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author | Hans de Goede <hdegoede@redhat.com> | 2020-05-12 14:00:44 +0300 |
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committer | Thierry Reding <thierry.reding@gmail.com> | 2020-06-02 15:21:42 +0300 |
commit | 01aa905d4791da7d3630f6030ff99d58105cca00 (patch) | |
tree | d545adebce7eb37362407d9e27ad1af85aaa54c5 /drivers/pwm/Kconfig | |
parent | 856c45d8c1a733e10ad82be817202eb32ea4e570 (diff) | |
download | linux-01aa905d4791da7d3630f6030ff99d58105cca00.tar.xz |
pwm: lpss: Fix get_state runtime-pm reference handling
Before commit cfc4c189bc70 ("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: cfc4c189bc70 ("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>
Diffstat (limited to 'drivers/pwm/Kconfig')
0 files changed, 0 insertions, 0 deletions