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Thu, 12 Dec 2019 13:40:50 +0800 (CST) From: Chen-Yu Tsai To: Russell King Subject: [PATCH v2] ARM: dma-api: fix max_pfn off-by-one error in __dma_supported() Date: Thu, 12 Dec 2019 13:40:47 +0800 Message-Id: <20191212054047.26202-1-wens@kernel.org> X-Mailer: git-send-email 2.24.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191211_214053_712037_2ED75684 X-CRM114-Status: GOOD ( 17.49 ) X-Spam-Score: -5.2 (-----) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-5.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: stable@vger.kernel.org, Chen-Yu Tsai , Christoph Hellwig , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Chen-Yu Tsai max_pfn, as set in arch/arm/mm/init.c: static void __init find_limits(unsigned long *min, unsigned long *max_low, unsigned long *max_high) { *max_low = PFN_DOWN(memblock_get_current_limit()); *min = PFN_UP(memblock_start_of_DRAM()); *max_high = PFN_DOWN(memblock_end_of_DRAM()); } with memblock_end_of_DRAM() pointing to the next byte after DRAM. As such, max_pfn points to the PFN after the end of DRAM. Thus when using max_pfn to check DMA masks, we should subtract one when checking DMA ranges against it. Commit 8bf1268f48ad ("ARM: dma-api: fix off-by-one error in __dma_supported()") fixed the same issue, but missed this spot. This issue was found while working on the sun4i-csi v4l2 driver on the Allwinner R40 SoC. On Allwinner SoCs, DRAM is offset at 0x40000000, and we are starting to use of_dma_configure() with the "dma-ranges" property in the device tree to have the DMA API handle the offset. In this particular instance, dma-ranges was set to the same range as the actual available (2 GiB) DRAM. The following error appeared when the driver attempted to allocate a buffer: sun4i-csi 1c09000.csi: Coherent DMA mask 0x7fffffff (pfn 0x40000-0xc0000) covers a smaller range of system memory than the DMA zone pfn 0x0-0xc0001 sun4i-csi 1c09000.csi: dma_alloc_coherent of size 307200 failed Fixing the off-by-one error makes things work. Fixes: 11a5aa32562e ("ARM: dma-mapping: check DMA mask against available memory") Fixes: 9f28cde0bc64 ("ARM: another fix for the DMA mapping checks") Fixes: ab746573c405 ("ARM: dma-mapping: allow larger DMA mask than supported") Cc: Signed-off-by: Chen-Yu Tsai --- Changes since v1: - correct max_pfn offset in the correct place. --- arch/arm/mm/dma-mapping.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index e822af0d9219..9414d72f664b 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -221,7 +221,7 @@ EXPORT_SYMBOL(arm_coherent_dma_ops); static int __dma_supported(struct device *dev, u64 mask, bool warn) { - unsigned long max_dma_pfn = min(max_pfn, arm_dma_pfn_limit); + unsigned long max_dma_pfn = min(max_pfn - 1, arm_dma_pfn_limit); /* * Translate the device's DMA mask to a PFN limit. This