The ARR (auto reload register) and CMP (compare) registers are
successively written. The status bits to check the update of these
registers are polled together with regmap_read_poll_timeout().
The condition to end the loop may become true, even if one of the register
isn't correctly updated.
So ensure both status bits are set before clearing them.
Fixes: d8958824cf07 ("iio: counter: Add support for STM32 LPTimer")
Signed-off-by: Fabrice Gasnier <[email protected]>
---
drivers/counter/stm32-lptimer-cnt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
index d6b80b6dfc28..8439755559b2 100644
--- a/drivers/counter/stm32-lptimer-cnt.c
+++ b/drivers/counter/stm32-lptimer-cnt.c
@@ -69,7 +69,7 @@ static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
/* ensure CMP & ARR registers are properly written */
ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
- (val & STM32_LPTIM_CMPOK_ARROK),
+ (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
100, 1000);
if (ret)
return ret;
--
2.25.1
On Wed, Nov 23, 2022 at 02:36:09PM +0100, Fabrice Gasnier wrote:
> The ARR (auto reload register) and CMP (compare) registers are
> successively written. The status bits to check the update of these
> registers are polled together with regmap_read_poll_timeout().
> The condition to end the loop may become true, even if one of the register
> isn't correctly updated.
> So ensure both status bits are set before clearing them.
>
> Fixes: d8958824cf07 ("iio: counter: Add support for STM32 LPTimer")
> Signed-off-by: Fabrice Gasnier <[email protected]>
> ---
> drivers/counter/stm32-lptimer-cnt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
> index d6b80b6dfc28..8439755559b2 100644
> --- a/drivers/counter/stm32-lptimer-cnt.c
> +++ b/drivers/counter/stm32-lptimer-cnt.c
> @@ -69,7 +69,7 @@ static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
>
> /* ensure CMP & ARR registers are properly written */
> ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
> - (val & STM32_LPTIM_CMPOK_ARROK),
> + (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
This is a reasonable fix, but I don't like seeing so much happening in
an argument list -- it's easy to misunderstand what's going on which can
lead to further bugs the future. Pull out this condition to a dedicated
bool variable with a comment explaining why we need the equivalence
check (i.e. to ensure both status bits are set and not just one).
William Breathitt Gray
On Tue, Nov 22, 2022 at 02:27:50AM -0500, William Breathitt Gray wrote:
> On Wed, Nov 23, 2022 at 02:36:09PM +0100, Fabrice Gasnier wrote:
> > The ARR (auto reload register) and CMP (compare) registers are
> > successively written. The status bits to check the update of these
> > registers are polled together with regmap_read_poll_timeout().
> > The condition to end the loop may become true, even if one of the register
> > isn't correctly updated.
> > So ensure both status bits are set before clearing them.
> >
> > Fixes: d8958824cf07 ("iio: counter: Add support for STM32 LPTimer")
> > Signed-off-by: Fabrice Gasnier <[email protected]>
> > ---
> > drivers/counter/stm32-lptimer-cnt.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
> > index d6b80b6dfc28..8439755559b2 100644
> > --- a/drivers/counter/stm32-lptimer-cnt.c
> > +++ b/drivers/counter/stm32-lptimer-cnt.c
> > @@ -69,7 +69,7 @@ static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
> >
> > /* ensure CMP & ARR registers are properly written */
> > ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
> > - (val & STM32_LPTIM_CMPOK_ARROK),
> > + (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
>
> This is a reasonable fix, but I don't like seeing so much happening in
> an argument list -- it's easy to misunderstand what's going on which can
> lead to further bugs the future. Pull out this condition to a dedicated
> bool variable with a comment explaining why we need the equivalence
> check (i.e. to ensure both status bits are set and not just one).
>
> William Breathitt Gray
Alternatively, you could pull out just (val & STM32_LPTIM_CMPOK_ARROK)
to a separate variable and keep the equivalence condition inline if you
think it'll be clearer that way.
William Breathitt Gray
On Wed, Nov 23, 2022 at 03:56:31PM +0100, Fabrice Gasnier wrote:
> On 11/22/22 08:33, William Breathitt Gray wrote:
> > On Tue, Nov 22, 2022 at 02:27:50AM -0500, William Breathitt Gray wrote:
> >> On Wed, Nov 23, 2022 at 02:36:09PM +0100, Fabrice Gasnier wrote:
> >>> The ARR (auto reload register) and CMP (compare) registers are
> >>> successively written. The status bits to check the update of these
> >>> registers are polled together with regmap_read_poll_timeout().
> >>> The condition to end the loop may become true, even if one of the register
> >>> isn't correctly updated.
> >>> So ensure both status bits are set before clearing them.
