diff mbox series

[v2,2/2] drivers: thermal: tsens: add timeout to get_tem_tsens_valid

Message ID 20210907212543.20220-2-ansuelsmth@gmail.com (mailing list archive)
State Not Applicable
Headers show
Series [v2,1/2] drivers: thermal: tsens: fix wrong check for tzd in irq handlers | expand

Commit Message

Christian Marangi Sept. 7, 2021, 9:25 p.m. UTC 
The function can loop and lock the system if for whatever reason the bit
for the target sensor is NEVER valid. This is the case if a sensor is
disabled by the factory and the valid bit is never reported as actually
valid. Add a timeout check and exit if a timeout occurs. As this is
a very rare condition, handle the timeout only if the first read fails.
While at it also rework the function to improve readability.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 drivers/thermal/qcom/tsens.c | 40 +++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 14 deletions(-)

Comments

Matthias Kaehlcke Sept. 7, 2021, 9:57 p.m. UTC | #1 
On Tue, Sep 07, 2021 at 11:25:43PM +0200, Ansuel Smith wrote:
> The function can loop and lock the system if for whatever reason the bit
> for the target sensor is NEVER valid. This is the case if a sensor is
> disabled by the factory and the valid bit is never reported as actually
> valid. Add a timeout check and exit if a timeout occurs. As this is
> a very rare condition, handle the timeout only if the first read fails.
> While at it also rework the function to improve readability.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> ---
>  drivers/thermal/qcom/tsens.c | 40 +++++++++++++++++++++++-------------
>  1 file changed, 26 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c
> index b1162e566a70..1ff244176beb 100644
> --- a/drivers/thermal/qcom/tsens.c
> +++ b/drivers/thermal/qcom/tsens.c
> @@ -599,26 +599,38 @@ int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp)
>  	int hw_id = s->hw_id;
>  	u32 temp_idx = LAST_TEMP_0 + hw_id;
>  	u32 valid_idx = VALID_0 + hw_id;
> +	unsigned long timeout;
>  	u32 valid;
>  	int ret;
>  
>  	/* VER_0 doesn't have VALID bit */
> -	if (tsens_version(priv) >= VER_0_1) {
> +	if (tsens_version(priv) == VER_0)
> +		goto get_temp;
> +
> +	ret = regmap_field_read(priv->rf[valid_idx], &valid);
> +	if (ret || valid)
> +		goto check_valid;
> +
> +	timeout = jiffies + msecs_to_jiffies(20);
> +	do {
> +		/* Valid bit is 0 for 6 AHB clock cycles.
> +		 * At 19.2MHz, 1 AHB clock is ~60ns.
> +		 * We should enter this loop very, very rarely.
> +		 */
> +		ndelay(400);
>  		ret = regmap_field_read(priv->rf[valid_idx], &valid);
> -		if (ret)
> -			return ret;
> -		while (!valid) {
> -			/* Valid bit is 0 for 6 AHB clock cycles.
> -			 * At 19.2MHz, 1 AHB clock is ~60ns.
> -			 * We should enter this loop very, very rarely.
> -			 */
> -			ndelay(400);
> -			ret = regmap_field_read(priv->rf[valid_idx], &valid);
> -			if (ret)
> -				return ret;
> -		}
> -	}
> +		if (ret || valid)
> +			goto check_valid;
> +	} while (time_before(jiffies, timeout));
> +
> +	return -ETIMEDOUT;
> +
> +check_valid:
> +	/* Check ret of valid bit read */
> +	if (ret)
> +		return ret;
>  
> +get_temp:
>  	/* Valid bit is set, OK to read the temperature */
>  	*temp = tsens_hw_to_mC(s, temp_idx);

I still think that something like this would be clearer than the
multiple jumps to 'check_valid':


	ret = regmap_field_read(priv->rf[valid_idx], &valid);
	if (ret)
		return ret;

	timeout = jiffies + msecs_to_jiffies(20);

	while (!valid) {
		/* Valid bit is 0 for 6 AHB clock cycles.
		 * At 19.2MHz, 1 AHB clock is ~60ns.
		 * We should enter this loop very, very rarely.
		 */
		ndelay(400);
		ret = regmap_field_read(priv->rf[valid_idx], &valid);
		if (ret)
			return ret;

		if (time_after(jiffies, timeout))
			return -ETIMEDOUT;
	};

