iio: adc: break out common code from SPMI VADC

The SPMI VADC and the earlier XOADC share a subset of
common code, so to be able to use the same code in both
drivers, we break out a separate file with the common code,
prefix exported functions that are no longer static with
qcom_* and bake an object qcom-spmi-vadc.o that contains both
files: qcom-vadc-common.o and qcom-spmi-vadc-core.o.

As we need to follow the procedure for making a kernel module
or compiled in object from several files, but still want to
produce the same module name, rename the qcom-spmi-vadc.c
file to qcom-spmi-vadc-core.c so we can bake the two objects
into qcom-spmi-vadc.o

Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arm-msm@vger.kernel.org
Cc: Ivan T. Ivanov <iivanov.xz@gmail.com>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Rama Krishna Phani A <rphani@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/Kconfig

@@ -496,6 +496,9 @@ config PALMAS_GPADC
 	  is used in smartphones and tablets and supports a 16 channel
 	  general purpose ADC.
 
+config QCOM_VADC_COMMON
+	tristate
+
 config QCOM_SPMI_IADC
 	tristate "Qualcomm SPMI PMIC current ADC"
 	depends on SPMI
@@ -514,6 +517,7 @@ config QCOM_SPMI_VADC
 	tristate "Qualcomm SPMI PMIC voltage ADC"
 	depends on SPMI
 	select REGMAP_SPMI
+	select QCOM_VADC_COMMON
 	help
 	  This is the IIO Voltage ADC driver for Qualcomm QPNP VADC Chip.
 

drivers/iio/adc/Makefile

@@ -48,6 +48,7 @@ obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
 obj-$(CONFIG_NAU7802) += nau7802.o
 obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
 obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
+obj-$(CONFIG_QCOM_VADC_COMMON) += qcom-vadc-common.o
 obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
 obj-$(CONFIG_RCAR_GYRO_ADC) += rcar-gyroadc.o
 obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o

