* [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling
@ 2020-05-12 11:00 Hans de Goede
2020-05-12 19:01 ` Andy Shevchenko
2020-06-02 12:40 ` Thierry Reding
0 siblings, 2 replies; 4+ messages in thread
From: Hans de Goede @ 2020-05-12 11:00 UTC (permalink / raw)
To: Thierry Reding, Uwe Kleine-König
Cc: Hans de Goede, Andy Shevchenko, linux-pwm, linux-acpi, stable
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(-)
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);
--
2.26.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling
2020-05-12 11:00 [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling Hans de Goede
@ 2020-05-12 19:01 ` Andy Shevchenko
2020-05-12 20:39 ` Hans de Goede
2020-06-02 12:40 ` Thierry Reding
1 sibling, 1 reply; 4+ messages in thread
From: Andy Shevchenko @ 2020-05-12 19:01 UTC (permalink / raw)
To: Hans de Goede
Cc: Thierry Reding, Uwe Kleine-König, linux-pwm, linux-acpi, stable
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
>
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling
2020-05-12 19:01 ` Andy Shevchenko
@ 2020-05-12 20:39 ` Hans de Goede
0 siblings, 0 replies; 4+ messages in thread
From: Hans de Goede @ 2020-05-12 20:39 UTC (permalink / raw)
To: Andy Shevchenko
Cc: Thierry Reding, Uwe Kleine-König, linux-pwm, linux-acpi, stable
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
>>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling
2020-05-12 11:00 [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling Hans de Goede
2020-05-12 19:01 ` Andy Shevchenko
@ 2020-06-02 12:40 ` Thierry Reding
1 sibling, 0 replies; 4+ messages in thread
From: Thierry Reding @ 2020-06-02 12:40 UTC (permalink / raw)
To: Hans de Goede
Cc: Uwe Kleine-König, Andy Shevchenko, linux-pwm, linux-acpi, stable
[-- Attachment #1: Type: text/plain, Size: 1830 bytes --]
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
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2020-05-12 11:00 [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling Hans de Goede
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2020-06-02 12:40 ` Thierry Reding
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