Jerome Glisse wrote:
> On Mon, 2009-04-20 at 14:50 +0200, Thomas Hellström wrote:
>   
>> Jerome Glisse wrote:
>>     
>>> On Mon, 2009-04-20 at 14:02 +0200, Jerome Glisse wrote:
>>>   
>>>       
>>>> On Mon, 2009-04-20 at 12:13 +0200, Thomas Hellstrom wrote:
>>>>     
>>>>         
>>>>> If there was an erratum causing PAT not to be enabled on your processor, 
>>>>> then definitely that
>>>>> may have cause strange inconsistencies.
>>>>>
>>>>> Thanks,
>>>>> Thomas.
>>>>>       
>>>>>           
>>>> I think ttm_tt caching stuff does follow kernel policies outlined
>>>> in Documentation/x86/pat.txt well at least from understanding of
>>>> code i have right now through (call chains being sometimes hard
>>>> to fully follow). As also have another issue it seems that calling
>>>> set_memory_(uc|wc) while suspending lockup the cpu or at least doesn't
>>>> return, is this somethings i should expect ?
>>>>
>>>> Cheers,
>>>> Jerome
>>>>
>>>>     
>>>>         
>>> Speaking about caching i think we should only call
>>> ttm_tt_set_placement_caching in mmap function as otherwise it's
>>> useless to waste time changing cache policy,
>>>   
>>>       
>> Jerome,
>> The current code should never change caching policy when it's not 
>> strictly needed.
>> If you hit such a case, it's probably a bug.
>>
>> Could you illustrate a case where you're seeing this?
>>
>> /Thomas
>>
>>     
>
> My problem is on vram eviction on suspend, vram memory is flag as WC
> so it allocate a ttm and try to set it to wc which fails badly. This
> why i was thinking of setting cache properties in mmap and not in
> validate or a path hit by bo_move.
>
>   
Ah, OK.
You could adjust this behavior in bo_driver::evict_flags.
For VRAM eviction, you can do:

return (cur_placement &~TTM_PL_MASK_CACHING) | TTM_PL_FLAG_SYSTEM | 
TTM_PL_FLAG_CACHED;

Looks like openChrome may also benefit from this...

/Thomas




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