linux-kernel - [PATCH] [media] videobuf2-dma-contig: Support cacheable MMAP

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Date:   Fri, 14 Oct 2016 15:21:49 +0200
From:   Thierry Escande <thierry.escande@...labora.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pawel Osciak <pawel@...iak.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>
Subject: [PATCH] [media] videobuf2-dma-contig: Support cacheable MMAP

From: Heng-Ruey Hsu <henryhsu@...omium.org>

DMA allocations for MMAP type are uncached by default. But for
some cases, CPU has to access the buffers. ie: memcpy for format
converter. Supporting cacheable MMAP improves huge performance.

Signed-off-by: Heng-Ruey Hsu <henryhsu@...omium.org>
Tested-by: Heng-ruey Hsu <henryhsu@...omium.org>
Reviewed-by: Tomasz Figa <tfiga@...omium.org>
Signed-off-by: Thierry Escande <thierry.escande@...labora.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index fb6a177..c953c24 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -42,6 +42,12 @@ struct vb2_dc_buf {
 };
 
 /*********************************************/
+/*           Forward declarations            */
+/*********************************************/
+
+static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf);
+
+/*********************************************/
 /*        scatterlist table functions        */
 /*********************************************/
 
@@ -129,6 +135,10 @@ static void vb2_dc_put(void *buf_priv)
 		sg_free_table(buf->sgt_base);
 		kfree(buf->sgt_base);
 	}
+	if (buf->dma_sgt) {
+		sg_free_table(buf->dma_sgt);
+		kfree(buf->dma_sgt);
+	}
 	dma_free_attrs(buf->dev, buf->size, buf->cookie, buf->dma_addr,
 		       buf->attrs);
 	put_device(buf->dev);
@@ -170,6 +180,10 @@ static void *vb2_dc_alloc(struct device *dev, unsigned long attrs,
 	buf->handler.put = vb2_dc_put;
 	buf->handler.arg = buf;
 
+	if (!(buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
+	     (buf->attrs & DMA_ATTR_NON_CONSISTENT))
+		buf->dma_sgt = vb2_dc_get_base_sgt(buf);
+
 	atomic_inc(&buf->refcount);
 
 	return buf;
@@ -205,6 +219,11 @@ static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
 
 	vma->vm_ops->open(vma);
 
+	if ((buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
+	    (buf->attrs & DMA_ATTR_NON_CONSISTENT) &&
+	    !buf->dma_sgt)
+		buf->dma_sgt = vb2_dc_get_base_sgt(buf);
+
 	pr_debug("%s: mapped dma addr 0x%08lx at 0x%08lx, size %ld\n",
 		__func__, (unsigned long)buf->dma_addr, vma->vm_start,
 		buf->size);
-- 
2.7.4