That said, I'm just a random dude, so my opinion isn't really important,
as long as the maintainers are happy with the change :)
Daniel Lezcano Sept. 17, 2021, 9:08 a.m. UTC | #2 
On 07/09/2021 23:25, Ansuel Smith wrote:
> The function can loop and lock the system if for whatever reason the bit
> for the target sensor is NEVER valid. This is the case if a sensor is
> disabled by the factory and the valid bit is never reported as actually
> valid. Add a timeout check and exit if a timeout occurs. As this is
> a very rare condition, handle the timeout only if the first read fails.
> While at it also rework the function to improve readability.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> ---
>  drivers/thermal/qcom/tsens.c | 40 +++++++++++++++++++++++-------------
>  1 file changed, 26 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c
> index b1162e566a70..1ff244176beb 100644
> --- a/drivers/thermal/qcom/tsens.c
> +++ b/drivers/thermal/qcom/tsens.c
> @@ -599,26 +599,38 @@ int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp)
>  	int hw_id = s->hw_id;
>  	u32 temp_idx = LAST_TEMP_0 + hw_id;
>  	u32 valid_idx = VALID_0 + hw_id;
> +	unsigned long timeout;
>  	u32 valid;
>  	int ret;
>  
>  	/* VER_0 doesn't have VALID bit */
> -	if (tsens_version(priv) >= VER_0_1) {
> +	if (tsens_version(priv) == VER_0)
> +		goto get_temp;
> +
> +	ret = regmap_field_read(priv->rf[valid_idx], &valid);
> +	if (ret || valid)
> +		goto check_valid;
> +
> +	timeout = jiffies + msecs_to_jiffies(20);

Why not use regmap_field_read_poll_timeout() ?

> +	do {
> +		/* Valid bit is 0 for 6 AHB clock cycles.
> +		 * At 19.2MHz, 1 AHB clock is ~60ns.
> +		 * We should enter this loop very, very rarely.
> +		 */
> +		ndelay(400);
>  		ret = regmap_field_read(priv->rf[valid_idx], &valid);
> -		if (ret)
> -			return ret;
> -		while (!valid) {
> -			/* Valid bit is 0 for 6 AHB clock cycles.
> -			 * At 19.2MHz, 1 AHB clock is ~60ns.
> -			 * We should enter this loop very, very rarely.
> -			 */
> -			ndelay(400);
> -			ret = regmap_field_read(priv->rf[valid_idx], &valid);
> -			if (ret)
> -				return ret;
> -		}
> -	}
> +		if (ret || valid)
> +			goto check_valid;
> +	} while (time_before(jiffies, timeout));
> +
> +	return -ETIMEDOUT;
> +
> +check_valid:
> +	/* Check ret of valid bit read */
> +	if (ret)
> +		return ret;
>  
> +get_temp:
>  	/* Valid bit is set, OK to read the temperature */
>  	*temp = tsens_hw_to_mC(s, temp_idx);
>  
>
Christian Marangi Sept. 17, 2021, 11:06 a.m. UTC | #3 
On Fri, Sep 17, 2021 at 11:08:15AM +0200, Daniel Lezcano wrote:
> On 07/09/2021 23:25, Ansuel Smith wrote:
> > The function can loop and lock the system if for whatever reason the bit
> > for the target sensor is NEVER valid. This is the case if a sensor is
> > disabled by the factory and the valid bit is never reported as actually
> > valid. Add a timeout check and exit if a timeout occurs. As this is
> > a very rare condition, handle the timeout only if the first read fails.
> > While at it also rework the function to improve readability.
> > 
> > Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> > ---
> >  drivers/thermal/qcom/tsens.c | 40 +++++++++++++++++++++++-------------
> >  1 file changed, 26 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c
> > index b1162e566a70..1ff244176beb 100644
> > --- a/drivers/thermal/qcom/tsens.c
> > +++ b/drivers/thermal/qcom/tsens.c
> > @@ -599,26 +599,38 @@ int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp)
> >  	int hw_id = s->hw_id;
> >  	u32 temp_idx = LAST_TEMP_0 + hw_id;
> >  	u32 valid_idx = VALID_0 + hw_id;
> > +	unsigned long timeout;
> >  	u32 valid;
> >  	int ret;
> >  
> >  	/* VER_0 doesn't have VALID bit */
> > -	if (tsens_version(priv) >= VER_0_1) {
> > +	if (tsens_version(priv) == VER_0)
> > +		goto get_temp;
> > +
> > +	ret = regmap_field_read(priv->rf[valid_idx], &valid);
> > +	if (ret || valid)
> > +		goto check_valid;
> > +
> > +	timeout = jiffies + msecs_to_jiffies(20);
> 
> Why not use regmap_field_read_poll_timeout() ?
>

