[PATCH v5 0/2] vb2-dma-contig: configure DMA max segment size properly

[PATCH v5 0/2] vb2-dma-contig: configure DMA max segment size properly

[Marek Szyprowski]

Hello,

This patch is a follow-up of my previous attempts to let Exynos
multimedia devices to work properly with shared buffers when IOMMU is
enabled:
1. https://www.mail-archive.com/linux-media@vger.kernel.org/msg96946.html
2. http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/97316
3. https://patchwork.linuxtv.org/patch/30870/
4. http://www.spinics.net/lists/linux-media/msg100353.html

After another discussion (4th link above) I agree with Mauro that
changing dma_parms should be done from device drivers not the
videobuf2-dc module. Now drivers releases dma_parms structure (allocated
by vb2_dc_set_max_seg_size()), which in theory might be allocated by
other function than vb2_dc_set_max_seg_size(). This is however not a big
issue, because no such case exist in mainline kernel (there is no
generic bus code for platform devices, which allocates dma_parms
structure).

Here is some more backgroud why this is done in videobuf2-dc not in the
respective generic bus code:
http://lists.infradead.org/pipermail/linux-arm-kernel/2014-November/305913.html

Best regards,
Marek Szyprowski

changelog:
v5:
- got back to the v1-style version on Mauro request
- added function to clear dma_parms and release allocated structure

v4: http://www.spinics.net/lists/linux-media/msg100182.html
- rebased onto media master tree
- call vb2_dc_set_max_seg_size after allocating vb2 buf object

v3: http://www.spinics.net/lists/linux-media/msg100125.html
- added FIXME note about possible memory leak

v2: http://www.spinics.net/lists/linux-media/msg100011.html
- fixes typos and other language issues in the comments

v1: http://article.gmane.org/gmane.linux.kernel.samsung-soc/53690

Marek Szyprowski (2):
  media: vb2-dma-contig: add helper for setting dma max seg size
  media: set proper max seg size for devices on Exynos SoCs

 drivers/media/platform/exynos-gsc/gsc-core.c   |  2 +
 drivers/media/platform/exynos4-is/fimc-core.c  |  2 +
 drivers/media/platform/exynos4-is/fimc-is.c    |  2 +
 drivers/media/platform/exynos4-is/fimc-lite.c  |  2 +
 drivers/media/platform/s5p-g2d/g2d.c           |  2 +
 drivers/media/platform/s5p-jpeg/jpeg-core.c    |  2 +
 drivers/media/platform/s5p-mfc/s5p_mfc.c       |  4 ++
 drivers/media/platform/s5p-tv/mixer_video.c    |  2 +
 drivers/media/v4l2-core/videobuf2-dma-contig.c | 53 ++++++++++++++++++++++++++
 include/media/videobuf2-dma-contig.h           |  2 +
 10 files changed, 73 insertions(+)

-- 
1.9.2

[PATCH v5 1/2] media: vb2-dma-contig: add helper for setting dma max seg size

[Marek Szyprowski]

Add a helper function for device drivers to set DMA's max_seg_size.
Setting it to largest possible value lets DMA-mapping API always create
contiguous mappings in DMA address space. This is essential for all
devices, which use dma-contig videobuf2 memory allocator and shared
buffers.

Till now, the only case when vb2-dma-contig really 'worked' was a case
where userspace provided USERPTR buffer, which was in fact mmaped
contiguous buffer from the other v4l2/drm device. Also DMABUF made of
contiguous buffer worked only when its exporter did not split it into
several chunks in the scatter-list. Any other buffer failed, regardless
of the arch/platform used and the presence of the IOMMU of the device bus.

