| Message ID | 20210905174708.4605-2-ansuelsmth@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
On Sun, Sep 05, 2021 at 07:47:08PM +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. > > Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com> > --- > drivers/thermal/qcom/tsens.c | 23 ++++++++++++++++------- > 1 file changed, 16 insertions(+), 7 deletions(-) > > diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c > index b1162e566a70..38afde1a599f 100644 > --- a/drivers/thermal/qcom/tsens.c > +++ b/drivers/thermal/qcom/tsens.c > @@ -599,6 +599,7 @@ 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; > > @@ -607,13 +608,21 @@ int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp) > 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 (!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 (valid || ret) > + break; > + } while (!(ret = time_after_eq(jiffies, timeout))); > + > if (ret) > return ret; With the overloading of 'ret' the return logic is getting a bit more convoluted. Also the function should probably return -ETIMEDOUT or some other meaningful error if the bit is never valid. How about keeping the 'while (!valid)' condition, and adding if (time_after_eq(jiffies, timeout)) return -ETIMEDOUT; inside the loop?
On Tue, Sep 07, 2021 at 01:55:03PM -0700, Matthias Kaehlcke wrote: > On Sun, Sep 05, 2021 at 07:47:08PM +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. > > > > Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com> > > --- > > drivers/thermal/qcom/tsens.c | 23 ++++++++++++++++------- > > 1 file changed, 16 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c > > index b1162e566a70..38afde1a599f 100644 > > --- a/drivers/thermal/qcom/tsens.c > > +++ b/drivers/thermal/qcom/tsens.c > > @@ -599,6 +599,7 @@ 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; > > > > @@ -607,13 +608,21 @@ int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp) > > 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 (!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 (valid || ret) > > + break; > > + } while (!(ret = time_after_eq(jiffies, timeout))); > > + > > if (ret) > > return ret; > > With the overloading of 'ret' the return logic is getting a bit more > convoluted. Also the function should probably return -ETIMEDOUT or > some other meaningful error if the bit is never valid. > > How about keeping the 'while (!valid)' condition, and adding > > if (time_after_eq(jiffies, timeout)) > return -ETIMEDOUT; > > inside the loop? > I tried to refactor the code using some tag. Hope it's better that way and thanks for the review. Sending v2.
diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c index b1162e566a70..38afde1a599f 100644 --- a/drivers/thermal/qcom/tsens.c +++ b/drivers/thermal/qcom/tsens.c @@ -599,6 +599,7 @@ 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; @@ -607,13 +608,21 @@ int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp) 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 (!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 (valid || ret) + break; + } while (!(ret = time_after_eq(jiffies, timeout))); + if (ret) return ret; }
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. Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com> --- drivers/thermal/qcom/tsens.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-)