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Tue, 17 Jun 2025 00:54:47 -0700 (PDT) Received: from [10.3.15.29] ([217.19.38.130]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-adec81bb9cesm807842966b.49.2025.06.17.00.54.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Jun 2025 00:54:47 -0700 (PDT) Message-ID: <43a834c8f871f8719368b3f3239f27ee4f6c6286.camel@gmail.com> Subject: [PATCH] ARM/dma-mapping: invalidate caches on arch_dma_prep_coherent From: Christian Meissl To: linux-arm-kernel@lists.infradead.org Cc: Russell King , Christoph Hellwig , Philipp Zabel , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org Date: Tue, 17 Jun 2025 09:54:46 +0200 Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" since switching to dma-direct, memory using DMA_ATTR_NO_KERNEL_MAPPING is no longer allocated using the arch specific handlers and instead will use dma_direct_alloc_no_mapping. While the arm specific allocation handlers implicitly clear the allocated dma buffers and will flush any cach= es dma-direct relies on ARCH_HAS_DMA_PREP_COHERENT to flush the caches. Without this flush video frame corruption can occur in drivers like the coda v4l2 driver which explicitly sets the DMA_ATTR_NO_KERNEL_MAPP= ING flag. Fixes: ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally") Signed-off-by: Christian Meissl --- arch/arm/Kconfig | 1 + arch/arm/mm/dma-mapping.c | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 3072731fe09c..7a3aaf3a490b 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -14,6 +14,7 @@ config ARM select ARCH_HAS_DEBUG_VIRTUAL if MMU select ARCH_HAS_DMA_ALLOC if MMU select ARCH_HAS_DMA_OPS + select ARCH_HAS_DMA_PREP_COHERENT select ARCH_HAS_DMA_WRITE_COMBINE if !ARM_DMA_MEM_BUFFERABLE select ARCH_HAS_ELF_RANDOMIZE select ARCH_HAS_FORTIFY_SOURCE diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 88c2d68a69c9..bde7ae4ba31a 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -1821,3 +1821,11 @@ void arch_dma_free(struct device *dev, size_t size, = void *cpu_addr, { __arm_dma_free(dev, size, cpu_addr, dma_handle, attrs, false); } + +void arch_dma_prep_coherent(struct page *page, size_t size) +{ + void *ptr =3D page_address(page); + + dmac_flush_range(ptr, ptr + size); + outer_flush_range(__pa(ptr), __pa(ptr) + size); +} --=20 2.49.0