On 1/26/23 18:05, Maxime Ripard wrote: > On the RaspberryPi0-3, the HSM clock was provided by the clk-bcm2835 > driver, but on the Pi4 it was provided by the firmware through the > clk-raspberrypi driver. > > The clk-bcm2835 driver registers the HSM clock using the > CLK_SET_RATE_GATE flag that prevents any modification to the rate while > the clock is active. > > This meant that we needed to call clk_set_min_rate() before our call to > pm_runtime_resume_and_get() since our runtime_resume implementation > needs to enable the HSM clock for the HDMI controller registers to be > functional. > > However, the HSM clock is part of the HDMI power domain which might not > be powered prior to the pm_runtime_resume_and_get() call, so we could > end up changing the rate of the HSM clock while its power domain was > disabled. > > We recently changed the backing driver for the RaspberryPi0-3 to > clk-raspberrypi though, which doesn't have such restrictions. We can > thus move the clk_set_min_rate() after our call to runtime_resume and > avoid the access while the power domain is disabled. > > Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx> > --- I'm not familiar with the RPi clock hierarchy but the commit message explains why a clk_set_min_rate() was needed before the pm_runtime_resume_and_get(), and why that isn't needed anymore after the switch to clk-raspberrypi driver. And certainly, the correct thing to do is to enable the power domain that a controller is part of, before attempting to change the rate for one of its clocks. So the patch looks good to me. Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx> -- Best regards, Javier Martinez Canillas Core Platforms Red Hat
