We need to always set ->need_cache_sync_on_prepare and
->need_cache_sync_on_finish when we initialize vb2 buffer.
Currently these flags are set/adjusted only in V4L2's
vb2_queue_or_prepare_buf(), which means that for the code
paths that don't use V4L2 vb2 will always tell videobuf2
core to skip ->prepare() and ->finish() cache syncs/flushes.
This is a quick solution that should do the trick. The
proper fix, however, is much more complicated and requires
a rather big videobuf2 refactoring - we need to move cache
sync/flush decision making out of core videobuf2 to the
allocators.
Reported-by: Tomasz Figa <[email protected]>
Signed-off-by: Sergey Senozhatsky <[email protected]>
---
drivers/media/common/videobuf2/videobuf2-core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 5499013cf82e..14a26888a892 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -414,6 +414,8 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
vb->index = q->num_buffers + buffer;
vb->type = q->type;
vb->memory = memory;
+ vb->need_cache_sync_on_prepare = 1;
+ vb->need_cache_sync_on_finish = 1;
for (plane = 0; plane < num_planes; ++plane) {
vb->planes[plane].length = plane_sizes[plane];
vb->planes[plane].min_length = plane_sizes[plane];
--
2.29.2
On 27/11/2020 10:41, Sergey Senozhatsky wrote:
> We need to always set ->need_cache_sync_on_prepare and
> ->need_cache_sync_on_finish when we initialize vb2 buffer.
>
> Currently these flags are set/adjusted only in V4L2's
> vb2_queue_or_prepare_buf(), which means that for the code
> paths that don't use V4L2 vb2 will always tell videobuf2
> core to skip ->prepare() and ->finish() cache syncs/flushes.
>
> This is a quick solution that should do the trick. The
> proper fix, however, is much more complicated and requires
> a rather big videobuf2 refactoring - we need to move cache
> sync/flush decision making out of core videobuf2 to the
> allocators.
>
> Reported-by: Tomasz Figa <[email protected]>
> Signed-off-by: Sergey Senozhatsky <[email protected]>
> ---
> drivers/media/common/videobuf2/videobuf2-core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 5499013cf82e..14a26888a892 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -414,6 +414,8 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> vb->index = q->num_buffers + buffer;
> vb->type = q->type;
> vb->memory = memory;
> + vb->need_cache_sync_on_prepare = 1;
> + vb->need_cache_sync_on_finish = 1;
I think this needs a comment, basically explaining what you said in
the commit log. It's not obvious from the code that this is a
workaround.
Regards,
Hans
> for (plane = 0; plane < num_planes; ++plane) {
> vb->planes[plane].length = plane_sizes[plane];
> vb->planes[plane].min_length = plane_sizes[plane];
>
On (20/11/27 13:59), Hans Verkuil wrote:
>
> I think this needs a comment, basically explaining what you said in
> the commit log. It's not obvious from the code that this is a
> workaround.
Something like this?
---
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 5499013cf82e..21b2b0ae3629 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -414,6 +414,16 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
vb->index = q->num_buffers + buffer;
vb->type = q->type;
vb->memory = memory;
+ /*
+ * A workaround fix. We need to set these flags here so that
+ * videobuf2 core will always call ->prepare()/->finish()
+ * cache sync/flush on vb2 buffers. Otherwise, for backends
+ * that don't rely on V4L2 (perhaps dvb) these flags will
+ * always be false and, hence, videobuf2 core will skip cache
+ * sync/flush operations.
+ */
+ vb->need_cache_sync_on_prepare = 1;
+ vb->need_cache_sync_on_finish = 1;
for (plane = 0; plane < num_planes; ++plane) {
vb->planes[plane].length = plane_sizes[plane];
vb->planes[plane].min_length = plane_sizes[plane];
On 27/11/2020 15:30, Sergey Senozhatsky wrote:
> On (20/11/27 13:59), Hans Verkuil wrote:
>>
>> I think this needs a comment, basically explaining what you said in
>> the commit log. It's not obvious from the code that this is a
>> workaround.
>
> Something like this?
Yes.
BTW, wouldn't it be sufficient to change this code to:
if (!q->allow_cache_hints && q->memory != VB2_MEMORY_DMABUF) {
vb->need_cache_sync_on_prepare = 1;
vb->need_cache_sync_on_finish = 1;
}
Or am I missing something?
DVB drivers do not set this flag, and even for DVB cache sync shouldn't be
needed for DMABUF, right?
Regards,
Hans
>
> ---
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 5499013cf82e..21b2b0ae3629 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -414,6 +414,16 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> vb->index = q->num_buffers + buffer;
> vb->type = q->type;
> vb->memory = memory;
> + /*
> + * A workaround fix. We need to set these flags here so that
> + * videobuf2 core will always call ->prepare()/->finish()
> + * cache sync/flush on vb2 buffers. Otherwise, for backends
> + * that don't rely on V4L2 (perhaps dvb) these flags will
> + * always be false and, hence, videobuf2 core will skip cache
> + * sync/flush operations.
> + */
> + vb->need_cache_sync_on_prepare = 1;
> + vb->need_cache_sync_on_finish = 1;
> for (plane = 0; plane < num_planes; ++plane) {
> vb->planes[plane].length = plane_sizes[plane];
> vb->planes[plane].min_length = plane_sizes[plane];
>
On (20/11/27 15:56), Hans Verkuil wrote:
> Yes.
>
> BTW, wouldn't it be sufficient to change this code to:
>
> if (!q->allow_cache_hints && q->memory != VB2_MEMORY_DMABUF) {
> vb->need_cache_sync_on_prepare = 1;
> vb->need_cache_sync_on_finish = 1;
> }
I think it would be sufficient.
-ss
On Sat, Nov 28, 2020 at 1:35 AM Sergey Senozhatsky
<[email protected]> wrote:
>
> On (20/11/27 15:56), Hans Verkuil wrote:
> > Yes.
> >
> > BTW, wouldn't it be sufficient to change this code to:
> >
> > if (!q->allow_cache_hints && q->memory != VB2_MEMORY_DMABUF) {
> > vb->need_cache_sync_on_prepare = 1;
> > vb->need_cache_sync_on_finish = 1;
> > }
>
> I think it would be sufficient.
Does it matter at this point if allow_cache_hints is set or not?
Best regards,
Tomasz
On (20/11/28 01:50), Tomasz Figa wrote:
> On Sat, Nov 28, 2020 at 1:35 AM Sergey Senozhatsky
> <[email protected]> wrote:
> >
> > On (20/11/27 15:56), Hans Verkuil wrote:
> > > Yes.
> > >
> > > BTW, wouldn't it be sufficient to change this code to:
> > >
> > > if (!q->allow_cache_hints && q->memory != VB2_MEMORY_DMABUF) {
> > > vb->need_cache_sync_on_prepare = 1;
> > > vb->need_cache_sync_on_finish = 1;
> > > }
> >
> > I think it would be sufficient.
>
> Does it matter at this point if allow_cache_hints is set or not?
That's a good question. I'd say that it'll probably make sense to set
need_cache_sync for as many buffers as possible, regardless the queue
configuration (except for ->memory type), just to stay on the safe side.
I can spin another patch version.
-ss