This patch provides interface to fix this issue.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c | 53 ++++++++++++++++++++++++++
 include/media/videobuf2-dma-contig.h           |  2 +
 2 files changed, 55 insertions(+)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 5361197..e3e47ac 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -753,6 +753,59 @@ void vb2_dma_contig_cleanup_ctx(void *alloc_ctx)
 }
 EXPORT_SYMBOL_GPL(vb2_dma_contig_cleanup_ctx);
 
+/**
+ * vb2_dma_contig_set_max_seg_size() - configure DMA max segment size
+ * @dev:	device for configuring DMA parameters
+ * @size:	size of DMA max segment size to set
+ *
+ * To allow mapping the scatter-list into a single chunk in the DMA
+ * address space, the device is required to have the DMA max segment
+ * size parameter set to a value larger than the buffer size. Otherwise,
+ * the DMA-mapping subsystem will split the mapping into max segment
+ * size chunks. This function sets the DMA max segment size
+ * parameter to let DMA-mapping map a buffer as a single chunk in DMA
+ * address space.
+ * This code assumes that the DMA-mapping subsystem will merge all
+ * scatterlist segments if this is really possible (for example when
+ * an IOMMU is available and enabled).
+ * Ideally, this parameter should be set by the generic bus code, but it
+ * is left with the default 64KiB value due to historical litmiations in
+ * other subsystems (like limited USB host drivers) and there no good
+ * place to set it to the proper value.
+ * This function should be called from the drivers, which are known to
+ * operate on platforms with IOMMU and provide access to shared buffers
+ * (either USERPTR or DMABUF). This should be done before initializing
+ * videobuf2 queue.
+ */
+int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
+{
+	if (!dev->dma_parms) {
+		dev->dma_parms = kzalloc(sizeof(dev->dma_parms), GFP_KERNEL);
+		if (!dev->dma_parms)
+			return -ENOMEM;
+	}
+	if (dma_get_max_seg_size(dev) < size)
+		return dma_set_max_seg_size(dev, size);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
+
+/*
+ * vb2_dma_contig_clear_max_seg_size() - release resources for DMA parameters
+ * @dev:	device for configuring DMA parameters
+ *
+ * This function releases resources allocated to configure DMA parameters
+ * (see vb2_dma_contig_set_max_seg_size() function). It should be called from
+ * device drivers on driver remove.
+ */
+void vb2_dma_contig_clear_max_seg_size(struct device *dev)
+{
+	kfree(dev->dma_parms);
+	dev->dma_parms = NULL;
+}
+EXPORT_SYMBOL_GPL(vb2_dma_contig_clear_max_seg_size);
+
 MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
 MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
 MODULE_LICENSE("GPL");
diff --git a/include/media/videobuf2-dma-contig.h b/include/media/videobuf2-dma-contig.h
index 2087c9a..f7dc840 100644
--- a/include/media/videobuf2-dma-contig.h
+++ b/include/media/videobuf2-dma-contig.h
@@ -35,6 +35,8 @@ static inline void *vb2_dma_contig_init_ctx(struct device *dev)
 }
 
 void vb2_dma_contig_cleanup_ctx(void *alloc_ctx);
+int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size);
+void vb2_dma_contig_clear_max_seg_size(struct device *dev);
 
 extern const struct vb2_mem_ops vb2_dma_contig_memops;
 
-- 
1.9.2

[PATCH v5 2/2] media: set proper max seg size for devices on Exynos SoCs

[Marek Szyprowski]

All multimedia devices found on Exynos SoCs support only contiguous
buffers, so set DMA max segment size to DMA_BIT_MASK(32) to let memory
allocator to correctly create contiguous memory mappings.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/media/platform/exynos-gsc/gsc-core.c  | 2 ++
 drivers/media/platform/exynos4-is/fimc-core.c | 2 ++
 drivers/media/platform/exynos4-is/fimc-is.c   | 2 ++
 drivers/media/platform/exynos4-is/fimc-lite.c | 2 ++
 drivers/media/platform/s5p-g2d/g2d.c          | 2 ++
 drivers/media/platform/s5p-jpeg/jpeg-core.c   | 2 ++
 drivers/media/platform/s5p-mfc/s5p_mfc.c      | 4 ++++
 drivers/media/platform/s5p-tv/mixer_video.c   | 2 ++
 8 files changed, 18 insertions(+)

diff --git a/drivers/media/platform/exynos-gsc/gsc-core.c b/drivers/media/platform/exynos-gsc/gsc-core.c
index c049736..c9d2009 100644
--- a/drivers/media/platform/exynos-gsc/gsc-core.c
+++ b/drivers/media/platform/exynos-gsc/gsc-core.c
@@ -1124,6 +1124,7 @@ static int gsc_probe(struct platform_device *pdev)
 		goto err_m2m;
 
