linux-kernel - [PATCH 8/8] media: platform: s5p-mfc: use DMA_ATTR_LOW

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Message-Id: <20200925141218.13550-9-m.szyprowski@samsung.com>
Date:   Fri, 25 Sep 2020 16:12:18 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Linux IOMMU <iommu@...ts.linux-foundation.org>,
        linux-media@...r.kernel.org, linux-samsung-soc@...r.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>, Christoph Hellwig <hch@....de>,
        Sylwester Nawrocki <snawrocki@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Tomasz Figa <tfiga@...omium.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 8/8] media: platform: s5p-mfc: use DMA_ATTR_LOW_ADDRESS

S5P-MFC driver relied on the way the ARM DMA-IOMMU glue code worked -
mainly it relied on the fact that the allocator used first-fit algorithm
and the first allocated buffer were at 0x0 DMA/IOVA address. This is not
true for the generic IOMMU-DMA glue code that will be used for ARM
architecture soon, so limit the dma_mask to size of the DMA window the
hardware can use and add the needed DMA attribute to force proper IOVA
allocation of the firmware buffer.

Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
---
 drivers/media/platform/s5p-mfc/s5p_mfc.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc.c b/drivers/media/platform/s5p-mfc/s5p_mfc.c
index eba2b9f040df..171fd9fd22e4 100644
--- a/drivers/media/platform/s5p-mfc/s5p_mfc.c
+++ b/drivers/media/platform/s5p-mfc/s5p_mfc.c
@@ -1199,8 +1199,12 @@ static int s5p_mfc_configure_common_memory(struct s5p_mfc_dev *mfc_dev)
 	if (!mfc_dev->mem_bitmap)
 		return -ENOMEM;
 
-	mfc_dev->mem_virt = dma_alloc_coherent(dev, mem_size,
-					       &mfc_dev->mem_base, GFP_KERNEL);
+	/* MFC v5 can access memory only via the 256M window */
+	if (exynos_is_iommu_available(dev) && !IS_MFCV6_PLUS(mfc_dev))
+		dma_set_mask_and_coherent(dev, SZ_256M - 1);
+
+	mfc_dev->mem_virt = dma_alloc_attrs(dev, mem_size, &mfc_dev->mem_base,
+					    GFP_KERNEL, DMA_ATTR_LOW_ADDRESS);
 	if (!mfc_dev->mem_virt) {
 		kfree(mfc_dev->mem_bitmap);
 		dev_err(dev, "failed to preallocate %ld MiB for the firmware and context buffers\n",
-- 
2.17.1