From mboxrd@z Thu Jan 1 00:00:00 1970 From: shawn.guo@linaro.org (Shawn Guo) Date: Thu, 13 Feb 2014 21:02:54 +0800 Subject: [PATCH] thermal: imx: update formula for thermal sensor In-Reply-To: <1392199595-1054-1-git-send-email-b20788@freescale.com> References: <1392199595-1054-1-git-send-email-b20788@freescale.com> Message-ID: <20140213130252.GB20842@S2101-09.ap.freescale.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Copy LAKML and pengutronix folks in case they have comments. On Wed, Feb 12, 2014 at 06:06:35PM +0800, Anson Huang wrote: > Thermal sensor used to need two calibration points which are > in fuse map to get a slope for converting thermal sensor's raw > data to real temperature in degree C. Due to the chip calibration > limitation, hardware team provides an universal formula to get > real temperature from internal thermal sensor raw data: > > Slope = 0.4297157 - (0.0015976 * 25C fuse); > > Update the formula, as there will be no hot point calibration > data in fuse map from now on. > > Signed-off-by: Anson Huang Acked-by: Shawn Guo Shawn > --- > drivers/thermal/imx_thermal.c | 39 ++++++++++++++++++++++++++------------- > 1 file changed, 26 insertions(+), 13 deletions(-) > > diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c > index 45af765..a99c631 100644 > --- a/drivers/thermal/imx_thermal.c > +++ b/drivers/thermal/imx_thermal.c > @@ -62,12 +62,16 @@ enum imx_thermal_trip { > #define IMX_POLLING_DELAY 2000 /* millisecond */ > #define IMX_PASSIVE_DELAY 1000 > > +#define FACTOR0 10000000 > +#define FACTOR1 15976 > +#define FACTOR2 4297157 > + > struct imx_thermal_data { > struct thermal_zone_device *tz; > struct thermal_cooling_device *cdev; > enum thermal_device_mode mode; > struct regmap *tempmon; > - int c1, c2; /* See formula in imx_get_sensor_data() */ > + u32 c1, c2; /* See formula in imx_get_sensor_data() */ > unsigned long temp_passive; > unsigned long temp_critical; > unsigned long alarm_temp; > @@ -84,7 +88,7 @@ static void imx_set_alarm_temp(struct imx_thermal_data *data, > int alarm_value; > > data->alarm_temp = alarm_temp; > - alarm_value = (alarm_temp - data->c2) / data->c1; > + alarm_value = (data->c2 - alarm_temp) / data->c1; > regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_ALARM_VALUE_MASK); > regmap_write(map, TEMPSENSE0 + REG_SET, alarm_value << > TEMPSENSE0_ALARM_VALUE_SHIFT); > @@ -136,7 +140,7 @@ static int imx_get_temp(struct thermal_zone_device *tz, unsigned long *temp) > n_meas = (val & TEMPSENSE0_TEMP_CNT_MASK) >> TEMPSENSE0_TEMP_CNT_SHIFT; > > /* See imx_get_sensor_data() for formula derivation */ > - *temp = data->c2 + data->c1 * n_meas; > + *temp = data->c2 - n_meas * data->c1; > > /* Update alarm value to next higher trip point */ > if (data->alarm_temp == data->temp_passive && *temp >= data->temp_passive) > @@ -305,6 +309,7 @@ static int imx_get_sensor_data(struct platform_device *pdev) > int t1, t2, n1, n2; > int ret; > u32 val; > + u64 temp64; > > map = syscon_regmap_lookup_by_phandle(pdev->dev.of_node, > "fsl,tempmon-data"); > @@ -330,6 +335,8 @@ static int imx_get_sensor_data(struct platform_device *pdev) > * [31:20] - sensor value @ 25C > * [19:8] - sensor value of hot > * [7:0] - hot temperature value > + * Use universal formula now and only need sensor value @ 25C > + * slope = 0.4297157 - (0.0015976 * 25C fuse) > */ > n1 = val >> 20; > n2 = (val & 0xfff00) >> 8; > @@ -337,20 +344,26 @@ static int imx_get_sensor_data(struct platform_device *pdev) > t1 = 25; /* t1 always 25C */ > > /* > - * Derived from linear interpolation, > - * Tmeas = T2 + (Nmeas - N2) * (T1 - T2) / (N1 - N2) > + * Derived from linear interpolation: > + * slope = 0.4297157 - (0.0015976 * 25C fuse) > + * slope = (FACTOR2 - FACTOR1 * n1) / FACTOR0 > + * (Nmeas - n1) / (Tmeas - t1) = slope > * We want to reduce this down to the minimum computation necessary > * for each temperature read. Also, we want Tmeas in millicelsius > * and we don't want to lose precision from integer division. So... > - * milli_Tmeas = 1000 * T2 + 1000 * (Nmeas - N2) * (T1 - T2) / (N1 - N2) > - * Let constant c1 = 1000 * (T1 - T2) / (N1 - N2) > - * milli_Tmeas = (1000 * T2) + c1 * (Nmeas - N2) > - * milli_Tmeas = (1000 * T2) + (c1 * Nmeas) - (c1 * N2) > - * Let constant c2 = (1000 * T2) - (c1 * N2) > - * milli_Tmeas = c2 + (c1 * Nmeas) > + * Tmeas = (Nmeas - n1) / slope + t1 > + * milli_Tmeas = 1000 * (Nmeas - n1) / slope + 1000 * t1 > + * milli_Tmeas = -1000 * (n1 - Nmeas) / slope + 1000 * t1 > + * Let constant c1 = (-1000 / slope) > + * milli_Tmeas = (n1 - Nmeas) * c1 + 1000 * t1 > + * Let constant c2 = n1 *c1 + 1000 * t1 > + * milli_Tmeas = c2 - Nmeas * c1 > */ > - data->c1 = 1000 * (t1 - t2) / (n1 - n2); > - data->c2 = 1000 * t2 - data->c1 * n2; > + temp64 = FACTOR0; > + temp64 *= 1000; > + do_div(temp64, FACTOR1 * n1 - FACTOR2); > + data->c1 = temp64; > + data->c2 = n1 * data->c1 + 1000 * t1; > > /* > * Set the default passive cooling trip point to 20 ?C below the > -- > 1.7.9.5 > >