 	/* Initialize continious memory allocator */
+	vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32));
 	gsc->alloc_ctx = vb2_dma_contig_init_ctx(dev);
 	if (IS_ERR(gsc->alloc_ctx)) {
 		ret = PTR_ERR(gsc->alloc_ctx);
@@ -1153,6 +1154,7 @@ static int gsc_remove(struct platform_device *pdev)
 	v4l2_device_unregister(&gsc->v4l2_dev);
 
 	vb2_dma_contig_cleanup_ctx(gsc->alloc_ctx);
+	vb2_dma_contig_clear_max_seg_size(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 	gsc_clk_put(gsc);
 
diff --git a/drivers/media/platform/exynos4-is/fimc-core.c b/drivers/media/platform/exynos4-is/fimc-core.c
index b1c1cea..368f44f 100644
--- a/drivers/media/platform/exynos4-is/fimc-core.c
+++ b/drivers/media/platform/exynos4-is/fimc-core.c
@@ -1019,6 +1019,7 @@ static int fimc_probe(struct platform_device *pdev)
 	}
 
 	/* Initialize contiguous memory allocator */
+	vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32));
 	fimc->alloc_ctx = vb2_dma_contig_init_ctx(dev);
 	if (IS_ERR(fimc->alloc_ctx)) {
 		ret = PTR_ERR(fimc->alloc_ctx);
@@ -1124,6 +1125,7 @@ static int fimc_remove(struct platform_device *pdev)
 
 	fimc_unregister_capture_subdev(fimc);
 	vb2_dma_contig_cleanup_ctx(fimc->alloc_ctx);
+	vb2_dma_contig_clear_max_seg_size(&pdev->dev);
 
 	clk_disable(fimc->clock[CLK_BUS]);
 	fimc_clk_put(fimc);
diff --git a/drivers/media/platform/exynos4-is/fimc-is.c b/drivers/media/platform/exynos4-is/fimc-is.c
index 979c388..bd98b56 100644
--- a/drivers/media/platform/exynos4-is/fimc-is.c
+++ b/drivers/media/platform/exynos4-is/fimc-is.c
@@ -847,6 +847,7 @@ static int fimc_is_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto err_pm;
 
+	vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32));
 	is->alloc_ctx = vb2_dma_contig_init_ctx(dev);
 	if (IS_ERR(is->alloc_ctx)) {
 		ret = PTR_ERR(is->alloc_ctx);
@@ -940,6 +941,7 @@ static int fimc_is_remove(struct platform_device *pdev)
 	free_irq(is->irq, is);
 	fimc_is_unregister_subdevs(is);
 	vb2_dma_contig_cleanup_ctx(is->alloc_ctx);
+	vb2_dma_contig_clear_max_seg_size(dev);
 	fimc_is_put_clocks(is);
 	fimc_is_debugfs_remove(is);
 	release_firmware(is->fw.f_w);
diff --git a/drivers/media/platform/exynos4-is/fimc-lite.c b/drivers/media/platform/exynos4-is/fimc-lite.c
index dc1b929..27cb620 100644
--- a/drivers/media/platform/exynos4-is/fimc-lite.c
+++ b/drivers/media/platform/exynos4-is/fimc-lite.c
@@ -1551,6 +1551,7 @@ static int fimc_lite_probe(struct platform_device *pdev)
 			goto err_sd;
 	}
 
