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Tue, 27 Jan 2026 18:53:13 -0800 (PST) Date: Tue, 27 Jan 2026 21:53:38 -0500 From: Richard Acayan To: Sakari Ailus Cc: Bryan O'Donoghue , Mauro Carvalho Chehab , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Tianshu Qiu , linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, Robert Mader , Vladimir Zapolskiy , David Heidelberg , phone-devel@vger.kernel.org Subject: Re: [PATCH v7 2/5] media: i2c: imx355: Support devicetree and power management Message-ID: References: <20260117040657.27043-1-mailingradian@gmail.com> <20260117040657.27043-3-mailingradian@gmail.com> <578668b0-cba2-4550-b676-26ed0b447bf2@linaro.org> Precedence: bulk X-Mailing-List: phone-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jan 20, 2026 at 04:49:21PM +0200, Sakari Ailus wrote: > Hi Bryan, others, > > On Tue, Jan 20, 2026 at 12:44:24PM +0000, Bryan O'Donoghue wrote: > > I think reset should be asserted before regulators and power are switched > > on. i.e. before you try to switch the chip on, you should establish that the > > reset pin is in the state that the timing diagram calls for. > > Indeed. I think the discussion is more about whether there should be an assert in the same function as the de-assert. > The xshutdown pin, as it is typically called labelled as "reset" in this > case, functions as both hardware reset and hardware standby mode control. > It should be asserted (i.e. be set to low level) whenever the sensor is > expected to be powered off. Typically deasserting it is the last step in > the sensor's power-up sequence. This applies to nearly all CSI-2 and DVP > (parallel) camera sensors. (There are some exceptions that use explicitly > two GPIOs for similar functions but there are very few of them.) This patch has the reset asserted by the time it gets to imx355_power_on(): - when coming from runtime PM, the suspend callback asserted it - when coming from probe, GPIOD_OUT_HIGH asserted it (considering that active-low also affects the initial output setting) Should it be asserted again inside the function, or should the initial `gpiod_set_value_cansleep()` be removed?