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Wed, 19 Apr 2023 07:22:51 -0700 (PDT) Received: from localhost ([135.180.227.0]) by smtp.gmail.com with ESMTPSA id d2-20020a63d642000000b005140ce70582sm10431557pgj.44.2023.04.19.07.22.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Apr 2023 07:22:51 -0700 (PDT) Date: Wed, 19 Apr 2023 07:22:51 -0700 (PDT) X-Google-Original-Date: Wed, 19 Apr 2023 07:22:44 PDT (-0700) Subject: Re: [PATCH 09/21] riscv: dma-mapping: skip invalidation before bidirectional DMA In-Reply-To: <20230327121317.4081816-10-arnd@kernel.org> CC: linux-kernel@vger.kernel.org, Arnd Bergmann , vgupta@kernel.org, linux@armlinux.org.uk, neil.armstrong@linaro.org, linus.walleij@linaro.org, Catalin Marinas , Will Deacon , guoren@kernel.org, bcain@quicinc.com, geert@linux-m68k.org, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, shorne@gmail.com, deller@gmx.de, mpe@ellerman.id.au, christophe.leroy@csgroup.eu, Paul Walmsley , dalias@libc.org, glaubitz@physik.fu-berlin.de, davem@davemloft.net, jcmvbkbc@gmail.com, Christoph Hellwig , robin.murphy@arm.com, prabhakar.mahadev-lad.rj@bp.renesas.com, Conor Dooley , linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-oxnas@groups.io, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org From: Palmer Dabbelt To: arnd@kernel.org Message-ID: Mime-Version: 1.0 (MHng) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-openrisc@vger.kernel.org On Mon, 27 Mar 2023 05:13:05 PDT (-0700), arnd@kernel.org wrote: > From: Arnd Bergmann > > For a DMA_BIDIRECTIONAL transfer, the caches have to be cleaned > first to let the device see data written by the CPU, and invalidated > after the transfer to let the CPU see data written by the device. > > riscv also invalidates the caches before the transfer, which does > not appear to serve any purpose. > > Signed-off-by: Arnd Bergmann > --- > arch/riscv/mm/dma-noncoherent.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c > index 640f4c496d26..69c80b2155a1 100644 > --- a/arch/riscv/mm/dma-noncoherent.c > +++ b/arch/riscv/mm/dma-noncoherent.c > @@ -25,7 +25,7 @@ void arch_sync_dma_for_device(phys_addr_t paddr, size_t size, > ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size); > break; > case DMA_BIDIRECTIONAL: > - ALT_CMO_OP(flush, vaddr, size, riscv_cbom_block_size); > + ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size); > break; > default: > break; Acked-by: Palmer Dabbelt