arm: mx6: update temperature calculation code
authorLothar Waßmann <LW@KARO-electronics.de>
Fri, 9 Jan 2015 10:49:53 +0000 (11:49 +0100)
committerLothar Waßmann <LW@KARO-electronics.de>
Fri, 9 Jan 2015 10:49:53 +0000 (11:49 +0100)
There are i.MX6 processors where the calibration values for the hot
points are not programmed. Use the temperature calculation code from
Linux kernel to accomodate this.

arch/arm/cpu/armv7/mx6/soc.c

index 8d9b141..6ca4a1e 100644 (file)
@@ -8,6 +8,7 @@
  */
 
 #include <common.h>
+#include <div64.h>
 #include <asm/errno.h>
 #include <asm/io.h>
 #include <asm/arch/imx-regs.h>
@@ -41,7 +42,6 @@ DECLARE_GLOBAL_DATA_PTR;
 #endif
 #define TEMP_AVG_COUNT                 5
 #define TEMP_WARN_THRESHOLD            5
-#define REG_VALUE_TO_CEL(ratio, raw) ((raw_n40c - raw) * 100 / ratio - 40)
 
 #define __data __attribute__((section(".data")))
 
@@ -171,10 +171,56 @@ static void set_vddsoc(u32 mv)
 
 static u32 __data thermal_calib;
 
+#define FACTOR0                                10000000
+#define FACTOR1                                15976
+#define FACTOR2                                4297157
+
+int raw_to_celsius(unsigned int raw, unsigned int raw_25c, unsigned int raw_hot,
+               unsigned int hot_temp)
+{
+       int temperature;
+
+       if (raw_hot != 0 && hot_temp != 0) {
+               unsigned int raw_n40c, ratio;
+
+               ratio = ((raw_25c - raw_hot) * 100) / (hot_temp - 25);
+               raw_n40c = raw_25c + (13 * ratio) / 20;
+               if (raw <= raw_n40c)
+                       temperature = (raw_n40c - raw) * 100 / ratio - 40;
+               else
+                       temperature = TEMPERATURE_MIN;
+       } else {
+               u64 temp64 = FACTOR0;
+               unsigned int c1, c2;
+               /*
+                * 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...
+                * 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
+                */
+               temp64 *= 1000;
+               do_div(temp64, FACTOR1 * raw_25c - FACTOR2);
+               c1 = temp64;
+               c2 = raw_25c * c1 + 1000 * 25;
+               temperature = (c2 - raw * c1) / 1000;
+       }
+       return temperature;
+}
+
 int read_cpu_temperature(void)
 {
        unsigned int reg, tmp, i;
-       unsigned int raw_25c, raw_hot, hot_temp, raw_n40c, ratio;
+       unsigned int raw_25c, raw_hot, hot_temp;
        int temperature;
        struct anatop_regs *const anatop = (void *)ANATOP_BASE_ADDR;
        struct mx6_ocotp_regs *const ocotp_regs = (void *)OCOTP_BASE_ADDR;
@@ -198,9 +244,6 @@ int read_cpu_temperature(void)
        raw_hot = (thermal_calib & 0xfff00) >> 8;
        hot_temp = thermal_calib & 0xff;
 
-       ratio = ((raw_25c - raw_hot) * 100) / (hot_temp - 25);
-       raw_n40c = raw_25c + (13 * ratio) / 20;
-
        /* now we only using single measure, every time we measure
         * the temperature, we will power on/off the anadig module
         */
@@ -208,33 +251,43 @@ int read_cpu_temperature(void)
        writel(BM_ANADIG_ANA_MISC0_REFTOP_SELBIASOFF, &anatop->ana_misc0_set);
 
        /* write measure freq */
-       reg = readl(&anatop->tempsense1);
-       reg &= ~BM_ANADIG_TEMPSENSE1_MEASURE_FREQ;
-       reg |= 327;
-       writel(reg, &anatop->tempsense1);
-
+       writel(327, &anatop->tempsense1);
        writel(BM_ANADIG_TEMPSENSE0_MEASURE_TEMP, &anatop->tempsense0_clr);
        writel(BM_ANADIG_TEMPSENSE0_FINISHED, &anatop->tempsense0_clr);
        writel(BM_ANADIG_TEMPSENSE0_MEASURE_TEMP, &anatop->tempsense0_set);
 
-       tmp = 0;
-       /* read five times of temperature values to get average*/
-       for (i = 0; i < 5; i++) {
+       /* average the temperature value over multiple readings */
+       for (i = 0; i < TEMP_AVG_COUNT; i++) {
+               static int failed;
+               int limit = 100;
+
                while ((readl(&anatop->tempsense0) &
-                               BM_ANADIG_TEMPSENSE0_FINISHED) == 0)
+                               BM_ANADIG_TEMPSENSE0_FINISHED) == 0) {
                        udelay(10000);
-               reg = readl(&anatop->tempsense0);
-               tmp += (reg & BM_ANADIG_TEMPSENSE0_TEMP_VALUE) >>
+                       if (--limit < 0)
+                               break;
+               }
+               if ((readl(&anatop->tempsense0) &
+                               BM_ANADIG_TEMPSENSE0_FINISHED) == 0) {
+                       if (!failed) {
+                               printf("Failed to read temp sensor\n");
+                               failed = 1;
+                       }
+                       return 0;
+               }
+               failed = 0;
+               reg = (readl(&anatop->tempsense0) &
+                       BM_ANADIG_TEMPSENSE0_TEMP_VALUE) >>
                        BP_ANADIG_TEMPSENSE0_TEMP_VALUE;
+               if (i == 0)
+                       tmp = reg;
+               else
+                       tmp = (tmp * i + reg) / (i + 1);
                writel(BM_ANADIG_TEMPSENSE0_FINISHED,
                        &anatop->tempsense0_clr);
        }
 
-       tmp = tmp / 5;
-       if (tmp <= raw_n40c)
-               temperature = REG_VALUE_TO_CEL(ratio, tmp);
-       else
-               temperature = TEMPERATURE_MIN;
+       temperature = raw_to_celsius(tmp, raw_25c, raw_hot, hot_temp);
 
        /* power down anatop thermal sensor */
        writel(BM_ANADIG_TEMPSENSE0_POWER_DOWN, &anatop->tempsense0_set);