meson-saradc: add chip temperature support

Channel 6 of the SAR ADC can be switched between two inputs:
SAR_ADC_CH6 input (an actual pad on the SoC) and the signal from the temperature sensor inside the SoC.

To get usable results from the temperature sensor we need to read the corresponding calibration data from the eFuse and pass it to the SAR ADC (bits [3:0]) and (on Meson8b and Meson8m2) to a scratch register in the HHI region.
If the temperature sensor is not calibrated (the eFuse data contains a bit for this) then the driver will return -ENOTSUPP when trying to read the temperature.

This only enables the temperature sensor for the Meson8, Meson8b and Meson8m2 SoCs because on the newer, 64-bit SoCs (GXBB, GXL and GXM) the temperature sensor inside SAR ADC is firmware-controlled (by BL30, we can simply use the SCPI hwmon driver to get the chip temperature).

To keep the devicetree interface backwards compatible we simply skip the temperature sensor initialization if no eFuse nvmem cell is passed via devicetree.

The public documentation for the SAR ADC IP block does not explain how to use the registers to read the temperature. The logic from this patch is based on reading and understanding Amlogic's GPL kernel sources.

Signed-off-by Martin Blumenstingl <[email protected]>

---
 drivers/iio/adc/meson_saradc.c | 274 +++++++++++++++++++++++++++++----
 1 file changed, 248 insertions(+), 26 deletions(-)

drivers/iio/adc/meson_saradc.c +2 -0

index 028ccd218f82..df1e45805c23 100644
@@ -18,6 +18,7 @@
 #include <linux/io.h>
 #include <linux/iio/iio.h>
 #include <linux/module.h>
+#include <linux/nvmem-consumer.h>
 #include <linux/interrupt.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>

@@ -25,6 +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)

drivers/iio/adc/meson_saradc.c +3 -2

+
 /* for use with IIO_VAL_INT_PLUS_MICRO */
 #define MILLION							1000000
 

@@ -175,16 +188,27 @@
 	.address = _chan,						\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
 				BIT(IIO_CHAN_INFO_AVERAGE_RAW),		\
-	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\
-				BIT(IIO_CHAN_INFO_CALIBBIAS) |		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_CALIBBIAS) |	\
 				BIT(IIO_CHAN_INFO_CALIBSCALE),		\

drivers/iio/adc/meson_saradc.c +34 -0

+	.channel = _chan,						\
+	.address = MESON_SAR_ADC_VOLTAGE_AND_TEMP_CHANNEL,		\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
+				BIT(IIO_CHAN_INFO_AVERAGE_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |		\
+					BIT(IIO_CHAN_INFO_SCALE) |	\
+					BIT(IIO_CHAN_INFO_ENABLE),	\
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_CALIBBIAS) |	\
+				BIT(IIO_CHAN_INFO_CALIBSCALE),		\
+	.datasheet_name = "TEMP_SENSOR",				\
+}
+
 static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
 	MESON_SAR_ADC_CHAN(0),
 	MESON_SAR_ADC_CHAN(1),

@@ -197,6 +221,19 @@ static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
 	IIO_CHAN_SOFT_TIMESTAMP(8),
 };
 
+static const struct iio_chan_spec meson_sar_adc_and_temp_iio_channels[] = {
+	MESON_SAR_ADC_CHAN(0),
+	MESON_SAR_ADC_CHAN(1),
+	MESON_SAR_ADC_CHAN(2),
+	MESON_SAR_ADC_CHAN(3),
+	MESON_SAR_ADC_CHAN(4),
+	MESON_SAR_ADC_CHAN(5),
+	MESON_SAR_ADC_CHAN(6),
+	MESON_SAR_ADC_CHAN(7),
+	MESON_SAR_ADC_TEMP_CHAN(8),
+	IIO_CHAN_SOFT_TIMESTAMP(9),
+};
+
 enum meson_sar_adc_avg_mode {
 	NO_AVERAGING = 0x0,
 	MEAN_AVERAGING = 0x1,

