[Mesa-dev] [PATCH] gbm/dri: Flush after unmap

[Thomas Hellstrom]

Hi, Emil,

On 03/29/2017 01:30 PM, Emil Velikov wrote:
> Hi Thomas,
>
> On 28 March 2017 at 20:39, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>> Drivers may queue dma operations on the context at unmap time so we need
>> to flush to make sure the data gets to the bo. Ideally the application
>> would take care of this, but since there appears to be no exported gbm
>> flush functionality we need to explicitly flush at unmap time.
>>
>> This fixes a problem where kmscube on vmwgfx in rgba textured mode would
>> render using an uninitialized texture rather than the intended
>> rgba pattern.
>>
> I haven't checked but the issue should not be restricted to vmwgfx, right ?
>
> Perhaps we should add the following
> Fixes: 8aeb6d768b4 ("gbm: Add map/unmap functions")
> CC: <mesa-stable at lists.freedesktop.org>

Unfortunately I've, perhaps a bit prematurely, already pushed the fix.
Is there a way to get it
into stable after push?


>
>> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
>> ---
>>  src/gbm/backends/dri/gbm_dri.c | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/gbm/backends/dri/gbm_dri.c b/src/gbm/backends/dri/gbm_dri.c
>> index ac7ede8..6c2244c 100644
>> --- a/src/gbm/backends/dri/gbm_dri.c
>> +++ b/src/gbm/backends/dri/gbm_dri.c
>> @@ -243,7 +243,7 @@ struct dri_extension_match {
>>  };
>>
>>  static struct dri_extension_match dri_core_extensions[] = {
>> -   { __DRI2_FLUSH, 1, offsetof(struct gbm_dri_device, flush) },
>> +   { __DRI2_FLUSH, 4, offsetof(struct gbm_dri_device, flush) },
> Currently the classic nouveau, radeon/r200 and i915 drivers do not
> support v4 of the extension.
> As-is this will 'break' them... if they ever worked to begin with.
>
> One solution is to bail out (return -ENOSYS or similar) in map/unmap
> API of the when the DRI module is too old.
> Just some ^^ food for thought.

Hmm. Is there even a use-case for gbm with those drivers? If so we
should perhaps make them up-to-date with the flush extension.

>
> -Emil

/Thomas