From mboxrd@z Thu Jan 1 00:00:00 1970 From: rui.zhang@intel.com (Zhang Rui) Date: Thu, 27 Feb 2014 14:54:22 +0800 Subject: [PATCH] thermal: imx: update formula for thermal sensor In-Reply-To: <20140213130252.GB20842@S2101-09.ap.freescale.net> References: <1392199595-1054-1-git-send-email-b20788@freescale.com> <20140213130252.GB20842@S2101-09.ap.freescale.net> Message-ID: <1393484062.2637.15.camel@rzhang1-mobl4> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, 2014-02-13 at 21:02 +0800, Shawn Guo wrote: > 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 > applied. thanks, rui > > --- > > 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 > > > > >