@@ -225,6 +262,11 @@ struct meson_sar_adc_param {
 	u32					bandgap_reg;
 	unsigned int				resolution;
 	const struct regmap_config		*regmap_config;
+	u8					temperature_trimming_bits;
+	unsigned int				temperature_multiplier;
+	unsigned int				temperature_divider;
+	const struct iio_chan_spec		*channels;
+	unsigned int				num_channels;
 };
 
 struct meson_sar_adc_data {

@@ -246,6 +288,10 @@ 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;
 };
 
 static const struct regmap_config meson_sar_adc_regmap_config_gxbb = {

drivers/iio/adc/meson_saradc.c +195 -17

+		if (chan->type == IIO_TEMP)
+			regmap_update_bits(priv->regmap,
+					   MESON_SAR_ADC_DELTA_10,
+					   MESON_SAR_ADC_DELTA_10_TEMP_SEL,
+					   MESON_SAR_ADC_DELTA_10_TEMP_SEL);
+		else
+			regmap_update_bits(priv->regmap,
+					   MESON_SAR_ADC_DELTA_10,
+					   MESON_SAR_ADC_DELTA_10_TEMP_SEL, 0);
+	}
 }
 
 static void meson_sar_adc_set_chan7_mux(struct iio_dev *indio_dev,

@@ -506,8 +560,12 @@ static int meson_sar_adc_get_sample(struct iio_dev *indio_dev,
 				    enum meson_sar_adc_num_samples avg_samples,
 				    int *val)
 {
+	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 	int ret;
 
+	if (chan->type == IIO_TEMP && !priv->temperature_sensor_calibrated)
+		return -ENOTSUPP;
+
 	ret = meson_sar_adc_lock(indio_dev);
 	if (ret)
 		return ret;

@@ -555,17 +613,31 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
 		break;
 
 	case IIO_CHAN_INFO_SCALE:
-		ret = regulator_get_voltage(priv->vref);
-		if (ret < 0) {
-			dev_err(indio_dev->dev.parent,
-				"failed to get vref voltage: %d\n", ret);
-			return ret;
+		if (chan->type == IIO_VOLTAGE) {
+			ret = regulator_get_voltage(priv->vref);
+			if (ret < 0) {
+				dev_err(indio_dev->dev.parent,
+					"failed to get vref voltage: %d\n",
+					ret);
+				return ret;
+			}
+
+			*val = ret / 1000;
+			*val2 = priv->param->resolution;
+			return IIO_VAL_FRACTIONAL_LOG2;
+		} else if (chan->type == IIO_TEMP) {
+			/* SoC specific multiplier and divider */
+			*val = priv->param->temperature_multiplier;
+			*val2 = priv->param->temperature_divider;
+
+			/* celsius to millicelsius */
+			*val *= 1000;
+
+			return IIO_VAL_FRACTIONAL;
+		} else {
+			return -EINVAL;
 		}
 
-		*val = ret / 1000;
-		*val2 = priv->param->resolution;
-		return IIO_VAL_FRACTIONAL_LOG2;
-
 	case IIO_CHAN_INFO_CALIBBIAS:
 		*val = priv->calibbias;
 		return IIO_VAL_INT;

@@ -575,6 +647,17 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
 		*val2 = priv->calibscale % MILLION;
 		return IIO_VAL_INT_PLUS_MICRO;
 
+	case IIO_CHAN_INFO_OFFSET:
+		*val = DIV_ROUND_CLOSEST(MESON_SAR_ADC_TEMP_OFFSET *
+					 priv->param->temperature_divider,
+					 priv->param->temperature_multiplier);
+		*val -= priv->temperature_sensor_adc_val;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_ENABLE:
+		*val = priv->temperature_sensor_calibrated;
+		return IIO_VAL_INT;
+
 	default:
 		return -EINVAL;
 	}

@@ -625,6 +708,77 @@ static int meson_sar_adc_clk_init(struct iio_dev *indio_dev,
 	return 0;
 }
 
