linux-kernel - Re: [PATCH v2] iio: trigger: stm32-timer-trigger: Add check for clk

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Message-ID: <20241109133846.53d7ef06@jic23-huawei>
Date: Sat, 9 Nov 2024 13:38:46 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Jiasheng Jiang <jiashengjiangcool@...il.com>
Cc: lars@...afoo.de, mcoquelin.stm32@...il.com,
 alexandre.torgue@...s.st.com, u.kleine-koenig@...libre.com,
 tgamblin@...libre.com, fabrice.gasnier@...com,
 benjamin.gaignard@...aro.org, lee@...nel.org, linux-iio@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: trigger: stm32-timer-trigger: Add check for
 clk_enable()

On Fri,  8 Nov 2024 20:09:00 +0000
Jiasheng Jiang <jiashengjiangcool@...il.com> wrote:

> Add check for the return value of clk_enable() in order to catch the
> potential exception.
> 
> Signed-off-by: Jiasheng Jiang <jiashengjiangcool@...il.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.


> +					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);