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@xxxxxxxxx>
> ---
> 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 :)