+static int meson_sar_adc_temp_sensor_init(struct iio_dev *indio_dev)
+{
+	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
+	u8 *buf, trimming_bits, trimming_mask, upper_adc_val;
+	struct nvmem_cell *temperature_calib;
+	size_t read_len;
+	int ret;
+
+	temperature_calib = devm_nvmem_cell_get(&indio_dev->dev,
+						"temperature_calib");
+	if (IS_ERR(temperature_calib)) {
+		ret = PTR_ERR(temperature_calib);
+
+		/*
+		 * leave the temperature sensor disabled if no calibration data
+		 * was passed via nvmem-cells.
+		 */
+		if (ret == -ENODEV)
+			return 0;
+
+		if (ret != -EPROBE_DEFER)
+			dev_err(indio_dev->dev.parent,
+				"failed to get temperature_calib cell\n");
+
+		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)) {
+		dev_err(indio_dev->dev.parent,
+			"failed to read temperature_calib cell\n");
+		return PTR_ERR(buf);
+	} else if (read_len != MESON_SAR_ADC_EFUSE_BYTES) {
+		kfree(buf);
+		dev_err(indio_dev->dev.parent,
+			"invalid read size of temperature_calib cell\n");
+		return -EINVAL;
+	}
+
+	trimming_bits = priv->param->temperature_trimming_bits;
+	trimming_mask = BIT(trimming_bits) - 1;
+
+	if (buf[3] & MESON_SARADC_EFUSE_BYTE3_IS_CALIBRATED)
+		priv->temperature_sensor_calibrated = true;
+	else
+		priv->temperature_sensor_calibrated = false;
+
+	priv->temperature_sensor_coefficient = buf[2] & trimming_mask;
+
+	upper_adc_val = FIELD_GET(MESON_SARADC_EFUSE_BYTE3_UPPER_ADC_VAL,
+				  buf[3]);
+
+	priv->temperature_sensor_adc_val = buf[2];
+	priv->temperature_sensor_adc_val |= upper_adc_val << BITS_PER_BYTE;
+	priv->temperature_sensor_adc_val >>= trimming_bits;
+
+	kfree(buf);
+
+	return 0;
+}
+
 static int meson_sar_adc_init(struct iio_dev *indio_dev)
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);

@@ -649,10 +803,12 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
 
 	meson_sar_adc_stop_sample_engine(indio_dev);
 
-	/* update the channel 6 MUX to select the temperature sensor */
+	/*
+	 * disable this bit as seems to be only relevant for Meson6 (based
+	 * on the vendor driver), which we don't support at the moment.
+	 */
 	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
-			MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL,
-			MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL);
+			MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL, 0);
 
 	/* disable all channels by default */
 	regmap_write(priv->regmap, MESON_SAR_ADC_CHAN_LIST, 0x0);

@@ -709,6 +865,45 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
 	regval |= MESON_SAR_ADC_AUX_SW_XP_DRIVE_SW;
 	regmap_write(priv->regmap, MESON_SAR_ADC_AUX_SW, regval);
 
+	if (priv->temperature_sensor_calibrated) {
+		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
+				   MESON_SAR_ADC_DELTA_10_TS_REVE1,
+				   MESON_SAR_ADC_DELTA_10_TS_REVE1);
+		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
+				   MESON_SAR_ADC_DELTA_10_TS_REVE0,
+				   MESON_SAR_ADC_DELTA_10_TS_REVE0);
+
+		/*
+		 * set bits [3:0] of the TSC (temperature sensor coefficient)
+		 * to get the correct values when reading the temperature.
+		 */
+		regval = FIELD_PREP(MESON_SAR_ADC_DELTA_10_TS_C_MASK,
+				    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;
+
+			/*
+			 * the 5th bit (4th when starting to count at 0) of the
+			 * TSC is located in another 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);
+		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
+				   MESON_SAR_ADC_DELTA_10_TS_REVE0, 0);
+	}
+
 	ret = clk_set_parent(priv->adc_sel_clk, priv->clkin);
 	if (ret) {
 		dev_err(indio_dev->dev.parent,

