thermal: qoriq: Do not report invalid temperature reading

Before returning measured temperature data to upper layer we need to
make sure that the reading was marked as "valid" to avoid reporting
bogus data.

Signed-off-by: Andrey Smirnov <[email protected]>
Reviewed-by: Daniel Lezcano <[email protected]>
Tested-by: Lucas Stach <[email protected]>
Cc: Chris Healy <[email protected]>
Cc: Lucas Stach <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Daniel Lezcano <[email protected]>
Cc: Angus Ainslie (Purism) <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Daniel Lezcano <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

1 files changed, 18 insertions, 1 deletions

diff --git a/drivers/thermal/qoriq_thermal.c b/drivers/thermal/qoriq_thermal.c
index 9a455948ddf0..1730dbe5eeb6 100644
--- a/drivers/thermal/qoriq_thermal.c
+++ b/drivers/thermal/qoriq_thermal.c
@@ -49,6 +49,7 @@
 #define REGS_TRITSR(n)	(0x100 + 16 * (n)) /* Immediate Temperature
 					    * Site Register
 					    */
+#define TRITSR_V	BIT(31)
 #define REGS_TTRnCR(n)	(0xf10 + 4 * (n)) /* Temperature Range n
 					   * Control Register
 					   */
@@ -81,8 +82,24 @@ static int tmu_get_temp(void *p, int *temp)
 	struct qoriq_sensor *qsensor = p;
 	struct qoriq_tmu_data *qdata = qoriq_sensor_to_data(qsensor);
 	u32 val;
+	/*
+	 * REGS_TRITSR(id) has the following layout:
+	 *
+	 * 31  ... 7 6 5 4 3 2 1 0
+	 *  V          TEMP
+	 *
+	 * Where V bit signifies if the measurement is ready and is
+	 * within sensor range. TEMP is an 8 bit value representing
+	 * temperature in C.
+	 */
+	if (regmap_read_poll_timeout(qdata->regmap,
+				     REGS_TRITSR(qsensor->id),
+				     val,
+				     val & TRITSR_V,
+				     USEC_PER_MSEC,
+				     10 * USEC_PER_MSEC))
+		return -ENODATA;
 
-	regmap_read(qdata->regmap, REGS_TRITSR(qsensor->id), &val);
 	*temp = (val & 0xff) * 1000;
 
 	return 0;