[PATCH v14 5/9] drivers: thermal: tsens: Fix bug in sensor enable for msm8960

[Ansuel Smith]

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 <ansuels...@gmail.com>
Acked-by: Thara Gopinath <thara.gopin...@linaro.org>
---
 drivers/thermal/qcom/tsens-8960.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/qcom/tsens-8960.c 
b/drivers/thermal/qcom/tsens-8960.c
index 86585f439985..95fcccafae14 100644
--- a/drivers/thermal/qcom/tsens-8960.c
+++ b/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
-- 
2.30.2