@@ -894,6 +1089,24 @@ static const struct meson_sar_adc_param meson_sar_adc_meson8_param = {
 	.bandgap_reg = MESON_SAR_ADC_DELTA_10,
 	.regmap_config = &meson_sar_adc_regmap_config_meson8,
 	.resolution = 10,
+	.temperature_trimming_bits = 4,
+	.temperature_multiplier = 18 * 10000,
+	.temperature_divider = 1024 * 10 * 85,
+	.channels = meson_sar_adc_and_temp_iio_channels,
+	.num_channels = ARRAY_SIZE(meson_sar_adc_and_temp_iio_channels),
+};
+
+static const struct meson_sar_adc_param meson_sar_adc_meson8b_param = {
+	.has_bl30_integration = false,
+	.clock_rate = 1150000,
+	.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,
+	.channels = meson_sar_adc_and_temp_iio_channels,
+	.num_channels = ARRAY_SIZE(meson_sar_adc_and_temp_iio_channels),
 };
 
 static const struct meson_sar_adc_param meson_sar_adc_gxbb_param = {

@@ -902,6 +1115,8 @@ static const struct meson_sar_adc_param meson_sar_adc_gxbb_param = {
 	.bandgap_reg = MESON_SAR_ADC_REG11,
 	.regmap_config = &meson_sar_adc_regmap_config_gxbb,
 	.resolution = 10,
+	.channels = meson_sar_adc_iio_channels,
+	.num_channels = ARRAY_SIZE(meson_sar_adc_iio_channels),
 };
 
 static const struct meson_sar_adc_param meson_sar_adc_gxl_param = {

@@ -910,6 +1125,8 @@ static const struct meson_sar_adc_param meson_sar_adc_gxl_param = {
 	.bandgap_reg = MESON_SAR_ADC_REG11,
 	.regmap_config = &meson_sar_adc_regmap_config_gxbb,
 	.resolution = 12,
+	.channels = meson_sar_adc_iio_channels,
+	.num_channels = ARRAY_SIZE(meson_sar_adc_iio_channels),
 };
 
 static const struct meson_sar_adc_data meson_sar_adc_meson8_data = {

@@ -918,12 +1135,12 @@ static const struct meson_sar_adc_data meson_sar_adc_meson8_data = {
 };
 
 static const struct meson_sar_adc_data meson_sar_adc_meson8b_data = {
-	.param = &meson_sar_adc_meson8_param,
+	.param = &meson_sar_adc_meson8b_param,
 	.name = "meson-meson8b-saradc",
 };
 
 static const struct meson_sar_adc_data meson_sar_adc_meson8m2_data = {
-	.param = &meson_sar_adc_meson8_param,
+	.param = &meson_sar_adc_meson8b_param,
 	.name = "meson-meson8m2-saradc",
 };
 

@@ -1008,9 +1225,8 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 	indio_dev->dev.of_node = pdev->dev.of_node;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &meson_sar_adc_iio_info;
-
-	indio_dev->channels = meson_sar_adc_iio_channels;
-	indio_dev->num_channels = ARRAY_SIZE(meson_sar_adc_iio_channels);
+	indio_dev->channels = priv->param->channels;
+	indio_dev->num_channels = priv->param->num_channels;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	base = devm_ioremap_resource(&pdev->dev, res);

@@ -1078,6 +1294,12 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 
 	priv->calibscale = MILLION;
 
+	if (priv->param->temperature_trimming_bits) {
+		ret = meson_sar_adc_temp_sensor_init(indio_dev);
+		if (ret)
+			return ret;
+	}
+
 	ret = meson_sar_adc_init(indio_dev);
 	if (ret)
 		goto err;

On Sun, 28 Oct 2018, Martin Blumenstingl wrote:

comments below

Quoted 52 lines

Channel 6 of the SAR ADC can be switched between two inputs:
SAR_ADC_CH6 input (an actual pad on the SoC) and the signal from the temperature sensor inside the SoC.

To get usable results from the temperature sensor we need to read the corresponding calibration data from the eFuse and pass it to the SAR ADC (bits [3:0]) and (on Meson8b and Meson8m2) to a scratch register in the HHI region.
If the temperature sensor is not calibrated (the eFuse data contains a bit for this) then the driver will return -ENOTSUPP when trying to read the temperature.

This only enables the temperature sensor for the Meson8, Meson8b and Meson8m2 SoCs because on the newer, 64-bit SoCs (GXBB, GXL and GXM) the temperature sensor inside SAR ADC is firmware-controlled (by BL30, we can simply use the SCPI hwmon driver to get the chip temperature).

To keep the devicetree interface backwards compatible we simply skip the temperature sensor initialization if no eFuse nvmem cell is passed via devicetree.

