Re: [PATCH v6 03/14] videobuf2: handle V4L2 buffer cache flags

[Hans Verkuil]

On 02/06/2020 14:22, Tomasz Figa wrote:
> Hi Hans,
> 
> On Tue, Jun 2, 2020 at 11:51 AM Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
>>
>> Hi Sergey,
>>
>> While doing final testing for this patch series (together with the v4l-utils patch)
>> I found one remaining issue:
>>
>> On 14/05/2020 18:01, Sergey Senozhatsky wrote:
>>> From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
>>>
>>> Set video buffer cache management flags corresponding to V4L2 cache
>>> flags.
>>>
>>> Both ->prepare() and ->finish() cache management hints should be
>>> passed during this stage (buffer preparation), because there is
>>> no other way for user-space to tell V4L2 to avoid ->finish() cache
>>> flush.
>>>
>>> Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
>>> ---
>>>  .../media/common/videobuf2/videobuf2-v4l2.c   | 48 +++++++++++++++++++
>>>  include/media/videobuf2-core.h                | 11 +++++
>>>  2 files changed, 59 insertions(+)
>>>
>>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> index eb5d5db96552..f13851212cc8 100644
>>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> @@ -337,6 +337,53 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
>>>       return 0;
>>>  }
>>>
>>> +static void set_buffer_cache_hints(struct vb2_queue *q,
>>> +                                struct vb2_buffer *vb,
>>> +                                struct v4l2_buffer *b)
>>> +{
>>> +     /*
>>> +      * DMA exporter should take care of cache syncs, so we can avoid
>>> +      * explicit ->prepare()/->finish() syncs. For other ->memory types
>>> +      * we always need ->prepare() or/and ->finish() cache sync.
>>> +      */
>>> +     if (q->memory == VB2_MEMORY_DMABUF) {
>>> +             vb->need_cache_sync_on_finish = 0;
>>> +             vb->need_cache_sync_on_prepare = 0;
>>> +             return;
>>> +     }
>>> +
>>> +     /*
>>> +      * Cache sync/invalidation flags are set by default in order to
>>> +      * preserve existing behaviour for old apps/drivers.
>>> +      */
>>> +     vb->need_cache_sync_on_prepare = 1;
>>> +     vb->need_cache_sync_on_finish = 1;
>>> +
>>> +     if (!vb2_queue_allows_cache_hints(q)) {
>>> +             /*
>>> +              * Clear buffer cache flags if queue does not support user
>>> +              * space hints. That's to indicate to userspace that these
>>> +              * flags won't work.
>>> +              */
>>> +             b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_INVALIDATE;
>>> +             b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_CLEAN;
>>> +             return;
>>> +     }
>>
>> These two flags need to be cleared for VB2_MEMORY_DMABUF as well in the test above.
>> This bug is causing v4l2-compliance failures (use the test-media script in contrib/test
>> in v4l-utils: 'sudo test-media vim2m').
> 
> Would you be able to paste the failures, so that we know that we
> reproduce the same problems? Thanks!

For vim2m (but looks the same for vivid/vimc/vicodec):

Streaming ioctls:
        test read/write: OK (Not Supported)
        test blocking wait: OK
        Video Capture: Captured 8 buffers
        test MMAP (no poll): OK
        Video Capture: Captured 8 buffers
        test MMAP (select): OK
        Video Capture: Captured 8 buffers
        test MMAP (epoll): OK
        Video Capture: Captured 8 buffers
        test USERPTR (no poll): OK
        Video Capture: Captured 8 buffers
        test USERPTR (select): OK
                fail: v4l2-test-buffers.cpp(1874): flags & V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
                fail: v4l2-test-buffers.cpp(1937): setupDmaBuf(expbuf_node, node, q, exp_q)
        test DMABUF (no poll): FAIL
                fail: v4l2-test-buffers.cpp(1874): flags & V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
                fail: v4l2-test-buffers.cpp(1937): setupDmaBuf(expbuf_node, node, q, exp_q)
        test DMABUF (select): FAIL

Regards,

	Hans


> 
> Best regards,
> Tomasz
> 
>>
>> It's enough to post a v6.1 for this patch, everything else is fine.
>>
>> Regards,
>>
>>         Hans
>>
>>> +
>>> +     /*
>>> +      * ->finish() cache sync can be avoided when queue direction is
>>> +      * TO_DEVICE.
>>> +      */
>>> +     if (q->dma_dir == DMA_TO_DEVICE)
>>> +             vb->need_cache_sync_on_finish = 0;
>>> +
>>> +     if (b->flags & V4L2_BUF_FLAG_NO_CACHE_INVALIDATE)
>>> +             vb->need_cache_sync_on_finish = 0;
>>> +
>>> +     if (b->flags & V4L2_BUF_FLAG_NO_CACHE_CLEAN)
>>> +             vb->need_cache_sync_on_prepare = 0;
>>> +}
>>> +
>>>  static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
>>>                                   struct v4l2_buffer *b, bool is_prepare,
>>>                                   struct media_request **p_req)
>>> @@ -381,6 +428,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>>>       }
>>>
>>>       if (!vb->prepared) {
>>> +             set_buffer_cache_hints(q, vb, b);
>>>               /* Copy relevant information provided by the userspace */
>>>               memset(vbuf->planes, 0,
>>>                      sizeof(vbuf->planes[0]) * vb->num_planes);
>>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>>> index 7f39d9fffc8c..ccc5c498d3e3 100644
>>> --- a/include/media/videobuf2-core.h
>>> +++ b/include/media/videobuf2-core.h
>>> @@ -635,6 +635,17 @@ struct vb2_queue {
>>>  #endif
>>>  };
>>>
>>> +/**
>>> + * vb2_queue_allows_cache_hints() - Return true if the queue allows cache
>>> + * and memory consistency hints.
>>> + *
>>> + * @q:               pointer to &struct vb2_queue with videobuf2 queue
>>> + */
>>> +static inline bool vb2_queue_allows_cache_hints(struct vb2_queue *q)
>>> +{
>>> +     return q->allow_cache_hints && q->memory == VB2_MEMORY_MMAP;
>>> +}
>>> +
>>>  /**
>>>   * vb2_plane_vaddr() - Return a kernel virtual address of a given plane.
>>>   * @vb:              pointer to &struct vb2_buffer to which the plane in
>>>
>>