drivers/iio/adc/qcom-vadc-common.c

+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/bitops.h>
+#include <linux/math64.h>
+#include <linux/log2.h>
+#include <linux/err.h>
+
+#include "qcom-vadc-common.h"
+
+/* Voltage to temperature */
+static const struct vadc_map_pt adcmap_100k_104ef_104fb[] = {
+	{1758,	-40},
+	{1742,	-35},
+	{1719,	-30},
+	{1691,	-25},
+	{1654,	-20},
+	{1608,	-15},
+	{1551,	-10},
+	{1483,	-5},
+	{1404,	0},
+	{1315,	5},
+	{1218,	10},
+	{1114,	15},
+	{1007,	20},
+	{900,	25},
+	{795,	30},
+	{696,	35},
+	{605,	40},
+	{522,	45},
+	{448,	50},
+	{383,	55},
+	{327,	60},
+	{278,	65},
+	{237,	70},
+	{202,	75},
+	{172,	80},
+	{146,	85},
+	{125,	90},
+	{107,	95},
+	{92,	100},
+	{79,	105},
+	{68,	110},
+	{59,	115},
+	{51,	120},
+	{44,	125}
+};
+
+static int qcom_vadc_map_voltage_temp(const struct vadc_map_pt *pts,
+				      u32 tablesize, s32 input, s64 *output)
+{
+	bool descending = 1;
+	u32 i = 0;
+
+	if (!pts)
+		return -EINVAL;
+
+	/* Check if table is descending or ascending */
+	if (tablesize > 1) {
+		if (pts[0].x < pts[1].x)
+			descending = 0;
+	}
+
+	while (i < tablesize) {
+		if ((descending) && (pts[i].x < input)) {
+			/* table entry is less than measured*/
+			 /* value and table is descending, stop */
+			break;
+		} else if ((!descending) &&
+				(pts[i].x > input)) {
+			/* table entry is greater than measured*/
+			/*value and table is ascending, stop */
+			break;
+		}
+		i++;
+	}
+
+	if (i == 0) {
+		*output = pts[0].y;
+	} else if (i == tablesize) {
+		*output = pts[tablesize - 1].y;
+	} else {
+		/* result is between search_index and search_index-1 */
+		/* interpolate linearly */
+		*output = (((s32)((pts[i].y - pts[i - 1].y) *
+			(input - pts[i - 1].x)) /
+			(pts[i].x - pts[i - 1].x)) +
+			pts[i - 1].y);
+	}
+
+	return 0;
+}
+
+static void qcom_vadc_scale_calib(const struct vadc_linear_graph *calib_graph,
+				  u16 adc_code,
+				  bool absolute,
+				  s64 *scale_voltage)
+{
+	*scale_voltage = (adc_code - calib_graph->gnd);
+	*scale_voltage *= calib_graph->dx;
+	*scale_voltage = div64_s64(*scale_voltage, calib_graph->dy);
+	if (absolute)
+		*scale_voltage += calib_graph->dx;
+
+	if (*scale_voltage < 0)
+		*scale_voltage = 0;
+}
+
+static int qcom_vadc_scale_volt(const struct vadc_linear_graph *calib_graph,
+				const struct vadc_prescale_ratio *prescale,
+				bool absolute, u16 adc_code,
+				int *result_uv)
+{
+	s64 voltage = 0, result = 0;
+
+	qcom_vadc_scale_calib(calib_graph, adc_code, absolute, &voltage);
+
+	voltage = voltage * prescale->den;
+	result = div64_s64(voltage, prescale->num);
+	*result_uv = result;
+
+	return 0;
+}
+
+static int qcom_vadc_scale_therm(const struct vadc_linear_graph *calib_graph,
+				 const struct vadc_prescale_ratio *prescale,
+				 bool absolute, u16 adc_code,
+				 int *result_mdec)
+{
+	s64 voltage = 0, result = 0;
+	int ret;
+
+	qcom_vadc_scale_calib(calib_graph, adc_code, absolute, &voltage);
+
+	if (absolute)
+		voltage = div64_s64(voltage, 1000);
+
+	ret = qcom_vadc_map_voltage_temp(adcmap_100k_104ef_104fb,
+					 ARRAY_SIZE(adcmap_100k_104ef_104fb),
+					 voltage, &result);
+	if (ret)
+		return ret;
+
+	result *= 1000;
+	*result_mdec = result;
+
+	return 0;
+}
+
+static int qcom_vadc_scale_die_temp(const struct vadc_linear_graph *calib_graph,
+				    const struct vadc_prescale_ratio *prescale,
+				    bool absolute,
+				    u16 adc_code, int *result_mdec)
+{
+	s64 voltage = 0;
+	u64 temp; /* Temporary variable for do_div */
+
+	qcom_vadc_scale_calib(calib_graph, adc_code, absolute, &voltage);
+
+	if (voltage > 0) {
+		temp = voltage * prescale->den;
+		do_div(temp, prescale->num * 2);
+		voltage = temp;
+	} else {
+		voltage = 0;
+	}
+
+	voltage -= KELVINMIL_CELSIUSMIL;
+	*result_mdec = voltage;
+
+	return 0;
+}
+
+static int qcom_vadc_scale_chg_temp(const struct vadc_linear_graph *calib_graph,
+				    const struct vadc_prescale_ratio *prescale,
+				    bool absolute,
+				    u16 adc_code, int *result_mdec)
+{
+	s64 voltage = 0, result = 0;
+
+	qcom_vadc_scale_calib(calib_graph, adc_code, absolute, &voltage);
+
+	voltage = voltage * prescale->den;
+	voltage = div64_s64(voltage, prescale->num);
+	voltage = ((PMI_CHG_SCALE_1) * (voltage * 2));
+	voltage = (voltage + PMI_CHG_SCALE_2);
+	result =  div64_s64(voltage, 1000000);
+	*result_mdec = result;
+
+	return 0;
+}
+
+int qcom_vadc_scale(enum vadc_scale_fn_type scaletype,
+		    const struct vadc_linear_graph *calib_graph,
+		    const struct vadc_prescale_ratio *prescale,
+		    bool absolute,
+		    u16 adc_code, int *result)
+{
+	switch (scaletype) {
+	case SCALE_DEFAULT:
+		return qcom_vadc_scale_volt(calib_graph, prescale,
+					    absolute, adc_code,
+					    result);
+	case SCALE_THERM_100K_PULLUP:
+	case SCALE_XOTHERM:
+		return qcom_vadc_scale_therm(calib_graph, prescale,
+					     absolute, adc_code,
+					     result);
+	case SCALE_PMIC_THERM:
+		return qcom_vadc_scale_die_temp(calib_graph, prescale,
+						absolute, adc_code,
+						result);
+	case SCALE_PMI_CHG_TEMP:
+		return qcom_vadc_scale_chg_temp(calib_graph, prescale,
+						absolute, adc_code,
+						result);
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL(qcom_vadc_scale);
+
+int qcom_vadc_decimation_from_dt(u32 value)
+{
+	if (!is_power_of_2(value) || value < VADC_DECIMATION_MIN ||
+	    value > VADC_DECIMATION_MAX)
+		return -EINVAL;
+
+	return __ffs64(value / VADC_DECIMATION_MIN);
+}
+EXPORT_SYMBOL(qcom_vadc_decimation_from_dt);