The public documentation for the SAR ADC IP block does not explain how to use the registers to read the temperature. The logic from this patch is based on reading and understanding Amlogic's GPL kernel sources.

Signed-off-by Martin Blumenstingl <[email protected]>

---
 drivers/iio/adc/meson_saradc.c | 274 +++++++++++++++++++++++++++++----
 1 file changed, 248 insertions(+), 26 deletions(-)

drivers/iio/adc/meson_saradc.c +2 -0

index 028ccd218f82..df1e45805c23 100644
@@ -18,6 +18,7 @@
 #include <linux/io.h>
 #include <linux/iio/iio.h>
 #include <linux/module.h>
+#include <linux/nvmem-consumer.h>
 #include <linux/interrupt.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>

@@ -25,6 +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)

@@ -165,6 +167,17 @@
 

drivers/iio/adc/meson_saradc.c line 176

Quoted 9 lines

drivers/iio/adc/meson_saradc.c +7 -0

 #define MESON_SAR_ADC_MAX_FIFO_SIZE                          32
 #define MESON_SAR_ADC_TIMEOUT                                        100 /* ms */
+#define MESON_SAR_ADC_VOLTAGE_AND_TEMP_CHANNEL                       6
+#define MESON_SAR_ADC_TEMP_OFFSET                            27
+
+/* temperature sensor calibration information in eFuse */
+#define MESON_SAR_ADC_EFUSE_BYTES                            4
+#define MESON_SARADC_EFUSE_BYTE3_UPPER_ADC_VAL                       GENMASK(6, 0)
+#define MESON_SARADC_EFUSE_BYTE3_IS_CALIBRATED                       BIT(7)

MESON_SAR_ADC_ prefix for consistency?

drivers/iio/adc/meson_saradc.c line 179

Quoted 3 lines

drivers/iio/adc/meson_saradc.c +3 -0

+
+#define MESON_HHI_DPLL_TOP_0                                 0x318
+#define MESON_HHI_DPLL_TOP_0_TSC_BIT4                                BIT(9)

I guess these do not belog to the SAR ADC at all?

Quoted 16 lines

drivers/iio/adc/meson_saradc.c +3 -2

+
 /* for use with IIO_VAL_INT_PLUS_MICRO */
 #define MILLION                                                      1000000
 

@@ -175,16 +188,27 @@
      .address = _chan,                                               \
      .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |                  \
                              BIT(IIO_CHAN_INFO_AVERAGE_RAW),         \
-     .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |          \
-                             BIT(IIO_CHAN_INFO_CALIBBIAS) |          \
+     .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),           \
+     .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_CALIBBIAS) |       \
                              BIT(IIO_CHAN_INFO_CALIBSCALE),          \
      .datasheet_name = "SAR_ADC_CH"#_chan,                           \
 }
 

drivers/iio/adc/meson_saradc.c line 199

Quoted 7 lines

drivers/iio/adc/meson_saradc.c +3 -4

-/*
- * TODO: the hardware supports IIO_TEMP for channel 6 as well which is
- * currently not supported by this driver.
- */
+#define MESON_SAR_ADC_TEMP_CHAN(_chan) {                             \
+     .type = IIO_TEMP,                                               \
+     .indexed = 0,                                                   \

.indexed = 0 not needed

Quoted 59 lines

drivers/iio/adc/meson_saradc.c +34 -0

+     .channel = _chan,                                               \
+     .address = MESON_SAR_ADC_VOLTAGE_AND_TEMP_CHANNEL,              \
+     .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |                  \
+                             BIT(IIO_CHAN_INFO_AVERAGE_RAW),         \
+     .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |         \
+                                     BIT(IIO_CHAN_INFO_SCALE) |      \
+                                     BIT(IIO_CHAN_INFO_ENABLE),      \
+     .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_CALIBBIAS) |       \
+                             BIT(IIO_CHAN_INFO_CALIBSCALE),          \
+     .datasheet_name = "TEMP_SENSOR",                                \
+}
+
 static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
      MESON_SAR_ADC_CHAN(0),
      MESON_SAR_ADC_CHAN(1),

@@ -197,6 +221,19 @@ static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
      IIO_CHAN_SOFT_TIMESTAMP(8),
 };
 
