[PATCH 12/16] hwmon: (mr75203) modify the temperature equation

[Eliav Farber]

Modify the equation and coefficients to convert the digital output to
temperature according to series 5 of the Moortec Embedded Temperature
Sensor (METS) datasheet:
T = G + H * (n / cal5 - 0.5) + J * F

The G, H and J coefficients are multiplied by 1000 to get the
temperature in milli-Celsius.

Signed-off-by: Eliav Farber <farbere@xxxxxxxxxx>
---
 drivers/hwmon/mr75203.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c
index 8d8883301ff5..59e2dc8fa333 100644
--- a/drivers/hwmon/mr75203.c
+++ b/drivers/hwmon/mr75203.c
@@ -100,9 +100,10 @@
 
 #define PVT_POLL_DELAY_US	20
 #define PVT_POLL_TIMEOUT_US	20000
-#define PVT_H_CONST		100000
-#define PVT_CAL5_CONST		2047
-#define PVT_G_CONST		40000
+#define PVT_H_CONST		60000
+#define PVT_G_CONST		200000
+#define PVT_J_CONST		-100
+#define PVT_CAL5_CONST		4094
 #define PVT_CONV_BITS		10
 #define PVT_N_CONST		90
 #define PVT_R_CONST		245805
@@ -156,7 +157,6 @@ static int pvt_read_temp(struct device *dev, u32 attr, int channel, long *val)
 	struct regmap *t_map = pvt->t_map;
 	u32 stat, nbs;
 	int ret;
-	u64 tmp;
 
 	switch (attr) {
 	case hwmon_temp_input:
@@ -174,12 +174,13 @@ static int pvt_read_temp(struct device *dev, u32 attr, int channel, long *val)
 		nbs &= SAMPLE_DATA_MSK;
 
 		/*
-		 * Convert the register value to
-		 * degrees centigrade temperature
+		 * Convert the register value to degrees centigrade temperature:
+		 * T = G + H * (n / cal5 - 0.5) + J * F
 		 */
-		tmp = nbs * PVT_H_CONST;
-		do_div(tmp, PVT_CAL5_CONST);
-		*val = tmp - PVT_G_CONST - pvt->ip_freq;
+		*val = PVT_G_CONST;
+		*val += PVT_H_CONST * nbs / PVT_CAL5_CONST;
+		*val -= PVT_H_CONST / 2;
+		*val += PVT_J_CONST * pvt->ip_freq / HZ_PER_MHZ;
 
 		return 0;
 	default:
@@ -311,7 +312,7 @@ static int pvt_init(struct pvt_device *pvt)
 		    (key >> 1) << CLK_SYNTH_HI_SFT |
 		    (key >> 1) << CLK_SYNTH_HOLD_SFT | CLK_SYNTH_EN;
 
-	pvt->ip_freq = sys_freq * 100 / (key + 2);
+	pvt->ip_freq = clk_get_rate(pvt->clk) / (key + 2);
 
 	if (t_num) {
 		ret = regmap_write(t_map, SDIF_SMPL_CTRL, 0x0);
-- 
2.37.1