linux-kernel - [PATCH 4.9 071/128] media: platform: fcp: Set appropriate DMA parameters

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Date:   Fri, 19 Jun 2020 16:32:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 071/128] media: platform: fcp: Set appropriate DMA parameters

From: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>

[ Upstream commit dd844fb8e50b12e65bbdc5746c9876c6735500df ]

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@...der.be>
Fixes: 7b49235e83b2 ("[media] v4l: Add Renesas R-Car FCP driver")
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/platform/rcar-fcp.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/media/platform/rcar-fcp.c b/drivers/media/platform/rcar-fcp.c
index f3a3f31cdfa9..8e9c3bd36d03 100644
--- a/drivers/media/platform/rcar-fcp.c
+++ b/drivers/media/platform/rcar-fcp.c
@@ -12,6 +12,7 @@
  */
 
 #include <linux/device.h>
+#include <linux/dma-mapping.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -24,6 +25,7 @@
 struct rcar_fcp_device {
 	struct list_head list;
 	struct device *dev;
+	struct device_dma_parameters dma_parms;
 };
 
 static LIST_HEAD(fcp_devices);
@@ -140,6 +142,9 @@ 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);
-- 
2.25.1