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From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Tomasz Figa <tfiga@chromium.org>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>,
	Ricardo Ribalda <ribalda@chromium.org>,
	Christoph Hellwig <hch@lst.de>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: [PATCHv4 5/8] videobuf2: add V4L2_MEMORY_FLAG_NON_COHERENT flag
Date: Tue, 27 Jul 2021 16:05:14 +0900	[thread overview]
Message-ID: <20210727070517.443167-6-senozhatsky@chromium.org> (raw)
In-Reply-To: <20210727070517.443167-1-senozhatsky@chromium.org>

By setting or clearing V4L2_MEMORY_FLAG_NON_COHERENT flag
user-space should be able to hint vb2 that either a non-coherent
(if supported) or coherent memory should be used for the buffer
allocation.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 .../userspace-api/media/v4l/buffer.rst        | 40 ++++++++++++++++++-
 .../media/v4l/vidioc-reqbufs.rst              |  5 ++-
 include/uapi/linux/videodev2.h                |  2 +
 3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst
index e991ba73d873..4638ec64db00 100644
--- a/Documentation/userspace-api/media/v4l/buffer.rst
+++ b/Documentation/userspace-api/media/v4l/buffer.rst
@@ -676,8 +676,6 @@ Buffer Flags
 
     \normalsize
 
-.. _memory-flags:
-
 enum v4l2_memory
 ================
 
@@ -701,6 +699,44 @@ enum v4l2_memory
       - 4
       - The buffer is used for :ref:`DMA shared buffer <dmabuf>` I/O.
 
+.. _memory-flags:
+
+Memory Consistency Flags
+------------------------
+
+.. raw:: latex
+
+    \small
+
+.. tabularcolumns:: |p{7.0cm}|p{2.1cm}|p{8.4cm}|
+
+.. cssclass:: longtable
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * .. _`V4L2-MEMORY-FLAG-NON-COHERENT`:
+
+      - ``V4L2_MEMORY_FLAG_NON_COHERENT``
+      - 0x00000001
+      - A buffer is allocated either in coherent (it will be automatically
+	coherent between the CPU and the bus) or non-coherent memory. The
+	latter can provide performance gains, for instance the CPU cache
+	sync/flush operations can be avoided if the buffer is accessed by the
+	corresponding device only and the CPU does not read/write to/from that
+	buffer. However, this requires extra care from the driver -- it must
+	guarantee memory consistency by issuing a cache flush/sync when
+	consistency is needed. If this flag is set V4L2 will attempt to
+	allocate the buffer in non-coherent memory. The flag takes effect
+	only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the
+	queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
+	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
+
+.. raw:: latex
+
+    \normalsize
 
 Timecodes
 =========
diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
index 50ea72043bb0..e59306aba2b0 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
@@ -158,8 +158,9 @@ aborting or finishing any DMA in progress, an implicit
       - This capability is set by the driver to indicate that the queue supports
         cache and memory management hints. However, it's only valid when the
         queue is used for :ref:`memory mapping <mmap>` streaming I/O. See
-        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE <V4L2-BUF-FLAG-NO-CACHE-INVALIDATE>` and
-        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN <V4L2-BUF-FLAG-NO-CACHE-CLEAN>`.
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE <V4L2-BUF-FLAG-NO-CACHE-INVALIDATE>`,
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN <V4L2-BUF-FLAG-NO-CACHE-CLEAN>` and
+        :ref:`V4L2_MEMORY_FLAG_NON_COHERENT <V4L2-MEMORY-FLAG-NON-COHERENT>`.
 
 .. raw:: latex
 
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 9260791b8438..9d11e1d9c934 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -956,6 +956,8 @@ struct v4l2_requestbuffers {
 	__u32			reserved[1];
 };
 
+#define V4L2_MEMORY_FLAG_NON_COHERENT			(1 << 0)
+
 /* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
 #define V4L2_BUF_CAP_SUPPORTS_MMAP			(1 << 0)
 #define V4L2_BUF_CAP_SUPPORTS_USERPTR			(1 << 1)
-- 
2.32.0.432.gabb21c7263-goog


  parent reply	other threads:[~2021-07-27  7:05 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27  7:05 [PATCHv4 0/8] videobuf2: support new noncontiguous DMA API Sergey Senozhatsky
2021-07-27  7:05 ` [PATCHv4 1/8] videobuf2: rework vb2_mem_ops API Sergey Senozhatsky
2021-08-03  8:08   ` Hans Verkuil
2021-08-17 10:41     ` Sergey Senozhatsky
2021-07-27  7:05 ` [PATCHv4 2/8] videobuf2: inverse buffer cache_hints flags Sergey Senozhatsky
2021-07-27  7:05 ` [PATCHv4 3/8] videobuf2: split buffer cache_hints initialisation Sergey Senozhatsky
2021-08-03  8:10   ` Hans Verkuil
2021-08-17 10:41     ` Sergey Senozhatsky
2021-07-27  7:05 ` [PATCHv4 4/8] videobuf2: move cache_hints handling to allocators Sergey Senozhatsky
2021-08-03  8:11   ` Hans Verkuil
2021-08-17 10:42     ` Sergey Senozhatsky
2021-07-27  7:05 ` Sergey Senozhatsky [this message]
2021-08-03  8:12   ` [PATCHv4 5/8] videobuf2: add V4L2_MEMORY_FLAG_NON_COHERENT flag Hans Verkuil
2021-08-17 10:42     ` Sergey Senozhatsky
2021-07-27  7:05 ` [PATCHv4 6/8] videobuf2: add queue memory coherency parameter Sergey Senozhatsky
2021-08-03  8:29   ` Hans Verkuil
2021-08-17 10:43     ` Sergey Senozhatsky
2021-07-27  7:05 ` [PATCHv4 7/8] videobuf2: handle V4L2_MEMORY_FLAG_NON_COHERENT flag Sergey Senozhatsky
2021-08-03  8:31   ` Hans Verkuil
2021-08-17 10:43     ` Sergey Senozhatsky
2021-07-27  7:05 ` [PATCHv4 8/8] videobuf2: handle non-contiguous DMA allocations Sergey Senozhatsky
2021-08-03  8:33   ` Hans Verkuil
2021-08-03  8:39     ` Hans Verkuil
2021-08-23 10:28       ` Sergey Senozhatsky
2021-08-23 10:27     ` Sergey Senozhatsky
2021-08-03 10:15   ` Hans Verkuil
2021-08-17 11:56     ` Sergey Senozhatsky
2021-08-18  9:20       ` Tomasz Figa
2021-08-23 10:29     ` Sergey Senozhatsky

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