On 04/27/2016 02:23 PM, Marek Szyprowski wrote: > 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. This certainly will need to be carefully documented in videobuf2-dma-contig.h. What happens if it is called when you don't have an iommu? Does something break? Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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