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| author | Hans de Goede <hdegoede@redhat.com> | 2020-05-12 13:00:44 +0200 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2020-06-02 14:21:42 +0200 |
| commit | 01aa905d4791da7d3630f6030ff99d58105cca00 (patch) | |
| tree | d545adebce7eb37362407d9e27ad1af85aaa54c5 /drivers/pwm | |
| parent | 856c45d8c1a733e10ad82be817202eb32ea4e570 (diff) | |
| download | linux-01aa905d4791da7d3630f6030ff99d58105cca00.tar.bz2 | |
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')
| -rw-r--r-- | drivers/pwm/pwm-lpss.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 75bbfe5f3bc2..9d965ffe66d1 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -158,7 +158,6 @@ static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, return 0; } -/* This function gets called once from pwmchip_add to get the initial state */ static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm, struct pwm_state *state) { @@ -167,6 +166,8 @@ static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm, unsigned long long base_unit, freq, on_time_div; u32 ctrl; + pm_runtime_get_sync(chip->dev); + base_unit_range = BIT(lpwm->info->base_unit_bits); ctrl = pwm_lpss_read(pwm); @@ -187,8 +188,7 @@ static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm, state->polarity = PWM_POLARITY_NORMAL; state->enabled = !!(ctrl & PWM_ENABLE); - if (state->enabled) - pm_runtime_get(chip->dev); + pm_runtime_put(chip->dev); } static const struct pwm_ops pwm_lpss_ops = { @@ -202,7 +202,8 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r, { struct pwm_lpss_chip *lpwm; unsigned long c; - int ret; + int i, ret; + u32 ctrl; if (WARN_ON(info->npwm > MAX_PWMS)) return ERR_PTR(-ENODEV); @@ -232,6 +233,12 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r, return ERR_PTR(ret); } + for (i = 0; i < lpwm->info->npwm; i++) { + ctrl = pwm_lpss_read(&lpwm->chip.pwms[i]); + if (ctrl & PWM_ENABLE) + pm_runtime_get(dev); + } + return lpwm; } EXPORT_SYMBOL_GPL(pwm_lpss_probe); |