Re: [PATCHv4 01/11] videobuf2: add cache management members

From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Hans Verkuil <hans.verkuil@cisco.com>,
	Tomasz Figa <tfiga@chromium.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Sakari Ailus <sakari.ailus@iki.fi>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Pawel Osciak <posciak@chromium.org>,
	linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCHv4 01/11] videobuf2: add cache management members
Date: Mon, 9 Mar 2020 12:27:07 +0900	[thread overview]
Message-ID: <20200309032707.GA9460@google.com> (raw)
In-Reply-To: <a4d85ac3-0eea-bc19-cd44-0c8f5b71f6bc@xs4all.nl>

On (20/03/07 12:47), Hans Verkuil wrote:
> 
> Create those tests in v4l2-compliance: that's where they belong.
>
> You need these tests:
> 
> For non-MMAP modes:
> 
> 1) test that V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS is never set.
> 
> If V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS is not set, then:
> 
> 1) attempting to use V4L2_FLAG_MEMORY_NON_CONSISTENT will clear the flag
>    upon return (test with both reqbufs and create_bufs).
> 2) attempting to use V4L2_BUF_FLAG_NO_CACHE_INVALIDATE or V4L2_BUF_FLAG_NO_CACHE_CLEAN
>    will clear those flags upon return (do we actually do that in the patch series?).

NO_CACHE_INVALIDATE/NO_CACHE_CLEAN are cleared in vb2_fill_vb2_v4l2_buffer()
[as was suggested], then the struct is copied back to user. But I think it
would be better to clear those flags when we clear
V4L2_FLAG_MEMORY_NON_CONSISTENT. We have 4 places which do something
like
	"if !vb2_queue_allows_cache_hints(q) then clear flags bit".

Besides, vb2_fill_vb2_v4l2_buffer() is called only for !prepared
buffers, so the flags won't be cleared if the buffer is already
prepared.

Another thing is that, it seems, I need to patch compat32 code. It
copies to user structs member by member so I need to add ->flags.

> If V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS is set, then:
> 
> 1) set V4L2_FLAG_MEMORY_NON_CONSISTENT in reqbufs, but clear in create_bufs:
>    this should fail.
> 2) clear V4L2_FLAG_MEMORY_NON_CONSISTENT in reqbufs, but set in create_bufs:
>    this should fail.
> 3) set V4L2_FLAG_MEMORY_NON_CONSISTENT in both reqbufs and create_bufs: this should
>    work.
> 4) clear V4L2_FLAG_MEMORY_NON_CONSISTENT in both reqbufs and create_bufs: this should
>    work.
> 5) you can use V4L2_BUF_FLAG_NO_CACHE_INVALIDATE or V4L2_BUF_FLAG_NO_CACHE_CLEAN
>    without these flags being cleared in v4l2_buffer.
> 
> All these tests can be done in testReqBufs().

I'm looking into it. Will it work if I patch the vivid test driver to
enable/disable ->allow_cache_hints bit per-node and include the patch
into the series. So then v4l2 tests can create some nodes with
->allow_cache_hints.  Something like this:

---
 drivers/media/platform/vivid/vivid-core.c     | 6 +++++-
 drivers/media/platform/vivid/vivid-core.h     | 1 +
 drivers/media/platform/vivid/vivid-meta-cap.c | 3 +++
 drivers/media/platform/vivid/vivid-meta-out.c | 3 +++
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/vivid/vivid-core.c b/drivers/media/platform/vivid/vivid-core.c
index c62c068b6b60..9acbb59d240c 100644
--- a/drivers/media/platform/vivid/vivid-core.c
+++ b/drivers/media/platform/vivid/vivid-core.c
@@ -129,7 +129,8 @@ MODULE_PARM_DESC(node_types, " node types, default is 0xe1d3d. Bitmask with the
 			     "\t\t    bit 16: Framebuffer for testing overlays\n"
 			     "\t\t    bit 17: Metadata Capture node\n"
 			     "\t\t    bit 18: Metadata Output node\n"
-			     "\t\t    bit 19: Touch Capture node\n");
+			     "\t\t    bit 19: Touch Capture node\n"
+			     "\t\t    bit 20: Node supports cache-hints\n");
 
 /* Default: 4 inputs */
 static unsigned num_inputs[VIVID_MAX_DEVS] = { [0 ... (VIVID_MAX_DEVS - 1)] = 4 };
@@ -977,6 +978,9 @@ static int vivid_create_instance(struct platform_device *pdev, int inst)
 		return -EINVAL;
 	}
 
+	/* do we enable user-space cache management hints */
+	dev->allow_cache_hints = node_type & 0x100000;
+
 	/* do we create a radio receiver device? */
 	dev->has_radio_rx = node_type & 0x0010;
 
diff --git a/drivers/media/platform/vivid/vivid-core.h b/drivers/media/platform/vivid/vivid-core.h
index 99e69b8f770f..2d311fc33619 100644
--- a/drivers/media/platform/vivid/vivid-core.h
+++ b/drivers/media/platform/vivid/vivid-core.h
@@ -206,6 +206,7 @@ struct vivid_dev {
 	bool				has_meta_out;
 	bool				has_tv_tuner;
 	bool				has_touch_cap;
+	bool				allow_cache_hints;
 
 	bool				can_loop_video;
 
diff --git a/drivers/media/platform/vivid/vivid-meta-cap.c b/drivers/media/platform/vivid/vivid-meta-cap.c
index 780f96860a6d..6c28034d3d58 100644
--- a/drivers/media/platform/vivid/vivid-meta-cap.c
+++ b/drivers/media/platform/vivid/vivid-meta-cap.c
@@ -33,6 +33,9 @@ static int meta_cap_queue_setup(struct vb2_queue *vq, unsigned int *nbuffers,
 	if (vq->num_buffers + *nbuffers < 2)
 		*nbuffers = 2 - vq->num_buffers;
 
+	if (dev->allow_cache_hints)
+		vq->allow_cache_hints = true;
+
 	*nplanes = 1;
 	return 0;
 }
diff --git a/drivers/media/platform/vivid/vivid-meta-out.c b/drivers/media/platform/vivid/vivid-meta-out.c
index ff8a039aba72..d7b808aa5f6d 100644
--- a/drivers/media/platform/vivid/vivid-meta-out.c
+++ b/drivers/media/platform/vivid/vivid-meta-out.c
@@ -33,6 +33,9 @@ static int meta_out_queue_setup(struct vb2_queue *vq, unsigned int *nbuffers,
 	if (vq->num_buffers + *nbuffers < 2)
 		*nbuffers = 2 - vq->num_buffers;
 
+	if (dev->allow_cache_hints)
+		vq->allow_cache_hints = true;
+
 	*nplanes = 1;
 	return 0;
 }
-- 
2.25.1

