media: platform: fcp: Set appropriate DMA parameters

Enabling CONFIG_DMA_API_DEBUG=y and CONFIG_DMA_API_DEBUG_SG=y will
enable extra validation on DMA operations ensuring that the size
restraints are met.

When using the FCP in conjunction with the VSP1/DU, and display frames,
the size of the DMA operations is larger than the default maximum
segment size reported by the DMA core (64K). With the DMA debug enabled,
this produces a warning such as the following:

"DMA-API: rcar-fcp fea27000.fcp: mapping sg segment longer than device
claims to support [len=3145728] [max=65536]"

We have no specific limitation on the segment size which isn't already
handled by the VSP1/DU which actually handles the DMA allcoations and
buffer management, so define a maximum segment size of up to 4GB (a 32
bit mask).

Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Fixes: 7b49235e83b2 ("[media] v4l: Add Renesas R-Car FCP driver")
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/platform/rcar-fcp.c b/drivers/media/platform/rcar-fcp.c
index 43c78620c9d8a3c04a12468a13124ea780a4b5db..5c6b00737fe75f8e300db165771b727d3a3b2efe 100644 (file)
--- a/drivers/media/platform/rcar-fcp.c
+++ b/drivers/media/platform/rcar-fcp.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/device.h>
+#include <linux/dma-mapping.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
@@ -21,6 +22,7 @@
 struct rcar_fcp_device {
        struct list_head list;
        struct device *dev;
+       struct device_dma_parameters dma_parms;
 };
 
 static LIST_HEAD(fcp_devices);
@@ -136,6 +138,9 @@ static int rcar_fcp_probe(struct platform_device *pdev)
 
        fcp->dev = &pdev->dev;
 
+       fcp->dev->dma_parms = &fcp->dma_parms;
+       dma_set_max_seg_size(fcp->dev, DMA_BIT_MASK(32));
+
        pm_runtime_enable(&pdev->dev);
 
        mutex_lock(&fcp_lock);