diff mbox series

[RFC,PATCHv2,01/12] videobuf2: add cache management members

Message ID 20200204025641.218376-2-senozhatsky@chromium.org (mailing list archive)
State New, archived
Headers show
Series Implement V4L2_BUF_FLAG_NO_CACHE_* flags | expand

Commit Message

Sergey Senozhatsky Feb. 4, 2020, 2:56 a.m. UTC
Extend vb2_buffer and vb2_queue structs with cache management
members.

V4L2 UAPI already contains two buffer flags which user-space,
supposedly, can use to control buffer cache sync:

- V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
- V4L2_BUF_FLAG_NO_CACHE_CLEAN

None of these, however, do anything at the moment. This patch
set is intended to change it.

Since user-space cache management hints are supposed to be
implemented on a per-buffer basis we need to extend vb2_buffer
struct with two new memebers ->need_cache_sync_on_prepare and
->need_cache_sync_on_finish, which will store corresponding
user-space hints.

In order to preserve the existing behaviour, user-space cache
managements flags will be handled only by those drivers that
permit user-space cache hints. That's the purpose of vb2_queue
->allow_cache_hints member. Driver must set ->allow_cache_hints
during queue initialisation to enable cache management hints
mechanism.

Only drivers that set ->allow_cache_hints during queue initialisation
will handle user-space cache management hints. Otherwise hints
will be ignored.

Change-Id: I52beec2a0d021b7a3715b4f6ae4bfd9dc5e94f0d
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 include/media/videobuf2-core.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Hans Verkuil Feb. 19, 2020, 8:05 a.m. UTC | #1
On 2/4/20 3:56 AM, Sergey Senozhatsky wrote:
> Extend vb2_buffer and vb2_queue structs with cache management
> members.
> 
> V4L2 UAPI already contains two buffer flags which user-space,
> supposedly, can use to control buffer cache sync:
> 
> - V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
> - V4L2_BUF_FLAG_NO_CACHE_CLEAN
> 
> None of these, however, do anything at the moment. This patch
> set is intended to change it.
> 
> Since user-space cache management hints are supposed to be
> implemented on a per-buffer basis we need to extend vb2_buffer
> struct with two new memebers ->need_cache_sync_on_prepare and
> ->need_cache_sync_on_finish, which will store corresponding
> user-space hints.
> 
> In order to preserve the existing behaviour, user-space cache
> managements flags will be handled only by those drivers that
> permit user-space cache hints. That's the purpose of vb2_queue
> ->allow_cache_hints member. Driver must set ->allow_cache_hints
> during queue initialisation to enable cache management hints
> mechanism.
> 
> Only drivers that set ->allow_cache_hints during queue initialisation
> will handle user-space cache management hints. Otherwise hints
> will be ignored.
> 
> Change-Id: I52beec2a0d021b7a3715b4f6ae4bfd9dc5e94f0d
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  include/media/videobuf2-core.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index a2b2208b02da..026004180440 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -263,6 +263,10 @@ struct vb2_buffer {
>  	 *			after the 'buf_finish' op is called.
>  	 * copied_timestamp:	the timestamp of this capture buffer was copied
>  	 *			from an output buffer.
> +	 * need_cache_sync_on_prepare: do not sync/invalidate cache from
> +	 * 			buffer's ->prepare() callback.
> +	 * need_cache_sync_on_finish: do not sync/invalidate cache from buffer's
> +	 * 			->finish() callback.

Shouldn't 'do not' be deleted from the flag descriptions? If the flag is set,
then you need to sync/validate, right?

Regards,

	Hans

>  	 * queued_entry:	entry on the queued buffers list, which holds
>  	 *			all buffers queued from userspace
>  	 * done_entry:		entry on the list that stores all buffers ready
> @@ -273,6 +277,8 @@ struct vb2_buffer {
>  	unsigned int		synced:1;
>  	unsigned int		prepared:1;
>  	unsigned int		copied_timestamp:1;
> +	unsigned int		need_cache_sync_on_prepare:1;
> +	unsigned int		need_cache_sync_on_finish:1;
>  
>  	struct vb2_plane	planes[VB2_MAX_PLANES];
>  	struct list_head	queued_entry;
> @@ -491,6 +497,9 @@ struct vb2_buf_ops {
>   * @uses_requests: requests are used for this queue. Set to 1 the first time
>   *		a request is queued. Set to 0 when the queue is canceled.
>   *		If this is 1, then you cannot queue buffers directly.
> + * @allow_cache_hints: when set user-space can pass cache management hints in
> + * 		order to skip cache flush/invalidation on ->prepare() or/and
> + * 		->finish().
>   * @lock:	pointer to a mutex that protects the &struct vb2_queue. The
>   *		driver can set this to a mutex to let the v4l2 core serialize
>   *		the queuing ioctls. If the driver wants to handle locking
> @@ -564,6 +573,7 @@ struct vb2_queue {
>  	unsigned			requires_requests:1;
>  	unsigned			uses_qbuf:1;
>  	unsigned			uses_requests:1;
> +	unsigned			allow_cache_hints:1;
>  
>  	struct mutex			*lock;
>  	void				*owner;
>
Sergey Senozhatsky Feb. 19, 2020, 8:16 a.m. UTC | #2
On (20/02/19 09:05), Hans Verkuil wrote:
> On 2/4/20 3:56 AM, Sergey Senozhatsky wrote:

[..]

> > diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> > index a2b2208b02da..026004180440 100644
> > --- a/include/media/videobuf2-core.h
> > +++ b/include/media/videobuf2-core.h
> > @@ -263,6 +263,10 @@ struct vb2_buffer {
> >  	 *			after the 'buf_finish' op is called.
> >  	 * copied_timestamp:	the timestamp of this capture buffer was copied
> >  	 *			from an output buffer.
> > +	 * need_cache_sync_on_prepare: do not sync/invalidate cache from
> > +	 * 			buffer's ->prepare() callback.
> > +	 * need_cache_sync_on_finish: do not sync/invalidate cache from buffer's
> > +	 * 			->finish() callback.
> 
> Shouldn't 'do not' be deleted from the flag descriptions? If the flag is set,
> then you need to sync/validate, right?

Hmm, kind of work both ways. Maybe the wording can be more specific,
e.g. "Do/skip cache sync/invalidation" even more detailed "When set
perform cache sync/invalidation from ..."

	-ss
Hans Verkuil Feb. 19, 2020, 8:27 a.m. UTC | #3
On 2/19/20 9:16 AM, Sergey Senozhatsky wrote:
> On (20/02/19 09:05), Hans Verkuil wrote:
>> On 2/4/20 3:56 AM, Sergey Senozhatsky wrote:
> 
> [..]
> 
>>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>>> index a2b2208b02da..026004180440 100644
>>> --- a/include/media/videobuf2-core.h
>>> +++ b/include/media/videobuf2-core.h
>>> @@ -263,6 +263,10 @@ struct vb2_buffer {
>>>  	 *			after the 'buf_finish' op is called.
>>>  	 * copied_timestamp:	the timestamp of this capture buffer was copied
>>>  	 *			from an output buffer.
>>> +	 * need_cache_sync_on_prepare: do not sync/invalidate cache from
>>> +	 * 			buffer's ->prepare() callback.
>>> +	 * need_cache_sync_on_finish: do not sync/invalidate cache from buffer's
>>> +	 * 			->finish() callback.
>>
>> Shouldn't 'do not' be deleted from the flag descriptions? If the flag is set,
>> then you need to sync/validate, right?
> 
> Hmm, kind of work both ways. Maybe the wording can be more specific,
> e.g. "Do/skip cache sync/invalidation" even more detailed "When set
> perform cache sync/invalidation from ..."

"When set..." works well. It's explicit.

Regards,

	Hans

> 
> 	-ss
>
diff mbox series

Patch

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index a2b2208b02da..026004180440 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -263,6 +263,10 @@  struct vb2_buffer {
 	 *			after the 'buf_finish' op is called.
 	 * copied_timestamp:	the timestamp of this capture buffer was copied
 	 *			from an output buffer.
+	 * need_cache_sync_on_prepare: do not sync/invalidate cache from
+	 * 			buffer's ->prepare() callback.
+	 * need_cache_sync_on_finish: do not sync/invalidate cache from buffer's
+	 * 			->finish() callback.
 	 * queued_entry:	entry on the queued buffers list, which holds
 	 *			all buffers queued from userspace
 	 * done_entry:		entry on the list that stores all buffers ready
@@ -273,6 +277,8 @@  struct vb2_buffer {
 	unsigned int		synced:1;
 	unsigned int		prepared:1;
 	unsigned int		copied_timestamp:1;
+	unsigned int		need_cache_sync_on_prepare:1;
+	unsigned int		need_cache_sync_on_finish:1;
 
 	struct vb2_plane	planes[VB2_MAX_PLANES];
 	struct list_head	queued_entry;
@@ -491,6 +497,9 @@  struct vb2_buf_ops {
  * @uses_requests: requests are used for this queue. Set to 1 the first time
  *		a request is queued. Set to 0 when the queue is canceled.
  *		If this is 1, then you cannot queue buffers directly.
+ * @allow_cache_hints: when set user-space can pass cache management hints in
+ * 		order to skip cache flush/invalidation on ->prepare() or/and
+ * 		->finish().
  * @lock:	pointer to a mutex that protects the &struct vb2_queue. The
  *		driver can set this to a mutex to let the v4l2 core serialize
  *		the queuing ioctls. If the driver wants to handle locking
@@ -564,6 +573,7 @@  struct vb2_queue {
 	unsigned			requires_requests:1;
 	unsigned			uses_qbuf:1;
 	unsigned			uses_requests:1;
+	unsigned			allow_cache_hints:1;
 
 	struct mutex			*lock;
 	void				*owner;