drivers/iio/adc/qcom-vadc-common.h

+/*
+ * Code shared between the different Qualcomm PMIC voltage ADCs
+ */
+
+#ifndef QCOM_VADC_COMMON_H
+#define QCOM_VADC_COMMON_H
+
+#define VADC_CONV_TIME_MIN_US			2000
+#define VADC_CONV_TIME_MAX_US			2100
+
+/* Min ADC code represents 0V */
+#define VADC_MIN_ADC_CODE			0x6000
+/* Max ADC code represents full-scale range of 1.8V */
+#define VADC_MAX_ADC_CODE			0xa800
+
+#define VADC_ABSOLUTE_RANGE_UV			625000
+#define VADC_RATIOMETRIC_RANGE			1800
+
+#define VADC_DEF_PRESCALING			0 /* 1:1 */
+#define VADC_DEF_DECIMATION			0 /* 512 */
+#define VADC_DEF_HW_SETTLE_TIME			0 /* 0 us */
+#define VADC_DEF_AVG_SAMPLES			0 /* 1 sample */
+#define VADC_DEF_CALIB_TYPE			VADC_CALIB_ABSOLUTE
+
+#define VADC_DECIMATION_MIN			512
+#define VADC_DECIMATION_MAX			4096
+
+#define VADC_HW_SETTLE_DELAY_MAX		10000
+#define VADC_AVG_SAMPLES_MAX			512
+
+#define KELVINMIL_CELSIUSMIL			273150
+
+#define PMI_CHG_SCALE_1				-138890
+#define PMI_CHG_SCALE_2				391750000000LL
+
+/**
+ * struct vadc_map_pt - Map the graph representation for ADC channel
+ * @x: Represent the ADC digitized code.
+ * @y: Represent the physical data which can be temperature, voltage,
+ *     resistance.
+ */
+struct vadc_map_pt {
+	s32 x;
+	s32 y;
+};
+
+/*
+ * VADC_CALIB_ABSOLUTE: uses the 625mV and 1.25V as reference channels.
+ * VADC_CALIB_RATIOMETRIC: uses the reference voltage (1.8V) and GND for
+ * calibration.
+ */
+enum vadc_calibration {
+	VADC_CALIB_ABSOLUTE = 0,
+	VADC_CALIB_RATIOMETRIC
+};
+
+/**
+ * struct vadc_linear_graph - Represent ADC characteristics.
+ * @dy: numerator slope to calculate the gain.
+ * @dx: denominator slope to calculate the gain.
+ * @gnd: A/D word of the ground reference used for the channel.
+ *
+ * Each ADC device has different offset and gain parameters which are
+ * computed to calibrate the device.
+ */
+struct vadc_linear_graph {
+	s32 dy;
+	s32 dx;
+	s32 gnd;
+};
+
+/**
+ * struct vadc_prescale_ratio - Represent scaling ratio for ADC input.
+ * @num: the inverse numerator of the gain applied to the input channel.
+ * @den: the inverse denominator of the gain applied to the input channel.
+ */
+struct vadc_prescale_ratio {
+	u32 num;
+	u32 den;
+};
+
+/**
+ * enum vadc_scale_fn_type - Scaling function to convert ADC code to
+ *				physical scaled units for the channel.
+ * SCALE_DEFAULT: Default scaling to convert raw adc code to voltage (uV).
+ * SCALE_THERM_100K_PULLUP: Returns temperature in millidegC.
+ *				 Uses a mapping table with 100K pullup.
+ * SCALE_PMIC_THERM: Returns result in milli degree's Centigrade.
+ * SCALE_XOTHERM: Returns XO thermistor voltage in millidegC.
+ * SCALE_PMI_CHG_TEMP: Conversion for PMI CHG temp
+ */
+enum vadc_scale_fn_type {
+	SCALE_DEFAULT = 0,
+	SCALE_THERM_100K_PULLUP,
+	SCALE_PMIC_THERM,
+	SCALE_XOTHERM,
+	SCALE_PMI_CHG_TEMP,
+};
+
+int qcom_vadc_scale(enum vadc_scale_fn_type scaletype,
+		    const struct vadc_linear_graph *calib_graph,
+		    const struct vadc_prescale_ratio *prescale,
+		    bool absolute,
+		    u16 adc_code, int *result_mdec);
+
+int qcom_vadc_decimation_from_dt(u32 value);
+
+#endif /* QCOM_VADC_COMMON_H */