thermistor: move thermistor tables into common code

The exact same 2 lookup tables are in multiple board files. We seem to
reuse the 2 thermistor circuit enough that we should single source them
in a common location.

BRANCH=none
BUG=none
TEST=yorp sensors still function properly

Change-Id: Ic393c609c78c8a51c55a67b639c1fb9e6c387d8a
Signed-off-by: Jett Rink <jettrink@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1100943
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Justin TerAvest <teravest@chromium.org>

4 files changed, 188 insertions, 54 deletions

diff --git a/driver/build.mk b/driver/build.mk
index 68a412423d..230ca34af3 100644
--- a/driver/build.mk
+++ b/driver/build.mk
@@ -94,6 +94,7 @@ driver-$(CONFIG_TOUCHPAD_ELAN)+=touchpad_elan.o
 driver-$(CONFIG_TOUCHPAD_ST)+=touchpad_st.o
 
 # Thermistors
+driver-$(CONFIG_THERMISTOR)+=temp_sensor/thermistor.o
 driver-$(CONFIG_THERMISTOR_NCP15WB)+=temp_sensor/thermistor_ncp15wb.o
 
 # Type-C port controller (TCPC) drivers
diff --git a/driver/temp_sensor/thermistor.c b/driver/temp_sensor/thermistor.c
new file mode 100644
index 0000000000..d9c70f7386
--- /dev/null
+++ b/driver/temp_sensor/thermistor.c
@@ -0,0 +1,147 @@
+/* Copyright 2018 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Common thermistor code for Chrome EC */
+
+#include "adc.h"
+#include "common.h"
+#include "thermistor.h"
+#include "util.h"
+
+int thermistor_linear_interpolate(uint16_t mv,
+		const struct thermistor_info *info)
+{
+	const struct thermistor_data_pair *data = info->data;
+	int v_high = 0, v_low = 0, t_low, t_high, num_steps;
+	int head, tail, mid = 0;
+
+	/* We need at least two points to form a line. */
+	ASSERT(info->num_pairs >= 2);
+
+	/*
+	 * If input value is out of bounds return the lowest or highest
+	 * value in the data sets provided.
+	 */
+	if (mv > data[0].mv * info->scaling_factor)
+		return data[0].temp;
+	else if (mv < data[info->num_pairs - 1].mv * info->scaling_factor)
+		return data[info->num_pairs - 1].temp;
+
+	head = 0;
+	tail = info->num_pairs - 1;
+	while (head != tail) {
+		mid = (head + tail) / 2;
+		v_high = data[mid].mv * info->scaling_factor;
+		v_low = data[mid + 1].mv * info->scaling_factor;
+
+		if ((mv <= v_high) && (mv >= v_low))
+			break;
+		else if (mv > v_high)
+			tail = mid;
+		else if (mv < v_low)
+			head = mid + 1;
+	}
+
+	t_low = data[mid].temp;
+	t_high = data[mid + 1].temp;
+
+	/*
+	 * The obvious way of doing this is to figure out how many mV per
+	 * degree are in between the two points (mv_per_deg_c), and then how
+	 * many of those exist between the input voltage and voltage of
+	 * lower temperature :
+	 *   1. mv_per_deg_c = (v_high - v_low) / (t_high - t_low)
+	 *   2. num_steps = (v_high - mv) / mv_per_deg_c
+	 *   3. result = t_low + num_steps
+	 *
+	 * Combine #1 and #2 to mitigate precision loss due to integer division.
+	 */
+	num_steps = ((v_high - mv) * (t_high - t_low)) / (v_high - v_low);
+	return t_low + num_steps;
+}
+
+#ifdef CONFIG_STEINHART_HART_3V3_51K1_47K_4050B
+/*
+ * Data derived from Steinhart-Hart equation in a resistor divider circuit with
+ * Vdd=3300mV, R = 51.1Kohm, and thermistor (B = 4050, T0 = 298.15 K, nominal
+ * resistance (R0) = 47Kohm).
+ */
+#define THERMISTOR_SCALING_FACTOR_51_47 11
+static const struct thermistor_data_pair thermistor_data_51_47[] = {
+	{ 2512 / THERMISTOR_SCALING_FACTOR_51_47, 0   },
+	{ 2158 / THERMISTOR_SCALING_FACTOR_51_47, 10  },
