c5
>> r[131804]=0x0000304a
>> r[131805] ... r[132143]=0x80000000
>> r[132144]=0xffff0000
>> After the first reset, GPU will lockup again, this time, typically
>> there are 320 dwords in CP ring -- with 319 CP_PACKET2 and 0xc0033d00
>> in the end.
>> Are these normal?
>>
>> BTW, is there any way for X to switch to NOACCEL mode when the problem
>> happens? Thus users will have a chance to save their documents and
>> then reboot machine.
>
> I have been meaning to patch the ddx to fallback to sw after GPU lockup.
> But this is useless in today world, where everything is composited ie
> the screen is updated using the 3D driver for which there is no easy
> way to suddenly migrate to  software rendering. I will still probably
> do the ddx patch at one point.
>
> Cheers,
> Jerome
>
>