Modify the equation and coefficients used 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
Where:
*) G = 60, H = 200, cal5 = 4094, J = -0.1.
*) F = frequency clock in MHz.
*) n is the digital output.
In code, the G, H and J coefficients are multiplied by a factor of 1000
to get the temperature in milli-Celsius.
Final result is clamped in case it exceeds min/max thresholds.
Change is done since it is unclear where the current equation and
coefficients came from.
Signed-off-by: Eliav Farber <farbere@xxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
V4 -> V3:
- Change 'not clear' to 'unclear' in commit message.
- Add _mC prefix to temperature mix/max defines.
- Add SERIES5 to coefficient defines.
V3 -> V2:
- Protect from overflow.
- Add temperature clamping.
- Add better documentation.
drivers/hwmon/mr75203.c | 33 +++++++++++++++++++++++++--------
1 file changed, 25 insertions(+), 8 deletions(-)
diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c
index 8a6ae72fed20..0de64642cc42 100644
--- a/drivers/hwmon/mr75203.c
+++ b/drivers/hwmon/mr75203.c
@@ -102,13 +102,19 @@
#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_CONV_BITS 10
#define PVT_N_CONST 90
#define PVT_R_CONST 245805
+#define PVT_TEMP_MIN_mC -40000
+#define PVT_TEMP_MAX_mC 125000
+
+/* Temperature coefficients for series 5 */
+#define PVT_SERIES5_H_CONST 200000
+#define PVT_SERIES5_G_CONST 60000
+#define PVT_SERIES5_J_CONST -100
+#define PVT_SERIES5_CAL5_CONST 4094
+
#define PRE_SCALER_X1 1
#define PRE_SCALER_X2 2
@@ -174,13 +180,26 @@ static umode_t pvt_is_visible(const void *data, enum hwmon_sensor_types type,
return 0;
}
+static long pvt_calc_temp(struct pvt_device *pvt, u32 nbs)
+{
+ /*
+ * Convert the register value to degrees centigrade temperature:
+ * T = G + H * (n / cal5 - 0.5) + J * F
+ */
+ s64 tmp = PVT_SERIES5_G_CONST +
+ PVT_SERIES5_H_CONST * (s64)nbs / PVT_SERIES5_CAL5_CONST -
+ PVT_SERIES5_H_CONST / 2 +
+ PVT_SERIES5_J_CONST * (s64)pvt->ip_freq / HZ_PER_MHZ;
+
+ return clamp_val(tmp, PVT_TEMP_MIN_mC, PVT_TEMP_MAX_mC);
+}
+
static int pvt_read_temp(struct device *dev, u32 attr, int channel, long *val)
{
struct pvt_device *pvt = dev_get_drvdata(dev);
struct regmap *t_map = pvt->t_map;
u32 stat, nbs;
int ret;
- u64 tmp;
switch (attr) {
case hwmon_temp_input:
@@ -201,9 +220,7 @@ static int pvt_read_temp(struct device *dev, u32 attr, int channel, long *val)
* Convert the register value to
* degrees centigrade temperature
*/
- tmp = nbs * PVT_H_CONST;
- do_div(tmp, PVT_CAL5_CONST);
- *val = tmp - PVT_G_CONST - pvt->ip_freq;
+ *val = pvt_calc_temp(pvt, nbs);
return 0;
default:
@@ -337,7 +354,7 @@ 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
