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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH 1/3] spi: s3c64xx: support spi polling mode using devicetree Content-Language: en-US To: Mark Brown Cc: Krzysztof Kozlowski , Andi Shyti , Alim Akhtar , Rob Herring , linux-spi@vger.kernel.org, linux-samsung-soc@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Chanho Park From: Jaewon Kim In-Reply-To: Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrLJsWRmVeSWpSXmKPExsWy7bCmhe4pdp0Ug1/PmC0ezNvGZrH4x3Mm i6kPn7BZXN6vbTH/yDlWi72vt7JbbHp8jdXi8q45bBYzzu9jsmj8eJPdonXvEXYHbo/rSz4x e2xa1cnmcefaHjaPzUvqPfq2rGL0+LxJLoAtKtsmIzUxJbVIITUvOT8lMy/dVsk7ON453tTM wFDX0NLCXEkhLzE31VbJxSdA1y0zB+g6JYWyxJxSoFBAYnGxkr6dTVF+aUmqQkZ+cYmtUmpB Sk6BeYFecWJucWleul5eaomVoYGBkSlQYUJ2xqkdexgLergq5j49w9TA+JO9i5GTQ0LAROLH pPusXYxcHEICOxglvu3byAbhfGKUOHv8PhOE841Rouf7XCaYlrtLj7JAJPYySjy+eYsNJCEk 8JpRYtkEWxCbV8BO4t+nrSwgNouAisSsAxeYIOKCEidnPgGLiwpESfTd3sQKYgsLBEmsPHgf zGYWEJe49WQ+WL2IgLLE1e97wZYxC3xkkrg1cxJYgk1AW+L7+sVADRwcnAKOEn1rOCB65SW2 v53DDFIvIbCSQ2LB1MlsEFe7SDw/NpMFwhaWeHV8CzQApCQ+v9sLVZMt0T79DyuEXSFxccNs qLixxKxn7Ywgu5gFNCXW79IHMSWAbjtyiwViLZ9Ex+G/7BBhXomONiGIRjWJ+1PPQQ2RkZh0 ZCU0CD0kjv7cxjSBUXEWUqDMQvL8LCTPzELYu4CRZRWjWGpBcW56arFRgQk8rpPzczcxgtOt lscOxtlvP+gdYmTiYDzEKMHBrCTCq9qllSLEm5JYWZValB9fVJqTWnyI0RQYNROZpUST84EJ P68k3tDE0sDEzMzQ3MjUwFxJnPdjh3KKkEB6YklqdmpqQWoRTB8TB6dUA9OUSb9crI4IbV+8 T9lg9lkVU6M9W70nt2d7b2ubJ/Dm6vyE6XWn/jFkzFNel2h0QqZsTsYBaanr6seKzdZYZP04 /XveQpH7LtfO52R8Tp/TVj9dNSe3+E3728/LlDOfX4yMyjs753xdURrTdKGo24ZPfLfM9jjy eunCdbdL3jFdnLRiXl1ep8Hm5bX5RvL/HU2mTdO9xpzZox/du3vyPPZlvtxr+eYt2pNSoilb e+/i5QR36+lfur/J2J74qbJ+6STfLe17+eoyZirPS98bID/95dmNqklC/5j2f09/qu66mv+G TA1nS8o92f0nji2Sf/66QyyC9c3xg7PNSyfo9G4IY23Zq/mnrDX4kZ0cU1WiEktxRqKhFnNR cSIAkSYmwkAEAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFupjkeLIzCtJLcpLzFFi42LZdlhJTvcku06KQcNeJYsH87axWSz+8ZzJ YurDJ2wWl/drW8w/co7VYu/rrewWmx5fY7W4vGsOm8WM8/uYLBo/3mS3aN17hN2B2+P6kk/M HptWdbJ53Lm2h81j85J6j74tqxg9Pm+SC2CL4rJJSc3JLEst0rdL4Mo4tWMPY0EPV8Xcp2eY Ghh/sncxcnJICJhI3F16lKWLkYtDSGA3o8Tkl6vYIBIyEsuf9UHZwhL3W46wQhS9ZJQ4eWY1 I0iCV8BO4t+nrSwgNouAisSsAxeYIOKCEidnPgGLiwpESXw+0AK2TVggSGLlwfusIDazgLjE rSfzwepFBJQlrn7fywIR/8gkMWmCOMSyf4wS05YsAytiE9CW+L5+MVAzBwengKNE3xoOiHoz ia6tXYwQtrzE9rdzmCcwCs1CcsYsJOtmIWmZhaRlASPLKkbJ1ILi3PTcYsMCw7zUcr3ixNzi 0rx0veT83E2M4CjT0tzBuH3VB71DjEwcjIcYJTiYlUR4Vbu0UoR4UxIrq1KL8uOLSnNSiw8x SnOwKInzXug6GS8kkJ5YkpqdmlqQWgSTZeLglGpgOr85pdlW933srugz9p81V1jdWKUs2VcY rXXLzqXmsthMw66FX52mcL0tCP16ROByy6qzIs17/7gG8G46a+lySTXqj6TUfV+eRP0b3sYC LmcPvNrv+vxymaJn49LCi4zX1gk27zeeMjGrxv67gZnkIYcDms8vMq570iYzReHvYpslDL5m /PsNtXp/RX8t+VjhmPY6es78ZackpczueWpfTGePePGK6WSlQm/4ljf7zrEddr9ZKBu7uGK3 ScynIGGjl2dFBZ9P33bw7t+7Abdapj3JMy7ZPkvv5wZN7rzq224dRe5ZmoKJTo036t8r3MtL bj70S1+e+xRvmrlc8bUz+qxVChkX4qee3fx6+brJSizFGYmGWsxFxYkAdCGC9CEDAAA= X-CMS-MailID: 20230404111937epcas2p25ae33c66401ba055e7d0478b945e9ffd X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20230404061409epcas2p15750d5844aa8d3655d1bfd094fac14a9 References: <20230404060011.108561-1-jaewon02.kim@samsung.com> <20230404060011.108561-2-jaewon02.kim@samsung.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Mark, On 23. 4. 4. 19:54, Mark Brown wrote: > On Tue, Apr 04, 2023 at 03:00:09PM +0900, Jaewon Kim wrote: >> This patch adds new 'samsung,spi-polling' property to support polling mode. >> In some environments, polling mode is required even if DMA is supported. >> Changed it to support not only with quick but also optinally with >> devicetree. > Why would this be required if we can use DMA? If this is a performance > optimisation for small messages the driver should just work out when to > choose PIO over DMA like other drivers do. It is hard to see this as a > hardware property which should be configured via DT. We are providing a VM environment in which several Guest OSs are running. If Host OS has DMA, GuestOS should use SPI as polling mode. In order to support s3c64xx in a DMA-less environment, it must be separated with a quirk. However, there is DMA in the Host OS and no DMA in the Guest OS, it is not correct to separate them with quirk. I'm considering supporting this systems with DeviceTree rather than qurik. If 'samsung,spi-polling' looks to be a SW configuration, how about 'samsung,no-dma'. This is not to simply change the mode using DeviceTree, but to support an environment without DMA. Thanks Jaewon Kim