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[88.156.142.67]) by smtp.gmail.com with ESMTPSA id m18-20020a194352000000b004b55ca53543sm2169721lfj.233.2022.12.08.00.46.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Dec 2022 00:46:28 -0800 (PST) Message-ID: Date: Thu, 8 Dec 2022 09:46:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2 7/9] dt-bindings: spi: mtk-snfi: Add read latch latency property Content-Language: en-US To: =?UTF-8?B?WGlhbmdzaGVuZyBIb3UgKOS+r+elpeiDnCk=?= , "miquel.raynal@bootlin.com" , "robh+dt@kernel.org" , "broonie@kernel.org" , "krzysztof.kozlowski+dt@linaro.org" , "matthias.bgg@gmail.com" , "gch981213@gmail.com" , "vigneshr@ti.com" , "angelogioacchino.delregno@collabora.com" , "richard@nod.at" Cc: "linux-kernel@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , "linux-mtd@lists.infradead.org" , "devicetree@vger.kernel.org" , =?UTF-8?B?QmVubGlhbmcgWmhhbyAo6LW15pys5LquKQ==?= , "linux-spi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , =?UTF-8?B?QmluIFpoYW5nICjnq6Dmlowp?= References: <20221205065756.26875-1-xiangsheng.hou@mediatek.com> <20221205065756.26875-8-xiangsheng.hou@mediatek.com> <9992c9a5-059a-9396-32ce-7ed63cd12a96@collabora.com> <97408c484927b6520ec79b23220496d628156e5f.camel@mediatek.com> From: Krzysztof Kozlowski In-Reply-To: <97408c484927b6520ec79b23220496d628156e5f.camel@mediatek.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org On 08/12/2022 02:15, Xiangsheng Hou (侯祥胜) wrote: >>> >>> There have two rx related timing properties in spi-peripheral- >>> props. >>> The rx-sample-delay-ns have been used in Mediatek snfi driver to >>> adjust >>> controller sample delay. >>> However another spi-rx-delay-us is in microseconds. Take 52MHz for >>> example, the clock cycle will be 19.23ns which lower than 1us. This >>> may >>> not easy to by one clock cycle. >>> >> >> I agree, but nothing prevents you from adding your own property for >> that. >> >> I propose "mediatek,rx-latch-latency-ns" or "mediatek,rx-latency-ns", >> so that >> we can specify the delay in nanoseconds: in that case, when we >> specify 19ns, >> the driver will safely round that resulting in 52MHz == 19.23ns => >> 19ns valid. > > Will be fixed in next series. I am fine with this approach, but after explanations I was also fine with clock cycles as unit. It's still quite specific unit and I think several timings on buses are clock-cycle dependent, not time dependent. Best regards, Krzysztof