@@ -443,6 +443,35 @@ static void vb2_dc_put_userptr(void *buf_priv)
}
/*
+ * To allow mapping scatter-list into signle chunk in DMA address space,
+ * device is required to have DMA max segment size parameter set to value
+ * larger than the buffer size. Otherwise, DMA-mapping subsystem will
+ * split the mapping into max segment size chunks.
+ * This function increases DMA max segment size parameter to let
+ * DMA-mapping to map a buffer as a single chunk in DMA address space.
+ * This code assumes that the DMA-mapping subsystem will merge all
+ * scatter-list segments if this is really possible (for example when
+ * IOMMU is available and enabled).
+ * Ideally, this parameter should be set by generic bus code, but it is
+ * left with the default 64KiB value due to some historical limitations
+ * in other subsystems (like limited USB host drivers) and there is no
+ * good place to set it to the proper value. It is done here to avoid
+ * fixing all vb2-dc client drivers.
+ */
+static int vb2_dc_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;
+}
+
+/*
* For some kind of reserved memory there might be no struct page available,
* so all that can be done to support such 'pages' is to try to convert
* pfn to dma address or at the last resort just assume that
@@ -499,6 +528,10 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
return ERR_PTR(-EINVAL);
}
+ ret = vb2_dc_set_max_seg_size(dev, PAGE_ALIGN(size + PAGE_SIZE));
+ if (!ret)
+ return ERR_PTR(ret);
+
buf = kzalloc(sizeof *buf, GFP_KERNEL);
if (!buf)
return ERR_PTR(-ENOMEM);
@@ -675,10 +708,15 @@ static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
{
struct vb2_dc_buf *buf;
struct dma_buf_attachment *dba;
+ int ret;
if (dbuf->size < size)
return ERR_PTR(-EFAULT);
+ ret = vb2_dc_set_max_seg_size(dev, PAGE_ALIGN(size));
+ if (!ret)
+ return ERR_PTR(ret);
+
buf = kzalloc(sizeof(*buf), GFP_KERNEL);
if (!buf)
return ERR_PTR(-ENOMEM);
@@ -722,6 +760,7 @@ const struct vb2_mem_ops vb2_dma_contig_memops = {
};
EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
+
MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
MODULE_LICENSE("GPL");
This patch lets vb2-dma-contig memory allocator to configure DMA max segment size properly for the client device. Setting it is needed to let DMA-mapping subsystem to create a single, contiguous mapping in DMA address space. This is essential for all devices, which use dma-contig videobuf2 memory allocator and shared buffers (in USERPTR or DMAbuf modes of operations). Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- 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/ As sugested by Hans, configuring DMA max segment size should be done by videobuf2-dma-contig module instead of requiring all device drivers to do it on their own. Here is some 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 --- drivers/media/v4l2-core/videobuf2-dma-contig.c | 39 ++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) -- 1.9.2 -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html