linux-kernel - [PATCH] media: videobuf2-dma-sg: limit the sg segment size

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Message-Id: <20230828075420.2009568-1-anle.pan@nxp.com>
Date:   Mon, 28 Aug 2023 07:54:20 +0000
From:   Anle Pan <anle.pan@....com>
To:     tfiga@...omium.org, m.szyprowski@...sung.com, mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        anle.pan@....com, hui.fang@....com
Subject: [PATCH] media: videobuf2-dma-sg: limit the sg segment size

When allocating from pages, the size of the sg segment is unlimited and
the default is UINT_MAX. This will cause the DMA stream mapping failed
later with a "swiotlb buffer full" error. The default maximum mapping
size is 128 slots x 2K = 256K, determined by "IO_TLB_SEGSIZE".
To fix the issue, limit the sg segment size according to
"dma_max_mapping_size" to match the mapping limit.

Signed-off-by: Anle Pan <anle.pan@....com>
---
 drivers/media/common/videobuf2/videobuf2-dma-sg.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
index fa69158a65b1..b608a7c5f240 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
@@ -105,6 +105,7 @@ static void *vb2_dma_sg_alloc(struct vb2_buffer *vb, struct device *dev,
 	struct sg_table *sgt;
 	int ret;
 	int num_pages;
+	size_t max_segment = 0;
 
 	if (WARN_ON(!dev) || WARN_ON(!size))
 		return ERR_PTR(-EINVAL);
@@ -134,8 +135,12 @@ static void *vb2_dma_sg_alloc(struct vb2_buffer *vb, struct device *dev,
 	if (ret)
 		goto fail_pages_alloc;
 
-	ret = sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
-			buf->num_pages, 0, size, GFP_KERNEL);
+	if (dev)
+		max_segment = dma_max_mapping_size(dev);
+	if (max_segment == 0)
+		max_segment = UINT_MAX;
+	ret = sg_alloc_table_from_pages_segment(buf->dma_sgt, buf->pages,
+		buf->num_pages, 0, size, max_segment, GFP_KERNEL);
 	if (ret)
 		goto fail_table_alloc;
 
-- 
2.25.1