linux-kernel - [PATCH v5 10/12] thermal: qoriq: Do not report invalid temperature reading

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Date:   Tue, 23 Apr 2019 23:48:28 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     linux-pm@...r.kernel.org
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Lucas Stach <l.stach@...gutronix.de>,
        Chris Healy <cphealy@...il.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Angus Ainslie <angus@...ea.ca>, linux-imx@....com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v5 10/12] 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 <andrew.smirnov@...il.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@...aro.org>
Tested-by: Lucas Stach <l.stach@...gutronix.de>
Cc: Chris Healy <cphealy@...il.com>
Cc: Lucas Stach <l.stach@...gutronix.de>
Cc: Eduardo Valentin <edubezval@...il.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Angus Ainslie (Purism) <angus@...ea.ca>
Cc: linux-imx@....com
Cc: linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/thermal/qoriq_thermal.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/qoriq_thermal.c b/drivers/thermal/qoriq_thermal.c
index d8d9f567a632..f97d0cc82b2b 100644
--- a/drivers/thermal/qoriq_thermal.c
+++ b/drivers/thermal/qoriq_thermal.c
@@ -37,6 +37,7 @@
 #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
 					   */
@@ -48,10 +49,25 @@ static int tmu_get_temp(int id, void *p, int *temp)
 {
 	struct qoriq_tmu_data *qdata = p;
 	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(id),
+				     val,
+				     val & TRITSR_V,
+				     USEC_PER_MSEC,
+				     10 * USEC_PER_MSEC))
+		return -ENODATA;
 
-	regmap_read(qdata->regmap, REGS_TRITSR(id), &val);
 	*temp = (val & 0xff) * 1000;
-
 	return 0;
 }
 
-- 
2.20.1