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?
