thermal/drivers/tsens: Fix bug in sensor enable for msm8960

Device based on tsens VER_0 contains a hardware bug that results in some
problem with sensor enablement. Sensor id 6-11 can't be enabled
selectively and all of them must be enabled in one step.
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Acked-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210420183343.2272-6-ansuelsmth@gmail.com

drivers/thermal/qcom/tsens-8960.c

@@ -27,9 +27,9 @@
 #define EN			BIT(0)
 #define SW_RST			BIT(1)
 #define SENSOR0_EN		BIT(3)
+#define MEASURE_PERIOD		BIT(18)
 #define SLP_CLK_ENA		BIT(26)
 #define SLP_CLK_ENA_8660	BIT(24)
-#define MEASURE_PERIOD		1
 #define SENSOR0_SHIFT		3
 
 /* INT_STATUS_ADDR bitmasks */
@@ -126,17 +126,34 @@ static int resume_8960(struct tsens_priv *priv)
 static int enable_8960(struct tsens_priv *priv, int id)
 {
 	int ret;
-	u32 reg, mask;
+	u32 reg, mask = BIT(id);
 
 	ret = regmap_read(priv->tm_map, CNTL_ADDR, &reg);
 	if (ret)
 		return ret;
 
-	mask = BIT(id + SENSOR0_SHIFT);
+	/* HARDWARE BUG:
+	 * On platforms with more than 6 sensors, all remaining sensors
+	 * must be enabled together, otherwise undefined results are expected.
+	 * (Sensor 6-7 disabled, Sensor 3 disabled...) In the original driver,
+	 * all the sensors are enabled in one step hence this bug is not
+	 * triggered.
+	 */
+	if (id > 5)
+		mask = GENMASK(10, 6);
+
+	mask <<= SENSOR0_SHIFT;
+
+	/* Sensors already enabled. Skip. */
+	if ((reg & mask) == mask)
+		return 0;
+
 	ret = regmap_write(priv->tm_map, CNTL_ADDR, reg | SW_RST);
 	if (ret)
 		return ret;
 
+	reg |= MEASURE_PERIOD;
+
 	if (priv->num_sensors > 1)
 		reg |= mask | SLP_CLK_ENA | EN;
 	else