Re: [PATCH] drm/ttm: Set CPU caching mode to cached for BOs being swapped out

["Michel Dänzer" <michel@daenzer.net>]

On 05.11.2015 17:47, Thomas Hellstrom wrote:
> Hi, Michel,
> 
> On 11/05/2015 09:08 AM, Michel Dänzer wrote:
>> From: Michel Dänzer <michel.daenzer@amd.com>
>>
>> I ran into the BUG_ON in ttm_tt_swapout, presumably the BO being swapped
>> out was using a write-combined CPU mapping.
>>
>> Instead of BUGging out, just set the caching mode to what's needed.
>>
>> Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
>> ---
>>  drivers/gpu/drm/ttm/ttm_tt.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
>> index 4e19d0f..c2794eb 100644
>> --- a/drivers/gpu/drm/ttm/ttm_tt.c
>> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
>> @@ -334,7 +334,8 @@ int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistent_swap_storage)
>>  	int ret = -ENOMEM;
>>  
>>  	BUG_ON(ttm->state != tt_unbound && ttm->state != tt_unpopulated);
>> -	BUG_ON(ttm->caching_state != tt_cached);
>> +
>> +	ttm_tt_set_caching(ttm, tt_cached);
>>  
>>  	if (!persistent_swap_storage) {
>>  		swap_storage = shmem_file_setup("ttm swap",
> 
> This *is* actually a bug somewhere, since before ttm_tt_swapout,
> ttm_bo_swapout should have moved out the bo to system and set
> the correct caching.

Maybe ttm_bo_swapout needs to check ttm->caching_state explicitly?
AFAICT it only checks the placement flags, but we allow all caching
modes for GTT.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer
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