> >>>
> >>> Fixes: d8958824cf07 ("iio: counter: Add support for STM32 LPTimer")
> >>> Signed-off-by: Fabrice Gasnier <[email protected]>
> >>> ---
> >>> drivers/counter/stm32-lptimer-cnt.c | 2 +-
> >>> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
> >>> index d6b80b6dfc28..8439755559b2 100644
> >>> --- a/drivers/counter/stm32-lptimer-cnt.c
> >>> +++ b/drivers/counter/stm32-lptimer-cnt.c
> >>> @@ -69,7 +69,7 @@ static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
> >>>
> >>> /* ensure CMP & ARR registers are properly written */
> >>> ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
> >>> - (val & STM32_LPTIM_CMPOK_ARROK),
> >>> + (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
> >>
> >> This is a reasonable fix, but I don't like seeing so much happening in
> >> an argument list -- it's easy to misunderstand what's going on which can
> >> lead to further bugs the future. Pull out this condition to a dedicated
> >> bool variable with a comment explaining why we need the equivalence
> >> check (i.e. to ensure both status bits are set and not just one).
> >>
> >> William Breathitt Gray
> >
> > Alternatively, you could pull out just (val & STM32_LPTIM_CMPOK_ARROK)
> > to a separate variable and keep the equivalence condition inline if you
> > think it'll be clearer that way.
>
> Hi William,
>
> I'm not sure to fully understand your proposal here.
> Could you clarify ?
>
> regmap_read_poll_timeout() macro requires:
>
> * @val: Unsigned integer variable to read the value into
> * @cond: Break condition (usually involving @val)
>
> So do you wish I introduce a macro that abstracts the condition check ?
> (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK
>
>
> Best regards,
> Fabrice
My apologies Fabrice, I realize now that regmap_read_poll_timeout() is a
macro. Abstracting out the conditional would probably be more confusing
than having it inline, so the way it is right now is probably fine after
all.
William Breathitt Gray
On 11/22/22 08:33, William Breathitt Gray wrote:
> On Tue, Nov 22, 2022 at 02:27:50AM -0500, William Breathitt Gray wrote:
>> On Wed, Nov 23, 2022 at 02:36:09PM +0100, Fabrice Gasnier wrote:
>>> The ARR (auto reload register) and CMP (compare) registers are
>>> successively written. The status bits to check the update of these
>>> registers are polled together with regmap_read_poll_timeout().
>>> The condition to end the loop may become true, even if one of the register
>>> isn't correctly updated.
>>> So ensure both status bits are set before clearing them.
>>>
>>> Fixes: d8958824cf07 ("iio: counter: Add support for STM32 LPTimer")
>>> Signed-off-by: Fabrice Gasnier <[email protected]>
>>> ---
>>> drivers/counter/stm32-lptimer-cnt.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
>>> index d6b80b6dfc28..8439755559b2 100644
>>> --- a/drivers/counter/stm32-lptimer-cnt.c
>>> +++ b/drivers/counter/stm32-lptimer-cnt.c
>>> @@ -69,7 +69,7 @@ static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
>>>
>>> /* ensure CMP & ARR registers are properly written */
>>> ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
>>> - (val & STM32_LPTIM_CMPOK_ARROK),
>>> + (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
>>
>> This is a reasonable fix, but I don't like seeing so much happening in
>> an argument list -- it's easy to misunderstand what's going on which can
>> lead to further bugs the future. Pull out this condition to a dedicated
>> bool variable with a comment explaining why we need the equivalence
>> check (i.e. to ensure both status bits are set and not just one).
>>
>> William Breathitt Gray
>
> Alternatively, you could pull out just (val & STM32_LPTIM_CMPOK_ARROK)
> to a separate variable and keep the equivalence condition inline if you
> think it'll be clearer that way.
Hi William,
I'm not sure to fully understand your proposal here.
Could you clarify ?
regmap_read_poll_timeout() macro requires:
* @val: Unsigned integer variable to read the value into
* @cond: Break condition (usually involving @val)
So do you wish I introduce a macro that abstracts the condition check ?
(val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK
Best regards,
Fabrice
>
> William Breathitt Gray
On Wed, Nov 23, 2022 at 02:36:09PM +0100, Fabrice Gasnier wrote:
> The ARR (auto reload register) and CMP (compare) registers are
> successively written. The status bits to check the update of these
> registers are polled together with regmap_read_poll_timeout().
> The condition to end the loop may become true, even if one of the register
> isn't correctly updated.
> So ensure both status bits are set before clearing them.
>
> Fixes: d8958824cf07 ("iio: counter: Add support for STM32 LPTimer")
> Signed-off-by: Fabrice Gasnier <[email protected]>
Applied to the counter-current branch of counter.git.
William Breathitt Gray
> ---
> drivers/counter/stm32-lptimer-cnt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
> index d6b80b6dfc28..8439755559b2 100644
> --- a/drivers/counter/stm32-lptimer-cnt.c
> +++ b/drivers/counter/stm32-lptimer-cnt.c
> @@ -69,7 +69,7 @@ static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
>
> /* ensure CMP & ARR registers are properly written */
> ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
> - (val & STM32_LPTIM_CMPOK_ARROK),
> + (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
> 100, 1000);
> if (ret)
> return ret;
> --
> 2.25.1
>