Hello,
On 2016-04-27 14:10, Hans Verkuil wrote:
On 04/27/2016 02:00 PM, Marek Szyprowski wrote:
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.
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
This patch was posted earlier as a part of
http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/97316
thread, but applying it is really needed to get all Exynos multimedia
drivers working with IOMMU enabled.
Best regards,
Marek Szyprowski
---
drivers/media/v4l2-core/videobuf2-dma-contig.c | 15 +++++++++++++++
include/media/videobuf2-dma-contig.h | 1 +
2 files changed, 16 insertions(+)
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 5361197..f611456 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -753,6 +753,21 @@ void vb2_dma_contig_cleanup_ctx(void *alloc_ctx)
}
EXPORT_SYMBOL_GPL(vb2_dma_contig_cleanup_ctx);
+int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
+{
+ if (!dev->dma_parms) {
+ dev->dma_parms = devm_kzalloc(dev, sizeof(dev->dma_parms),
+ GFP_KERNEL);
The v3 patch from December uses kzalloc here. Is this perhaps on old version?
Right, my fault. I will do another resend (and fix the typo in the
second patch).
+ 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);
Admittedly I haven't looked closely at this, but is this something that you
want for all dma-contig devices? Or to rephrase this question: what type of
devices will need this?
This is needed for all devices using vb2-dc, iommu and user-ptr mode,
however
in the previous discussions (see https://patchwork.linuxtv.org/patch/30870/
) it has been suggested to make it via common helper instead of forcing it
in vb2-dc.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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