diff options
| -rw-r--r-- | drivers/thermal/imx_thermal.c | 38 |
1 files changed, 21 insertions, 17 deletions
diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c index 3e794c7..3fb23c2 100644 --- a/drivers/thermal/imx_thermal.c +++ b/drivers/thermal/imx_thermal.c @@ -1,5 +1,5 @@ /* - * (C) Copyright 2014 Freescale Semiconductor, Inc. + * (C) Copyright 2014-2015 Freescale Semiconductor, Inc. * Author: Nitin Garg <nitin.garg@freescale.com> * Ye Li <Ye.Li@freescale.com> * @@ -23,8 +23,9 @@ #define TEMPERATURE_HOT 80 #define TEMPERATURE_MAX 125 #define FACTOR0 10000000 -#define FACTOR1 15976 -#define FACTOR2 4297157 +#define FACTOR1 16549 +#define FACTOR2 4445388 +#define OFFSET 3580661 #define MEASURE_FREQ 327 #define TEMPSENSE0_TEMP_CNT_SHIFT 8 @@ -44,39 +45,42 @@ static int read_cpu_temperature(struct udevice *dev) unsigned int *priv = dev_get_priv(dev); u32 fuse = *priv; int t1, n1; - u32 c1, c2; + u64 c1, c2; u64 temp64; /* * Sensor data layout: * [31:20] - sensor value @ 25C * We use universal formula now and only need sensor value @ 25C - * slope = 0.4297157 - (0.0015976 * 25C fuse) + * slope = 0.4445388 - (0.0016549 * 25C fuse) */ n1 = fuse >> 20; t1 = 25; /* t1 always 25C */ /* * Derived from linear interpolation: - * slope = 0.4297157 - (0.0015976 * 25C fuse) + * slope = 0.4445388 - (0.0016549 * 25C fuse) * slope = (FACTOR2 - FACTOR1 * n1) / FACTOR0 + * offset = 3.580661 + * offset = OFFSET / 1000000 * (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... - * 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 + * Tmeas = (Nmeas - n1) / slope + t1 + offset + * milli_Tmeas = 1000000 * (Nmeas - n1) / slope + 1000000 * t1 + OFFSET + * milli_Tmeas = -1000000 * (n1 - Nmeas) / slope + 1000000 * t1 + OFFSET + * Let constant c1 = (-1000000 / slope) + * milli_Tmeas = (n1 - Nmeas) * c1 + 1000000 * t1 + OFFSET + * Let constant c2 = n1 *c1 + 1000000 * t1 + * milli_Tmeas = (c2 - Nmeas * c1) / 1000000 + OFFSET + * Tmeas = ((c2 - Nmeas * c1) + OFFSET) / 1000000 */ temp64 = FACTOR0; - temp64 *= 1000; + temp64 *= 1000000; do_div(temp64, FACTOR1 * n1 - FACTOR2); c1 = temp64; - c2 = n1 * c1 + 1000 * t1; + c2 = n1 * c1 + 1000000 * t1; /* * now we only use single measure, every time we read @@ -108,8 +112,8 @@ static int read_cpu_temperature(struct udevice *dev) >> TEMPSENSE0_TEMP_CNT_SHIFT; writel(TEMPSENSE0_FINISHED, &anatop->tempsense0_clr); - /* milli_Tmeas = c2 - Nmeas * c1 */ - temperature = (c2 - n_meas * c1)/1000; + /* Tmeas = (c2 - Nmeas * c1 + OFFSET) / 1000000 */ + temperature = lldiv(c2 - n_meas * c1 + OFFSET, 1000000); /* power down anatop thermal sensor */ writel(TEMPSENSE0_POWER_DOWN, &anatop->tempsense0_set); |