linux-kernel - [PATCH 4.19 019/113] gpu: host1x: Increase maximum DMA segment size

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Message-Id: <20190729190700.432802400@linuxfoundation.org>
Date:   Mon, 29 Jul 2019 21:21:46 +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, Thierry Reding <treding@...dia.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 019/113] gpu: host1x: Increase maximum DMA segment size

[ Upstream commit 1e390478cfb527e34c9ab89ba57212cb05c33c51 ]

Recent versions of the DMA API debug code have started to warn about
violations of the maximum DMA segment size. This is because the segment
size defaults to 64 KiB, which can easily be exceeded in large buffer
allocations such as used in DRM/KMS for framebuffers.

Technically the Tegra SMMU and ARM SMMU don't have a maximum segment
size (they map individual pages irrespective of whether they are
contiguous or not), so the choice of 4 MiB is a bit arbitrary here. The
maximum segment size is a 32-bit unsigned integer, though, so we can't
set it to the correct maximum size, which would be the size of the
aperture.

Signed-off-by: Thierry Reding <treding@...dia.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/host1x/bus.c | 3 +++
 include/linux/host1x.h   | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/drivers/gpu/host1x/bus.c b/drivers/gpu/host1x/bus.c
index 815bdb42e3f0..0121fe7a4548 100644
--- a/drivers/gpu/host1x/bus.c
+++ b/drivers/gpu/host1x/bus.c
@@ -423,6 +423,9 @@ static int host1x_device_add(struct host1x *host1x,
 
 	of_dma_configure(&device->dev, host1x->dev->of_node, true);
 
+	device->dev.dma_parms = &device->dma_parms;
+	dma_set_max_seg_size(&device->dev, SZ_4M);
+
 	err = host1x_device_parse_dt(device, driver);
 	if (err < 0) {
 		kfree(device);
diff --git a/include/linux/host1x.h b/include/linux/host1x.h
index 89110d896d72..aef6e2f73802 100644
--- a/include/linux/host1x.h
+++ b/include/linux/host1x.h
@@ -310,6 +310,8 @@ struct host1x_device {
 	struct list_head clients;
 
 	bool registered;
+
+	struct device_dma_parameters dma_parms;
 };
 
 static inline struct host1x_device *to_host1x_device(struct device *dev)
-- 
2.20.1