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[60.250.196.139]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-20c8bad33b5sm14865485ad.37.2024.10.10.17.31.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Oct 2024 17:31:45 -0700 (PDT) Message-ID: <037102f1-3e8d-4b76-a9d2-a23fde7a502a@gmail.com> Date: Fri, 11 Oct 2024 08:31:41 +0800 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 2/2] mtd: rawnand: nuvoton: add new driver for the Nuvoton MA35 SoC To: Miquel Raynal Cc: richard@nod.at, vigneshr@ti.com, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, nikita.shubin@maquefel.me, arnd@arndb.de, vkoul@kernel.org, esben@geanix.com, linux-arm-kernel@lists.infradead.org, linux-mtd@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240927020749.46791-1-hpchen0nvt@gmail.com> <20240927020749.46791-3-hpchen0nvt@gmail.com> <20241001215755.5c2f8465@xps-13> <8d5e7755-17fd-4860-bcb0-8c1de04bf0c5@gmail.com> <20241008105230.7fd25438@xps-13> <02098767-19ce-407e-88be-24c6259c4053@gmail.com> <20241009100450.362e3556@xps-13> Content-Language: en-US From: Hui-Ping Chen In-Reply-To: <20241009100450.362e3556@xps-13> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Dear Miquel, Thank you for your reply. On 2024/10/9 下午 04:04, Miquel Raynal wrote: > Hi Hui-Ping, > >>>>>> + return 0; >>>>>> + } >>>>>> + >>>>>> + ma35_nand_dmac_init(nand); >>>>>> + >>>>>> + writel(mtd->oobsize, nand->regs + MA35_NFI_REG_NANDRACTL); >>>>>> + >>>>>> + /* setup and start DMA using dma_addr */ >>>>>> + dma_addr = dma_map_single(nand->dev, (void *)addr, len, DMA_FROM_DEVICE); >>>>>> + ret = dma_mapping_error(nand->dev, dma_addr); >>>>>> + if (ret) { >>>>>> + dev_err(nand->dev, "dma mapping error\n"); >>>>>> + return -EINVAL; >>>>>> + } >>>>>> + >>>>>> + writel((unsigned long)dma_addr, nand->regs + MA35_NFI_REG_DMASA); >>>>> Please enforce a dma mask of 32 (even though it might be the fault). >>>> I will change it to dma_addr & 0xffffffff. >>> That's not what I mean, I believe you should use the dma API to ask for >>> a mapping within the accessible 32-bit address range. The >>> dma_mapping_error() check should return an error if that's not the >>> case. Then you can safely write the value. >> Here is my misunderstanding: just fill in the dma_addr directly, >> >> no type conversion is needed. I have already tested it. > FYI, it only works because the default DMA mask for your device is gonna > be 32 bits. If the reality (what your peripheral DMA can do) was > different than this, you would have to set a different mask explicitly > to make sure the dma-mapping step would not provide buffers which are > out of reach. Sure, I will keep that in mind. However, due to the memory architecture of the MA35, which is designed for a maximum of 4GB, there won’t be any situation exceeding 32 bits. Thank you. > Thanks, > Miquèl Best regards, Hui-Ping Chen