+	vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32));
 	fimc->alloc_ctx = vb2_dma_contig_init_ctx(dev);
 	if (IS_ERR(fimc->alloc_ctx)) {
 		ret = PTR_ERR(fimc->alloc_ctx);
@@ -1652,6 +1653,7 @@ static int fimc_lite_remove(struct platform_device *pdev)
 	pm_runtime_set_suspended(dev);
 	fimc_lite_unregister_capture_subdev(fimc);
 	vb2_dma_contig_cleanup_ctx(fimc->alloc_ctx);
+	vb2_dma_contig_clear_max_seg_size(dev);
 	fimc_lite_clk_put(fimc);
 
 	dev_info(dev, "Driver unloaded\n");
diff --git a/drivers/media/platform/s5p-g2d/g2d.c b/drivers/media/platform/s5p-g2d/g2d.c
index 612d1ea..d3e3469 100644
--- a/drivers/media/platform/s5p-g2d/g2d.c
+++ b/drivers/media/platform/s5p-g2d/g2d.c
@@ -681,6 +681,7 @@ static int g2d_probe(struct platform_device *pdev)
 		goto put_clk_gate;
 	}
 
+	vb2_dma_contig_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32));
 	dev->alloc_ctx = vb2_dma_contig_init_ctx(&pdev->dev);
 	if (IS_ERR(dev->alloc_ctx)) {
 		ret = PTR_ERR(dev->alloc_ctx);
@@ -757,6 +758,7 @@ static int g2d_remove(struct platform_device *pdev)
 	video_unregister_device(dev->vfd);
 	v4l2_device_unregister(&dev->v4l2_dev);
 	vb2_dma_contig_cleanup_ctx(dev->alloc_ctx);
+	vb2_dma_contig_clear_max_seg_size(&pdev->dev);
 	clk_unprepare(dev->gate);
 	clk_put(dev->gate);
 	clk_unprepare(dev->clk);
diff --git a/drivers/media/platform/s5p-jpeg/jpeg-core.c b/drivers/media/platform/s5p-jpeg/jpeg-core.c
index caa19b4..17bc94092 100644
--- a/drivers/media/platform/s5p-jpeg/jpeg-core.c
+++ b/drivers/media/platform/s5p-jpeg/jpeg-core.c
@@ -2843,6 +2843,7 @@ static int s5p_jpeg_probe(struct platform_device *pdev)
 		goto device_register_rollback;
 	}
 
+	vb2_dma_contig_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32));
 	jpeg->alloc_ctx = vb2_dma_contig_init_ctx(&pdev->dev);
 	if (IS_ERR(jpeg->alloc_ctx)) {
 		v4l2_err(&jpeg->v4l2_dev, "Failed to init memory allocator\n");
@@ -2942,6 +2943,7 @@ static int s5p_jpeg_remove(struct platform_device *pdev)
 	video_unregister_device(jpeg->vfd_decoder);
 	video_unregister_device(jpeg->vfd_encoder);
 	vb2_dma_contig_cleanup_ctx(jpeg->alloc_ctx);
+	vb2_dma_contig_clear_max_seg_size(&pdev->dev);
 	v4l2_m2m_release(jpeg->m2m_dev);
 	v4l2_device_unregister(&jpeg->v4l2_dev);
 
diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc.c b/drivers/media/platform/s5p-mfc/s5p_mfc.c
index b16466f..274473e 100644
--- a/drivers/media/platform/s5p-mfc/s5p_mfc.c
+++ b/drivers/media/platform/s5p-mfc/s5p_mfc.c
@@ -1164,11 +1164,13 @@ static int s5p_mfc_probe(struct platform_device *pdev)
 		}
 	}
 
