diff mbox series

[PATCHv3,03/11] videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag

Message ID 20200226111529.180197-4-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. 26, 2020, 11:15 a.m. UTC 
By setting or clearing V4L2_FLAG_MEMORY_NON_CONSISTENT flag
user-space should be able to set or clear queue's NON_CONSISTENT
->dma_attrs. Queue's ->dma_attrs are passed to the underlying
allocator in __vb2_buf_mem_alloc(), so thus user-space is able
to request vb2 buffer's memory to be either consistent (coherent)
or non-consistent.

The patch set also adds a corresponding capability flag:
fill_buf_caps() reports V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS when
queue supports user-space cache management hints.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 Documentation/media/uapi/v4l/buffer.rst       | 29 +++++++++++++++++++
 .../media/uapi/v4l/vidioc-reqbufs.rst         |  7 +++++
 .../media/common/videobuf2/videobuf2-v4l2.c   |  2 ++
 include/uapi/linux/videodev2.h                |  3 ++
 4 files changed, 41 insertions(+)

Comments

Hans Verkuil Feb. 27, 2020, 12:25 p.m. UTC | #1 
On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> By setting or clearing V4L2_FLAG_MEMORY_NON_CONSISTENT flag
> user-space should be able to set or clear queue's NON_CONSISTENT
> ->dma_attrs. Queue's ->dma_attrs are passed to the underlying
> allocator in __vb2_buf_mem_alloc(), so thus user-space is able
> to request vb2 buffer's memory to be either consistent (coherent)
> or non-consistent.
> 
> The patch set also adds a corresponding capability flag:
> fill_buf_caps() reports V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS when
> queue supports user-space cache management hints.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  Documentation/media/uapi/v4l/buffer.rst       | 29 +++++++++++++++++++
>  .../media/uapi/v4l/vidioc-reqbufs.rst         |  7 +++++
>  .../media/common/videobuf2/videobuf2-v4l2.c   |  2 ++
>  include/uapi/linux/videodev2.h                |  3 ++
>  4 files changed, 41 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
> index 3112300c2fa0..6b629ac59bf2 100644
> --- a/Documentation/media/uapi/v4l/buffer.rst
> +++ b/Documentation/media/uapi/v4l/buffer.rst
> @@ -681,6 +681,35 @@ Buffer Flags
>  
>      \normalsize
>  
> +.. _memory-flags:
> +
> +Memory Consistency Flags
> +========================
> +
> +.. tabularcolumns:: |p{7.0cm}|p{2.2cm}|p{8.3cm}|
> +
> +.. cssclass:: longtable
> +
> +.. flat-table::
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths:       3 1 4
> +
> +    * .. _`V4L2_FLAG_MEMORY_NON_CONSISTENT`:
> +
> +      - ``V4L2_FLAG_MEMORY_NON_CONSISTENT``
> +      - 0x00000001
> +      - vb2 buffer is allocated either in consistent (it will be automatically

vb2 -> A

(vb2 is a kAPI term, and shouldn't be used in uAPI documentation)

> +	coherent between CPU and bus) or non-consistent memory. The latter

CPU and bus -> the CPU and the bus

> +	can provide performance gains, for instance CPU cache sync/flush

CPU -> the CPU

> +	operations can be avoided if the buffer is accessed by the corresponding
> +	device only and CPU does not read/write to/from that buffer. However,

CPU -> the CPU

> +	this requires extra care from the driver -- it must guarantee memory
> +	consistency by issuing cache flush/sync when consistency is needed.

cache -> a cache

> +	If this flag is set V4L2 will attempt to allocate vb2 buffer in

vb2 -> the

> +	non-consistent memory. The flag takes effect only if the buffer is
> +	used for :ref:`memory mapping <mmap>` I/O and the queue reports

reports -> reports the

> +	:ref:`V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS` capability.
>  
>  .. c:type:: v4l2_memory
>  
> diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> index d0c643db477a..917df6fb6486 100644
> --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> @@ -156,6 +156,13 @@ aborting or finishing any DMA in progress, an implicit
>        - Only valid for stateless decoders. If set, then userspace can set the
>          ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
>  	capture buffer until the OUTPUT timestamp changes.
> +    * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS``
> +      - 0x00000040
> +      - Set when the queue/buffer support memory consistency and cache

support -> supports

> +        management hints. See :ref:`V4L2_FLAG_MEMORY_NON_CONSISTENT`,
> +        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE` and
> +        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN`.
> +
>  
>  Return Value
>  ============
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 2a604bd7793a..f91cba37e223 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -711,6 +711,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
>  	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
> +	if ((q->allow_cache_hints != 0) && (q->io_modes & VB2_MMAP))

Just say:

	if (q->allow_cache_hints && (q->io_modes & VB2_MMAP))

