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Before commitcfc4c189bc("pwm: Read initial hardware state at request time"), a driver's get_state callback would get called once per PWM from pwmchip_add(). pwm-lpss' runtime-pm code was relying on this, getting a runtime-pm ref for PWMs which are enabled at probe time from within its get_state callback, before enabling runtime-pm. The change to calling get_state at request time causes a number of problems: 1. PWMs enabled at probe time may get runtime suspended before they are requested, causing e.g. a LCD backlight controlled by the PWM to turn off. 2. When the request happens when the PWM has been runtime suspended, the ctrl register will read all 1 / 0xffffffff, causing get_state to store bogus values in the pwm_state. 3. get_state was using an async pm_runtime_get() call, because it assumed that runtime-pm has not been enabled yet. If shortly after the request an apply call is made, then the pwm_lpss_is_updating() check may trigger because the resume triggered by the pm_runtime_get() call is not complete yet, so the ctrl register still reads all 1 / 0xffffffff. This commit fixes these issues by moving the initial pm_runtime_get() call for PWMs which are enabled at probe time to the pwm_lpss_probe() function; and by making get_state take a runtime-pm ref before reading the ctrl reg. BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1828927 Fixes:cfc4c189bc("pwm: Read initial hardware state at request time") Cc: stable@vger.kernel.org Signed-off-by: Hans de Goede <hdegoede@redhat.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Linux kernel
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