iio: adc: meson-saradc: enable the temperature sensor two more SoCs

Meson8b and Meson8m2 use the same logic to convert the ADC register
value to celsius, which is different from Meson8:
- Meson8 has different multiplier and divider values
- Meson8 uses a 4-bit TSC (temperature sensor coefficient) which fits
  into the 4-bit field in the MESON_SAR_ADC_DELTA_10 register:
  MESON_SAR_ADC_DELTA_10_TS_C_MASK. Meson8b and Meson8m2 have a 5-bit
  TSC which requires writing the upper-most bit into the
  MESON_HHI_DPLL_TOP_0[9] register from the HHI register area.

This adds support for the temperature sensor on the Meson8b and Meson8m2
SoCs by implementing the logic to write the upper-most TSC bit into the
HHI register area. The SoC-specific values (temperature_trimming_bits,
temperature_multiplier, temperature_divider) are added - these simply
integrate into the existing infrastructure (which was implemented for
Meson8) and thus require no further changes to the existing temperature
calculation logic.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/meson_saradc.c

@@ -26,6 +26,7 @@
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
+#include <linux/mfd/syscon.h>
 
 #define MESON_SAR_ADC_REG0					0x00
 	#define MESON_SAR_ADC_REG0_PANEL_DETECT			BIT(31)
@@ -174,6 +175,9 @@
 #define MESON_SAR_ADC_EFUSE_BYTE3_UPPER_ADC_VAL			GENMASK(6, 0)
 #define MESON_SAR_ADC_EFUSE_BYTE3_IS_CALIBRATED			BIT(7)
 
+#define MESON_HHI_DPLL_TOP_0					0x318
+#define MESON_HHI_DPLL_TOP_0_TSC_BIT4				BIT(9)
+
 /* for use with IIO_VAL_INT_PLUS_MICRO */
 #define MILLION							1000000
 
@@ -280,6 +284,7 @@ struct meson_sar_adc_priv {
 	struct completion			done;
 	int					calibbias;
 	int					calibscale;
+	struct regmap				*tsc_regmap;
 	bool					temperature_sensor_calibrated;
 	u8					temperature_sensor_coefficient;
 	u16					temperature_sensor_adc_val;
@@ -727,6 +732,15 @@ static int meson_sar_adc_temp_sensor_init(struct iio_dev *indio_dev)
 		return ret;
 	}
 
+	priv->tsc_regmap =
+		syscon_regmap_lookup_by_phandle(indio_dev->dev.parent->of_node,
+						"amlogic,hhi-sysctrl");
+	if (IS_ERR(priv->tsc_regmap)) {
+		dev_err(indio_dev->dev.parent,
+			"failed to get amlogic,hhi-sysctrl regmap\n");
+		return PTR_ERR(priv->tsc_regmap);
+	}
+
 	read_len = MESON_SAR_ADC_EFUSE_BYTES;
 	buf = nvmem_cell_read(temperature_calib, &read_len);
 	if (IS_ERR(buf)) {
@@ -861,6 +875,22 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
 				    priv->temperature_sensor_coefficient);
 		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
 				   MESON_SAR_ADC_DELTA_10_TS_C_MASK, regval);
+
+		if (priv->param->temperature_trimming_bits == 5) {
+			if (priv->temperature_sensor_coefficient & BIT(4))
+				regval = MESON_HHI_DPLL_TOP_0_TSC_BIT4;
+			else
+				regval = 0;
+
+			/*
+			 * bit [4] (the 5th bit when starting to count at 1)
+			 * of the TSC is located in the HHI register area.
+			 */
+			regmap_update_bits(priv->tsc_regmap,
+					   MESON_HHI_DPLL_TOP_0,
+					   MESON_HHI_DPLL_TOP_0_TSC_BIT4,
+					   regval);
+		}
 	} else {
 		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
 				   MESON_SAR_ADC_DELTA_10_TS_REVE1, 0);
@@ -1064,6 +1094,9 @@ static const struct meson_sar_adc_param meson_sar_adc_meson8b_param = {
 	.bandgap_reg = MESON_SAR_ADC_DELTA_10,
 	.regmap_config = &meson_sar_adc_regmap_config_meson8,
 	.resolution = 10,
+	.temperature_trimming_bits = 5,
+	.temperature_multiplier = 10,
+	.temperature_divider = 32,
 };
 
 static const struct meson_sar_adc_param meson_sar_adc_gxbb_param = {