[PATCHv3,03/11] videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag
Commit Message
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
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
>
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
@@ -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
@@ -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
============
@@ -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;
@@ -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