[Mesa-dev] [PATCH] gallium/radeon: add a debug flag not to use write combining

[Marek Olšák]

On a related note, can we disable HDP flushes and other flushes for
USWC when we don't use write
combining and CPU writes to VRAM? Maybe by adding a per-IB flag that
would instruct the
kernel to flush or not flush HDP?

Marek

On Wed, Aug 5, 2015 at 4:18 AM, Michel Dänzer <michel at daenzer.net> wrote:
> On 03.08.2015 21:36, Marek Olšák wrote:
>> From: Marek Olšák <marek.olsak at amd.com>
>>
>> ---
>>  src/gallium/drivers/radeon/r600_buffer_common.c | 6 ++++--
>>  src/gallium/drivers/radeon/r600_pipe_common.c   | 1 +
>>  src/gallium/drivers/radeon/r600_pipe_common.h   | 1 +
>>  3 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeon/r600_buffer_common.c b/src/gallium/drivers/radeon/r600_buffer_common.c
>> index fc5f6c2..d5ee188 100644
>> --- a/src/gallium/drivers/radeon/r600_buffer_common.c
>> +++ b/src/gallium/drivers/radeon/r600_buffer_common.c
>> @@ -111,7 +111,8 @@ bool r600_init_resource(struct r600_common_screen *rscreen,
>>
>>       switch (res->b.b.usage) {
>>       case PIPE_USAGE_STREAM:
>> -             flags = RADEON_FLAG_GTT_WC;
>> +             if (!(rscreen->debug_flags & DBG_NO_WC))
>> +                     flags = RADEON_FLAG_GTT_WC;
>>               /* fall through */
>>       case PIPE_USAGE_STAGING:
>>               /* Transfers are likely to occur more often with these resources. */
>> @@ -133,7 +134,8 @@ bool r600_init_resource(struct r600_common_screen *rscreen,
>>       default:
>>               /* Not listing GTT here improves performance in some apps. */
>>               res->domains = RADEON_DOMAIN_VRAM;
>> -             flags |= RADEON_FLAG_GTT_WC;
>> +             if (!(rscreen->debug_flags & DBG_NO_WC))
>> +                     flags |= RADEON_FLAG_GTT_WC;
>>               break;
>>       }
>
> I think it would be both simpler and safer to mask out
> RADEON_FLAG_GTT_WC after all the code which sets the various flags.
>
>
> --
> Earthling Michel Dänzer               |               http://www.amd.com
> Libre software enthusiast             |             Mesa and X developer