Ok will convert this to pool_timeout and send v3.
Thx for the review.

> > +	do {
> > +		/* Valid bit is 0 for 6 AHB clock cycles.
> > +		 * At 19.2MHz, 1 AHB clock is ~60ns.
> > +		 * We should enter this loop very, very rarely.
> > +		 */
> > +		ndelay(400);
> >  		ret = regmap_field_read(priv->rf[valid_idx], &valid);
> > -		if (ret)
> > -			return ret;
> > -		while (!valid) {
> > -			/* Valid bit is 0 for 6 AHB clock cycles.
> > -			 * At 19.2MHz, 1 AHB clock is ~60ns.
> > -			 * We should enter this loop very, very rarely.
> > -			 */
> > -			ndelay(400);
> > -			ret = regmap_field_read(priv->rf[valid_idx], &valid);
> > -			if (ret)
> > -				return ret;
> > -		}
> > -	}
> > +		if (ret || valid)
> > +			goto check_valid;
> > +	} while (time_before(jiffies, timeout));
> > +
> > +	return -ETIMEDOUT;
> > +
> > +check_valid:
> > +	/* Check ret of valid bit read */
> > +	if (ret)
> > +		return ret;
> >  
> > +get_temp:
> >  	/* Valid bit is set, OK to read the temperature */
> >  	*temp = tsens_hw_to_mC(s, temp_idx);
> >  
> > 
> 
> 
> -- 
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> 
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diff mbox series

Patch

diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c
index b1162e566a70..1ff244176beb 100644
--- a/drivers/thermal/qcom/tsens.c
+++ b/drivers/thermal/qcom/tsens.c
@@ -599,26 +599,38 @@  int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp)
 	int hw_id = s->hw_id;
 	u32 temp_idx = LAST_TEMP_0 + hw_id;
 	u32 valid_idx = VALID_0 + hw_id;
+	unsigned long timeout;
 	u32 valid;
 	int ret;
 
 	/* VER_0 doesn't have VALID bit */
-	if (tsens_version(priv) >= VER_0_1) {
+	if (tsens_version(priv) == VER_0)
+		goto get_temp;
+
+	ret = regmap_field_read(priv->rf[valid_idx], &valid);
+	if (ret || valid)
+		goto check_valid;
+
+	timeout = jiffies + msecs_to_jiffies(20);
+	do {
+		/* Valid bit is 0 for 6 AHB clock cycles.
+		 * At 19.2MHz, 1 AHB clock is ~60ns.
+		 * We should enter this loop very, very rarely.
+		 */
+		ndelay(400);
 		ret = regmap_field_read(priv->rf[valid_idx], &valid);
-		if (ret)
-			return ret;
-		while (!valid) {
-			/* Valid bit is 0 for 6 AHB clock cycles.
-			 * At 19.2MHz, 1 AHB clock is ~60ns.
-			 * We should enter this loop very, very rarely.
-			 */
-			ndelay(400);
-			ret = regmap_field_read(priv->rf[valid_idx], &valid);
-			if (ret)
-				return ret;
-		}
-	}
+		if (ret || valid)
+			goto check_valid;
+	} while (time_before(jiffies, timeout));
+
+	return -ETIMEDOUT;
+
+check_valid:
+	/* Check ret of valid bit read */
+	if (ret)
+		return ret;
 
+get_temp:
 	/* Valid bit is set, OK to read the temperature */
 	*temp = tsens_hw_to_mC(s, temp_idx);