Re: [PATCH v2] iio: trigger: stm32-timer-trigger: Add check for clk_enable()

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 11 Nov 2024 14:15:43 -0500
Jiasheng Jiang <jiashengjiangcool@gmail.com> wrote:

> On Sat, Nov 9, 2024 at 8:38 AM Jonathan Cameron <jic23@kernel.org> wrote:
> >
> > On Fri,  8 Nov 2024 20:09:00 +0000
> > Jiasheng Jiang <jiashengjiangcool@gmail.com> wrote:
> >  
> > > Add check for the return value of clk_enable() in order to catch the
> > > potential exception.
> > >
> > > Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>  
> > Hi,
> >
> > In principle this is fine, but I'd rather we made use of guard()
> > / scoped_guard() rather than adding the explicit unlocks.
> >
> > If you do that as a precursor patch in appropriate places
> > in the driver then this will be a little cleaner.
> >
> > Note I'll not be taking this until next cycle now anyway.
> >
> > Jonathan
> >  
> > > ---
> > > Changelog:
> > >
> > > v1 -> v2:
> > >
> > > 1. Remove unsuitable dev_err_probe().
> > > ---
> > >  drivers/iio/trigger/stm32-timer-trigger.c | 32 ++++++++++++++++++-----
> > >  1 file changed, 25 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c
> > > index 0684329956d9..e1e077122f73 100644
> > > --- a/drivers/iio/trigger/stm32-timer-trigger.c
> > > +++ b/drivers/iio/trigger/stm32-timer-trigger.c
> > > @@ -119,7 +119,7 @@ static int stm32_timer_start(struct stm32_timer_trigger *priv,
> > >                            unsigned int frequency)
> > >  {
> > >       unsigned long long prd, div;
> > > -     int prescaler = 0;
> > > +     int prescaler = 0, ret;
> > >       u32 ccer;
> > >
> > >       /* Period and prescaler values depends of clock rate */
> > > @@ -153,7 +153,11 @@ static int stm32_timer_start(struct stm32_timer_trigger *priv,
> > >       mutex_lock(&priv->lock);
> > >       if (!priv->enabled) {
> > >               priv->enabled = true;
> > > -             clk_enable(priv->clk);
> > > +             ret = clk_enable(priv->clk);
> > > +             if (ret) {
> > > +                     mutex_unlock(&priv->lock);  
> >
> > as below guard() for when the mutex is locked is cleaner.
> >  
> > > +                     return ret;
> > > +             }
> > >       }
> > >
> > >       regmap_write(priv->regmap, TIM_PSC, prescaler);
> > > @@ -307,7 +311,7 @@ static ssize_t stm32_tt_store_master_mode(struct device *dev,
> > >       struct stm32_timer_trigger *priv = dev_get_drvdata(dev);
> > >       struct iio_trigger *trig = to_iio_trigger(dev);
> > >       u32 mask, shift, master_mode_max;
> > > -     int i;
> > > +     int i, ret;
> > >
> > >       if (stm32_timer_is_trgo2_name(trig->name)) {
> > >               mask = TIM_CR2_MMS2;
> > > @@ -326,7 +330,11 @@ static ssize_t stm32_tt_store_master_mode(struct device *dev,
> > >                       if (!priv->enabled) {
> > >                               /* Clock should be enabled first */
> > >                               priv->enabled = true;
> > > -                             clk_enable(priv->clk);
> > > +                             ret = clk_enable(priv->clk);
> > > +                             if (ret) {
> > > +                                     mutex_unlock(&priv->lock);  
> > As below. Prefer use of guard() so we don't have to handle the unlock manually.  
> > > +                                     return ret;
> > > +                             }
> > >                       }
> > >                       regmap_update_bits(priv->regmap, TIM_CR2, mask,
> > >                                          i << shift);
> > > @@ -482,6 +490,7 @@ static int stm32_counter_write_raw(struct iio_dev *indio_dev,
> > >                                  int val, int val2, long mask)
> > >  {
> > >       struct stm32_timer_trigger *priv = iio_priv(indio_dev);
> > > +     int ret;
> > >
> > >       switch (mask) {
> > >       case IIO_CHAN_INFO_RAW:
> > > @@ -496,7 +505,11 @@ static int stm32_counter_write_raw(struct iio_dev *indio_dev,
> > >               if (val) {
> > >                       if (!priv->enabled) {
> > >                               priv->enabled = true;
> > > -                             clk_enable(priv->clk);
> > > +                             ret = clk_enable(priv->clk);
> > > +                             if (ret) {
> > > +                                     mutex_unlock(&priv->lock);  
> > Add include of cleanup.h and swithch the place where the mutex is locked to
> > guard(mutex)(&priv->lock);
> > then remember to drop the explicit unlocks.  
> 
> I found that cleanup.h is already included.
> 
> Moreover, since labels cannot be followed by declarations,
> I encountered a compilation error when using guard().
> Therefore, I switched to using scoped_guard().
Sometimes it is better to just add scope for blocks in switch statement
with 
case XXX: {
	guard()
}
because then we don't get the extra indent a scoped_guard() requires.

I'll take a look at the result in this case though!

Jonathan

> >  
> > > +                                     return ret;
> > > +                             }
> > >                       }
> > >                       regmap_set_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN);
> > >               } else {
> > > @@ -601,7 +614,7 @@ static int stm32_set_enable_mode(struct iio_dev *indio_dev,
> > >                                unsigned int mode)
> > >  {
> > >       struct stm32_timer_trigger *priv = iio_priv(indio_dev);
> > > -     int sms = stm32_enable_mode2sms(mode);
> > > +     int sms = stm32_enable_mode2sms(mode), ret;
> > >
> > >       if (sms < 0)
> > >               return sms;
> > > @@ -611,7 +624,12 @@ static int stm32_set_enable_mode(struct iio_dev *indio_dev,
> > >        */
> > >       mutex_lock(&priv->lock);  
> >
> > Perhaps scoped_guard() is  appropriate here.
> >  
> > >       if (sms == 6 && !priv->enabled) {
> > > -             clk_enable(priv->clk);
> > > +             ret = clk_enable(priv->clk);
> > > +             if (ret) {
> > > +                     mutex_unlock(&priv->lock);
> > > +                     return ret;
> > > +             }
> > > +
> > >               priv->enabled = true;
> > >       }
> > >       mutex_unlock(&priv->lock);  
> >  
> 
> Thanks, I will submit a v2 to simplify code with cleanup helpers.
> 
> -Jiasheng