+	{ 1772 / THERMISTOR_SCALING_FACTOR_51_47, 20  },
+	{ 1398 / THERMISTOR_SCALING_FACTOR_51_47, 30  },
+	{ 1070 / THERMISTOR_SCALING_FACTOR_51_47, 40  },
+	{  803 / THERMISTOR_SCALING_FACTOR_51_47, 50  },
+	{  597 / THERMISTOR_SCALING_FACTOR_51_47, 60  },
+	{  443 / THERMISTOR_SCALING_FACTOR_51_47, 70  },
+	{  329 / THERMISTOR_SCALING_FACTOR_51_47, 80  },
+	{  285 / THERMISTOR_SCALING_FACTOR_51_47, 85  },
+	{  247 / THERMISTOR_SCALING_FACTOR_51_47, 90  },
+	{  214 / THERMISTOR_SCALING_FACTOR_51_47, 95  },
+	{  187 / THERMISTOR_SCALING_FACTOR_51_47, 100 },
+};
+
+static const struct thermistor_info thermistor_info_51_47 = {
+	.scaling_factor = THERMISTOR_SCALING_FACTOR_51_47,
+	.num_pairs = ARRAY_SIZE(thermistor_data_51_47),
+	.data = thermistor_data_51_47,
+};
+
+int get_temp_3v3_51k1_47k_4050b(int idx_adc, int *temp_ptr)
+{
+	int mv = adc_read_channel(idx_adc);
+
+	if (mv < 0)
+		return EC_ERROR_UNKNOWN;
+
+	*temp_ptr = thermistor_linear_interpolate(mv, &thermistor_info_51_47);
+	*temp_ptr = C_TO_K(*temp_ptr);
+	return EC_SUCCESS;
+}
+#endif /* CONFIG_STEINHART_HART_3V3_51K1_47K_4050B */
+
+#ifdef CONFIG_STEINHART_HART_3V3_13K7_47K_4050B
+/*
+ * Data derived from Steinhart-Hart equation in a resistor divider circuit with
+ * Vdd=3300mV, R = 13.7Kohm, and thermistor (B = 4050, T0 = 298.15 K, nominal
+ * resistance (R0) = 47Kohm).
+ */
+#define THERMISTOR_SCALING_FACTOR_13_47 13
+static const struct thermistor_data_pair thermistor_data_13_47[] = {
+	{ 3044 / THERMISTOR_SCALING_FACTOR_13_47, 0   },
+	{ 2890 / THERMISTOR_SCALING_FACTOR_13_47, 10  },
+	{ 2680 / THERMISTOR_SCALING_FACTOR_13_47, 20  },
+	{ 2418 / THERMISTOR_SCALING_FACTOR_13_47, 30  },
+	{ 2117 / THERMISTOR_SCALING_FACTOR_13_47, 40  },
+	{ 1800 / THERMISTOR_SCALING_FACTOR_13_47, 50  },
+	{ 1490 / THERMISTOR_SCALING_FACTOR_13_47, 60  },
+	{ 1208 / THERMISTOR_SCALING_FACTOR_13_47, 70  },
+	{  966 / THERMISTOR_SCALING_FACTOR_13_47, 80  },
+	{  860 / THERMISTOR_SCALING_FACTOR_13_47, 85  },
+	{  766 / THERMISTOR_SCALING_FACTOR_13_47, 90  },
+	{  679 / THERMISTOR_SCALING_FACTOR_13_47, 95  },
+	{  603 / THERMISTOR_SCALING_FACTOR_13_47, 100 },
+};
+
+static const struct thermistor_info thermistor_info_13_47 = {
+	.scaling_factor = THERMISTOR_SCALING_FACTOR_13_47,
+	.num_pairs = ARRAY_SIZE(thermistor_data_13_47),
+	.data = thermistor_data_13_47,
+};
+
+int get_temp_3v3_13k7_47k_4050b(int idx_adc, int *temp_ptr)
+{
+	int mv = adc_read_channel(idx_adc);
+
+	if (mv < 0)
+		return EC_ERROR_UNKNOWN;
+
+	*temp_ptr = thermistor_linear_interpolate(mv, &thermistor_info_13_47);
+	*temp_ptr = C_TO_K(*temp_ptr);
+	return EC_SUCCESS;
+}
+#endif /* CONFIG_STEINHART_HART_3V3_13K7_47K_4050B */
diff --git a/driver/temp_sensor/thermistor.h b/driver/temp_sensor/thermistor.h
index af3ea398c8..49edee5451 100644
--- a/driver/temp_sensor/thermistor.h
+++ b/driver/temp_sensor/thermistor.h
@@ -33,7 +33,7 @@ struct thermistor_info {
 };
 
 /**
- * @brief Calculate temperature using linear interpolation of data points.
+ * Calculate temperature using linear interpolation of data points.
  *
  * Given a set of datapoints, the algorithm will calculate the "step" in
  * between each one in order to interpolate missing entries.
@@ -44,8 +44,9 @@ struct thermistor_info {
  * @return	temperature in C
  */
 int thermistor_linear_interpolate(uint16_t mv,
-				const struct thermistor_info *info);
+				  const struct thermistor_info *info);
 
