thermal/drivers/tsens: Add timeout to get_temp_tsens_valid

[ Upstream commit d012f9189fda0f3a1b303780ba0bbc7298d0d349 ]

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 and convert
to poll_timeout generic macro.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211007172859.583-1-ansuelsmth@gmail.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c
index b1162e5..99a8d9f 100644 (file)
--- a/drivers/thermal/qcom/tsens.c
+++ b/drivers/thermal/qcom/tsens.c
@@ -603,22 +603,21 @@ int get_temp_tsens_valid(const struct tsens_sensor *s, int *temp)
        int ret;
 
        /* VER_0 doesn't have VALID bit */
-       if (tsens_version(priv) >= VER_0_1) {
-               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 (tsens_version(priv) == VER_0)
+               goto get_temp;
+
+       /* 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.
+        * Wait 1 us since it's the min of poll_timeout macro.
+        * Old value was 400 ns.
+        */
+       ret = regmap_field_read_poll_timeout(priv->rf[valid_idx], valid,
+                                            valid, 1, 20 * USEC_PER_MSEC);
+       if (ret)
+               return ret;
 
+get_temp:
        /* Valid bit is set, OK to read the temperature */
        *temp = tsens_hw_to_mC(s, temp_idx);