+	vb2_dma_contig_set_max_seg_size(dev->mem_dev_l, DMA_BIT_MASK(32));
 	dev->alloc_ctx[0] = vb2_dma_contig_init_ctx(dev->mem_dev_l);
 	if (IS_ERR(dev->alloc_ctx[0])) {
 		ret = PTR_ERR(dev->alloc_ctx[0]);
 		goto err_res;
 	}
+	vb2_dma_contig_set_max_seg_size(dev->mem_dev_r, DMA_BIT_MASK(32));
 	dev->alloc_ctx[1] = vb2_dma_contig_init_ctx(dev->mem_dev_r);
 	if (IS_ERR(dev->alloc_ctx[1])) {
 		ret = PTR_ERR(dev->alloc_ctx[1]);
@@ -1293,6 +1295,8 @@ static int s5p_mfc_remove(struct platform_device *pdev)
 	s5p_mfc_release_firmware(dev);
 	vb2_dma_contig_cleanup_ctx(dev->alloc_ctx[0]);
 	vb2_dma_contig_cleanup_ctx(dev->alloc_ctx[1]);
+	vb2_dma_contig_clear_max_seg_size(dev->mem_dev_l);
+	vb2_dma_contig_clear_max_seg_size(dev->mem_dev_r);
 	if (pdev->dev.of_node) {
 		put_device(dev->mem_dev_l);
 		put_device(dev->mem_dev_r);
diff --git a/drivers/media/platform/s5p-tv/mixer_video.c b/drivers/media/platform/s5p-tv/mixer_video.c
index 7ab5578..123d271 100644
--- a/drivers/media/platform/s5p-tv/mixer_video.c
+++ b/drivers/media/platform/s5p-tv/mixer_video.c
@@ -80,6 +80,7 @@ int mxr_acquire_video(struct mxr_device *mdev,
 		goto fail;
 	}
 
+	vb2_dma_contig_set_max_seg_size(mdev->dev, DMA_BIT_MASK(32));
 	mdev->alloc_ctx = vb2_dma_contig_init_ctx(mdev->dev);
 	if (IS_ERR(mdev->alloc_ctx)) {
 		mxr_err(mdev, "could not acquire vb2 allocator\n");
@@ -152,6 +153,7 @@ void mxr_release_video(struct mxr_device *mdev)
 		kfree(mdev->output[i]);
 
 	vb2_dma_contig_cleanup_ctx(mdev->alloc_ctx);
+	vb2_dma_contig_clear_max_seg_size(mdev->dev);
 	v4l2_device_unregister(&mdev->v4l2_dev);
 }
 
-- 
1.9.2

[PATCH next] [media] vb2: Fix allocation size of dma_parms

[Vincent Stehlé]

When allocating memory to hold the device dma parameters in
vb2_dma_contig_set_max_seg_size(), the requested size is by mistake only
the size of a pointer. Request the correct size instead.

Fixes: 3f0339691896 ("media: vb2-dma-contig: add helper for setting dma max seg size")
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
---


Hi,

I saw that in linux next-20160718.

Best regards,

Vincent.


 drivers/media/v4l2-core/videobuf2-dma-contig.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index b09b2c9..59fa204 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -743,7 +743,7 @@ EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
 int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
 {
 	if (!dev->dma_parms) {
-		dev->dma_parms = kzalloc(sizeof(dev->dma_parms), GFP_KERNEL);
+		dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
 		if (!dev->dma_parms)
 			return -ENOMEM;
 	}
-- 
2.8.1

Re: [PATCH next] [media] vb2: Fix allocation size of dma_parms

[Marek Szyprowski]

Hi


On 2016-07-18 19:54, Vincent Stehlé wrote:
> When allocating memory to hold the device dma parameters in
> vb2_dma_contig_set_max_seg_size(), the requested size is by mistake only
> the size of a pointer. Request the correct size instead.
>
> Fixes: 3f0339691896 ("media: vb2-dma-contig: add helper for setting dma max seg size")
> Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>

I'm really sorry for such silly mistake. Thanks for spotting this issue.

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
>
>
> Hi,
>
> I saw that in linux next-20160718.
>
> Best regards,
>
> Vincent.
>
>
>   drivers/media/v4l2-core/videobuf2-dma-contig.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> index b09b2c9..59fa204 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> @@ -743,7 +743,7 @@ EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
>   int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
>   {
>   	if (!dev->dma_parms) {
> -		dev->dma_parms = kzalloc(sizeof(dev->dma_parms), GFP_KERNEL);
> +		dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
>   		if (!dev->dma_parms)
>   			return -ENOMEM;
>   	}

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland