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From:   Andrey Smirnov <andrew.smirnov@gmail.com>
To:     Daniel Lezcano <daniel.lezcano@linaro.org>
Cc:     Andrey Smirnov <andrew.smirnov@gmail.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        Chris Healy <cphealy@gmail.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Angus Ainslie <angus@akkea.ca>, linux-imx@nxp.com,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v8 10/12] thermal: qoriq: Do not report invalid temperature reading
Date:   Tue, 10 Dec 2019 08:41:51 -0800
Message-Id: <20191210164153.10463-11-andrew.smirnov@gmail.com>
In-Reply-To: <20191210164153.10463-1-andrew.smirnov@gmail.com>
References: <20191210164153.10463-1-andrew.smirnov@gmail.com>
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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@gmail.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Lucas Stach <l.stach@pengutronix.de>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Angus Ainslie (Purism) <angus@akkea.ca>
Cc: linux-imx@nxp.com
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/thermal/qoriq_thermal.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/qoriq_thermal.c b/drivers/thermal/qoriq_thermal.c
index 6c5e53ea7711..b684d3ceda69 100644
--- a/drivers/thermal/qoriq_thermal.c
+++ b/drivers/thermal/qoriq_thermal.c
@@ -48,6 +48,7 @@
 #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
 					   */
@@ -80,8 +81,24 @@ 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;
-- 
2.21.0