+#ifdef CONFIG_THERMISTOR_NCP15WB
 /**
  * ncp15wb temperature conversion routine.
  *
@@ -54,5 +55,42 @@ int thermistor_linear_interpolate(uint16_t mv,
  * @return	temperature in C.
  */
 int ncp15wb_calculate_temp(uint16_t adc);
+#endif /* CONFIG_THERMISTOR_NCP15WB */
+
+#ifdef CONFIG_STEINHART_HART_3V3_13K7_47K_4050B
+/**
+ * Reads the specified ADC channel and uses a lookup table and interpolation to
+ * return a temperature in degrees K.
+ *
+ * The lookup table is based off of a resistor divider circuit on 3.3V with a
+ * 13.7K resistor in series with a thermistor with nominal value of 47K (at 25C)
+ * and a B (25/100) value of 4050.
+ *
+ * @param idx_adc	The idx value from the temp_sensor_t struct, which is
+ *			the ADC channel to read and convert to degrees K
+ * @param temp_ptr	Destination for temperature (in degrees K)
+ *
+ * @return EC_SUCCESS, or non-zero if error.
+ */
+int get_temp_3v3_13k7_47k_4050b(int idx_adc, int *temp_ptr);
+#endif
+
+#ifdef CONFIG_STEINHART_HART_3V3_51K1_47K_4050B
+/**
+ * Reads the specified ADC channel and uses a lookup table and interpolation to
+ * return a temperature in degrees K.
+ *
+ * The lookup table is based off of a resistor divider circuit on 3.3V with a
+ * 51.1K resistor in series with a thermistor with nominal value of 47K (at 25C)
+ * and a B (25/100) value of 4050.
+ *
+ * @param idx_adc	The idx value from the temp_sensor_t struct, which is
+ *			the ADC channel to read and convert to degrees K
+ * @param temp_ptr	Destination for temperature (in degrees K)
+ *
+ * @return EC_SUCCESS, or non-zero if error.
+ */
+int get_temp_3v3_51k1_47k_4050b(int idx_adc, int *temp_ptr);
+#endif
 
 #endif  /* __CROS_EC_TEMP_SENSOR_THERMISTOR_NCP15WB_H */
diff --git a/driver/temp_sensor/thermistor_ncp15wb.c b/driver/temp_sensor/thermistor_ncp15wb.c
index dae8251575..51e884ed35 100644
--- a/driver/temp_sensor/thermistor_ncp15wb.c
+++ b/driver/temp_sensor/thermistor_ncp15wb.c
@@ -98,55 +98,3 @@ int ncp15wb_calculate_temp(uint16_t adc)
 
 	return temp;
 }
-
-int thermistor_linear_interpolate(uint16_t mv,
-		const struct thermistor_info *info)
-{
-	const struct thermistor_data_pair *data = info->data;
-	int v_high = 0, v_low = 0, t_low, t_high, num_steps;
-	int head, tail, mid = 0;
-
-	/* We need at least two points to form a line. */
-	ASSERT(info->num_pairs >= 2);
-
-	/*
-	 * If input value is out of bounds return the lowest or highest
-	 * value in the data sets provided.
-	 */
-	if (mv > data[0].mv * info->scaling_factor)
-		return data[0].temp;
-	else if (mv < data[info->num_pairs - 1].mv * info->scaling_factor)
-		return data[info->num_pairs - 1].temp;
-
-	head = 0;
-	tail = info->num_pairs - 1;
-	while (head != tail) {
-		mid = (head + tail) / 2;
-		v_high = data[mid].mv * info->scaling_factor;
-		v_low = data[mid + 1].mv * info->scaling_factor;
-
-		if ((mv <= v_high) && (mv >= v_low))
-			break;
-		else if (mv > v_high)
-			tail = mid;
-		else if (mv < v_low)
-			head = mid + 1;
-	}
-
-	t_low = data[mid].temp;
-	t_high = data[mid + 1].temp;
-
-	/*
-	 * The obvious way of doing this is to figure out how many mV per
-	 * degree are in between the two points (mv_per_deg_c), and then how
-	 * many of those exist between the input voltage and voltage of
-	 * lower temperature :
-	 *   1. mv_per_deg_c = (v_high - v_low) / (t_high - t_low)
-	 *   2. num_steps = (v_high - mv) / mv_per_deg_c
-	 *   3. result = t_low + num_steps
-	 *
-	 * Combine #1 and #2 to mitigate precision loss due to integer division.
-	 */
-	num_steps = ((v_high - mv) * (t_high - t_low)) / (v_high - v_low);
-	return t_low + num_steps;
-}