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@xxxxxxxxx>
> > ---
> > 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.
