2020年1月9日(木) 1:13 Rob Herring <robh@xxxxxxxxxx>: > > On Sun, Dec 22, 2019 at 11:10:22PM +0900, Akinobu Mita wrote: > > The pwm-fan driver leaves the fun running when shutting down the system. > > (On the other hand the gpio-fan driver stops it.) > > Seemms like we should have consistent behavior independent of what the > underlying implementation uses. Is there actually a case you'd want to > leave the fan on? It seems strange to disable in suspend and leave on in > shutdown. I agree. I was trying to keep the current behavior unchanged, so I added "disable-state-shutdown" property. But I can't think of any case we want to leave the fun on in shutdown. So it's better to change the shutdown behavior and remove the option completely or add "retain-state-shutdown" property instead. (The "retain-state-shutdown" property is inspired by gpio-leds) > Wouldn't the shutdown state depend if the PWM off state is high or low? > IIRC, i.MX PWM has a quirk that the PWM disabled state is high. Doesn't It could be possible to affect the shutdown behavior for pwm-fan. There are three i.MX PWM drivers (pwm-imx1, pwm-imx27, and pwm-tpm). Do you remember which one actually have such limitation? Maybe it should be handled by the PWM controller/chip driver and PWM core. >From the perspective of PWM user drivers for now, we have nothing to do other than setting duty cycle zero and then disable PWM for stopping the pwm-fan. > it also depend on what the PWM driver does in shutdown? I think so. But as far as I can see, no PWM drivers implement shutdown callback.