Regards,

	Hans

> +		*caps |= V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS;
>  #ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
>  	if (q->supports_requests)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 5f9357dcb060..e92c29864730 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -189,6 +189,8 @@ enum v4l2_memory {
>  	V4L2_MEMORY_DMABUF           = 4,
>  };
>  
> +#define V4L2_FLAG_MEMORY_NON_CONSISTENT		(1 << 0)
> +
>  /* see also http://vektor.theorem.ca/graphics/ycbcr/ */
>  enum v4l2_colorspace {
>  	/*
> @@ -946,6 +948,7 @@ struct v4l2_requestbuffers {
>  #define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)
>  #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
> +#define V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS		(1 << 6)
>  
>  /**
>   * struct v4l2_plane - plane info for multi-planar buffers
>
Sergey Senozhatsky Feb. 28, 2020, 1:39 a.m. UTC | #2 
On (20/02/27 13:25), Hans Verkuil wrote:
[..]
> > +      - vb2 buffer is allocated either in consistent (it will be automatically
> 
> vb2 -> A
> 
> (vb2 is a kAPI term, and shouldn't be used in uAPI documentation)
> 
> > +	coherent between CPU and bus) or non-consistent memory. The latter
> 
> CPU and bus -> the CPU and the bus
> 
> > +	can provide performance gains, for instance CPU cache sync/flush
> 
> CPU -> the CPU
> 
> > +	operations can be avoided if the buffer is accessed by the corresponding
> > +	device only and CPU does not read/write to/from that buffer. However,
> 
> CPU -> the CPU
> 
> > +	this requires extra care from the driver -- it must guarantee memory
> > +	consistency by issuing cache flush/sync when consistency is needed.
> 
> cache -> a cache
> 
> > +	If this flag is set V4L2 will attempt to allocate vb2 buffer in
> 
> vb2 -> the
> 
> > +	non-consistent memory. The flag takes effect only if the buffer is
> > +	used for :ref:`memory mapping <mmap>` I/O and the queue reports
> 
> reports -> reports the

OK.

> > +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> > @@ -156,6 +156,13 @@ aborting or finishing any DMA in progress, an implicit
> >        - Only valid for stateless decoders. If set, then userspace can set the
> >          ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
> >  	capture buffer until the OUTPUT timestamp changes.
> > +    * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS``
> > +      - 0x00000040
> > +      - Set when the queue/buffer support memory consistency and cache
> 
> support -> supports

OK.

> > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > @@ -711,6 +711,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
> >  		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
> >  	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
> >  		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
> > +	if ((q->allow_cache_hints != 0) && (q->io_modes & VB2_MMAP))
> 
> Just say:
> 
> 	if (q->allow_cache_hints && (q->io_modes & VB2_MMAP))

OK.

	-ss
diff mbox series

Patch

diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
index 3112300c2fa0..6b629ac59bf2 100644
--- a/Documentation/media/uapi/v4l/buffer.rst
+++ b/Documentation/media/uapi/v4l/buffer.rst
@@ -681,6 +681,35 @@  Buffer Flags
 
     \normalsize
 
+.. _memory-flags:
+
+Memory Consistency Flags
+========================
+
+.. tabularcolumns:: |p{7.0cm}|p{2.2cm}|p{8.3cm}|
+
+.. cssclass:: longtable
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * .. _`V4L2_FLAG_MEMORY_NON_CONSISTENT`:
+
+      - ``V4L2_FLAG_MEMORY_NON_CONSISTENT``
+      - 0x00000001
+      - vb2 buffer is allocated either in consistent (it will be automatically
+	coherent between CPU and bus) or non-consistent memory. The latter
+	can provide performance gains, for instance CPU cache sync/flush
+	operations can be avoided if the buffer is accessed by the corresponding
+	device only and CPU does not read/write to/from that buffer. However,
+	this requires extra care from the driver -- it must guarantee memory
+	consistency by issuing cache flush/sync when consistency is needed.
+	If this flag is set V4L2 will attempt to allocate vb2 buffer in
+	non-consistent memory. The flag takes effect only if the buffer is
+	used for :ref:`memory mapping <mmap>` I/O and the queue reports
+	:ref:`V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS` capability.
 
 .. c:type:: v4l2_memory
 
diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
index d0c643db477a..917df6fb6486 100644
--- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
@@ -156,6 +156,13 @@  aborting or finishing any DMA in progress, an implicit
       - Only valid for stateless decoders. If set, then userspace can set the
         ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
 	capture buffer until the OUTPUT timestamp changes.
+    * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS``
+      - 0x00000040
+      - Set when the queue/buffer support memory consistency and cache
+        management hints. See :ref:`V4L2_FLAG_MEMORY_NON_CONSISTENT`,
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE` and
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN`.
+
 
 Return Value
 ============
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 2a604bd7793a..f91cba37e223 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -711,6 +711,8 @@  static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
 	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
+	if ((q->allow_cache_hints != 0) && (q->io_modes & VB2_MMAP))
+		*caps |= V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS;
 #ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
 	if (q->supports_requests)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 5f9357dcb060..e92c29864730 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -189,6 +189,8 @@  enum v4l2_memory {
 	V4L2_MEMORY_DMABUF           = 4,
 };
 
+#define V4L2_FLAG_MEMORY_NON_CONSISTENT		(1 << 0)
+
 /* see also http://vektor.theorem.ca/graphics/ycbcr/ */
 enum v4l2_colorspace {
 	/*
@@ -946,6 +948,7 @@  struct v4l2_requestbuffers {
 #define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)
 #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
 #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
+#define V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS		(1 << 6)
 
 /**
  * struct v4l2_plane - plane info for multi-planar buffers