thermal: stm32: Improve temperature computing

Change the way of computing to avoid rounds by 1 or 2 degrees.
Also simplify the sampling time management that is hard-coded
to maximum value during probe.

Signed-off-by: Pascal Paillet <p.paillet@st.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200110101605.24984-6-p.paillet@st.com

diff --git a/drivers/thermal/st/stm_thermal.c b/drivers/thermal/st/stm_thermal.c
index 29e7ee8..aaf25ca 100644 (file)
--- a/drivers/thermal/st/stm_thermal.c
+++ b/drivers/thermal/st/stm_thermal.c
@@ -59,7 +59,6 @@
 
 /* Less significant bit position definitions */
 #define TS1_T0_POS             16
-#define TS1_SMP_TIME_POS       16
 #define TS1_HITTHD_POS         16
 #define TS1_LITTHD_POS         0
 #define HSREF_CLK_DIV_POS      24
@@ -83,15 +82,10 @@
 #define ONE_MHZ                        1000000
 #define POLL_TIMEOUT           5000
 #define STARTUP_TIME           40
-#define TS1_T0_VAL0            30
-#define TS1_T0_VAL1            130
+#define TS1_T0_VAL0            30000  /* 30 celsius */
+#define TS1_T0_VAL1            130000 /* 130 celsius */
 #define NO_HW_TRIG             0
-
-/* The Thermal Framework expects millidegrees */
-#define mcelsius(temp)         ((temp) * 1000)
-
-/* The Sensor expects oC degrees */
-#define celsius(temp)          ((temp) / 1000)
+#define SAMPLING_TIME          15
 
 struct stm_thermal_sensor {
        struct device *dev;
@@ -280,27 +274,17 @@ static int stm_thermal_calculate_threshold(struct stm_thermal_sensor *sensor,
                                           int temp, u32 *th)
 {
        int freqM;
-       u32 sampling_time;
-
-       /* Retrieve the number of periods to sample */
-       sampling_time = (readl_relaxed(sensor->base + DTS_CFGR1_OFFSET) &
-                       TS1_SMP_TIME_MASK) >> TS1_SMP_TIME_POS;
 
        /* Figure out the CLK_PTAT frequency for a given temperature */
-       freqM = ((temp - sensor->t0) * sensor->ramp_coeff)
-                + sensor->fmt0;
-
-       dev_dbg(sensor->dev, "%s: freqM for threshold = %d Hz",
-               __func__, freqM);
+       freqM = ((temp - sensor->t0) * sensor->ramp_coeff) / 1000 +
+               sensor->fmt0;
 
        /* Figure out the threshold sample number */
-       *th = clk_get_rate(sensor->clk);
+       *th = clk_get_rate(sensor->clk) * SAMPLING_TIME / freqM;
        if (!*th)
                return -EINVAL;
 
-       *th = *th / freqM;
-
-       *th *= sampling_time;
+       dev_dbg(sensor->dev, "freqM=%d Hz, threshold=0x%x", freqM, *th);
 
        return 0;
 }
@@ -368,40 +352,26 @@ static int stm_thermal_set_trips(void *data, int low, int high)
 static int stm_thermal_get_temp(void *data, int *temp)
 {
        struct stm_thermal_sensor *sensor = data;
-       u32 sampling_time;
+       u32 periods;
        int freqM, ret;
 
        if (sensor->mode != THERMAL_DEVICE_ENABLED)
                return -EAGAIN;
 
-       /* Retrieve the number of samples */
-       ret = readl_poll_timeout(sensor->base + DTS_DR_OFFSET, freqM,
-                                (freqM & TS1_MFREQ_MASK), STARTUP_TIME,
-                                POLL_TIMEOUT);
-
+       /* Retrieve the number of periods sampled */
+       ret = readl_relaxed_poll_timeout(sensor->base + DTS_DR_OFFSET, periods,
+                                        (periods & TS1_MFREQ_MASK),
+                                        STARTUP_TIME, POLL_TIMEOUT);
        if (ret)
                return ret;
 
-       if (!freqM)
-               return -ENODATA;
-
-       /* Retrieve the number of periods sampled */
-       sampling_time = (readl_relaxed(sensor->base + DTS_CFGR1_OFFSET) &
-                       TS1_SMP_TIME_MASK) >> TS1_SMP_TIME_POS;
-
-       /* Figure out the number of samples per period */
-       freqM /= sampling_time;
-
        /* Figure out the CLK_PTAT frequency */
-       freqM = clk_get_rate(sensor->clk) / freqM;
+       freqM = (clk_get_rate(sensor->clk) * SAMPLING_TIME) / periods;
        if (!freqM)
                return -EINVAL;
 
-       dev_dbg(sensor->dev, "%s: freqM=%d\n", __func__, freqM);
-
        /* Figure out the temperature in mili celsius */
-       *temp = mcelsius(sensor->t0 + ((freqM - sensor->fmt0) /
-                        sensor->ramp_coeff));
+       *temp = (freqM - sensor->fmt0) * 1000 / sensor->ramp_coeff + sensor->t0;
 
        return 0;
 }