| Message ID | 20200512110044.95984-1-hdegoede@redhat.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | pwm: lpss: Fix get_state runtime-pm reference handling | expand |
On Tue, May 12, 2020 at 01:00:44PM +0200, Hans de Goede wrote: > 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. Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> One thing to consider below. > 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> > --- > drivers/pwm/pwm-lpss.c | 15 +++++++++++---- > 1 file 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) I would create a helper for this as opposite to pwm_lpss_cond_enable(), something like pwm_lpss_is_enabled(). > + pm_runtime_get(dev); > + } > + > return lpwm; > } > EXPORT_SYMBOL_GPL(pwm_lpss_probe); > -- > 2.26.0 >
Hi, On 5/12/20 9:01 PM, Andy Shevchenko wrote: > On Tue, May 12, 2020 at 01:00:44PM +0200, Hans de Goede wrote: >> 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. > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Thank you. > One thing to consider below. > >> 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> >> --- >> drivers/pwm/pwm-lpss.c | 15 +++++++++++---- >> 1 file 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) > > I would create a helper for this as opposite to pwm_lpss_cond_enable(), > something like pwm_lpss_is_enabled(). pwm_lpss_cond_enable() is used in multiple places, this check we only need once, so I would prefer to just keep it as is. Regards, Hans > >> + pm_runtime_get(dev); >> + } >> + >> return lpwm; >> } >> EXPORT_SYMBOL_GPL(pwm_lpss_probe); >> -- >> 2.26.0 >> >
On Tue, May 12, 2020 at 01:00:44PM +0200, Hans de Goede wrote: > 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> > --- > drivers/pwm/pwm-lpss.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) Applied, thanks. Thierry
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);
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> --- drivers/pwm/pwm-lpss.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)