+static const struct iio_chan_spec meson_sar_adc_and_temp_iio_channels[] = {
+     MESON_SAR_ADC_CHAN(0),
+     MESON_SAR_ADC_CHAN(1),
+     MESON_SAR_ADC_CHAN(2),
+     MESON_SAR_ADC_CHAN(3),
+     MESON_SAR_ADC_CHAN(4),
+     MESON_SAR_ADC_CHAN(5),
+     MESON_SAR_ADC_CHAN(6),
+     MESON_SAR_ADC_CHAN(7),
+     MESON_SAR_ADC_TEMP_CHAN(8),
+     IIO_CHAN_SOFT_TIMESTAMP(9),
+};
+
 enum meson_sar_adc_avg_mode {
      NO_AVERAGING = 0x0,
      MEAN_AVERAGING = 0x1,

@@ -225,6 +262,11 @@ struct meson_sar_adc_param {
      u32                                     bandgap_reg;
      unsigned int                            resolution;
      const struct regmap_config              *regmap_config;
+     u8                                      temperature_trimming_bits;
+     unsigned int                            temperature_multiplier;
+     unsigned int                            temperature_divider;
+     const struct iio_chan_spec              *channels;
+     unsigned int                            num_channels;
 };
 
 struct meson_sar_adc_data {

@@ -246,6 +288,10 @@ 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;
 };
 
 static const struct regmap_config meson_sar_adc_regmap_config_gxbb = {

drivers/iio/adc/meson_saradc.c static void meson_sar_adc_enable_channel(struct iio_dev *indio_dev, · line 438

Quoted 7 lines

drivers/iio/adc/meson_saradc.c +1 -3

@@ -389,9 +435,17 @@ static void meson_sar_adc_enable_channel(struct iio_dev *indio_dev,
                         MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MUX_SEL_MASK,
                         regval);
 
-     if (chan->address == 6)
-             regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
-                                MESON_SAR_ADC_DELTA_10_TEMP_SEL, 0);
+     if (chan->address == MESON_SAR_ADC_VOLTAGE_AND_TEMP_CHANNEL) {

quite repetitive, maybe (just a suggestion)

                u8 val = chan->type == IIO_TEMP ? MESON_SAR_ADC_DELTA_10_TEMP_SEL : 0;
                regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
                                   MESON_SAR_ADC_DELTA_10_TEMP_SEL, val);

drivers/iio/adc/meson_saradc.c static void meson_sar_adc_enable_channel(struct iio_dev *indio_dev, · line 449

Quoted 11 lines

drivers/iio/adc/meson_saradc.c +10 -0

+             if (chan->type == IIO_TEMP)
+                     regmap_update_bits(priv->regmap,
+                                        MESON_SAR_ADC_DELTA_10,
+                                        MESON_SAR_ADC_DELTA_10_TEMP_SEL,
+                                        MESON_SAR_ADC_DELTA_10_TEMP_SEL);
+             else
+                     regmap_update_bits(priv->regmap,
+                                        MESON_SAR_ADC_DELTA_10,
+                                        MESON_SAR_ADC_DELTA_10_TEMP_SEL, 0);
+     }
 }

Channel 6 of the SAR ADC can be switched between two inputs:
SAR_ADC_CH6 input (an actual pad on the SoC) and the signal from the temperature sensor inside the SoC.

To get usable results from the temperature sensor we need to read the corresponding calibration data from the eFuse and pass it to the SAR ADC (bits [3:0]) and (on Meson8b and Meson8m2) to a scratch register in the HHI region.
If the temperature sensor is not calibrated (the eFuse data contains a bit for this) then the driver will return -ENOTSUPP when trying to read the temperature.

This only enables the temperature sensor for the Meson8, Meson8b and Meson8m2 SoCs because on the newer, 64-bit SoCs (GXBB, GXL and GXM) the temperature sensor inside SAR ADC is firmware-controlled (by BL30, we can simply use the SCPI hwmon driver to get the chip temperature).

To keep the devicetree interface backwards compatible we simply skip the temperature sensor initialization if no eFuse nvmem cell is passed via devicetree.

The public documentation for the SAR ADC IP block does not explain how to use the registers to read the temperature. The logic from this patch is based on reading and understanding Amlogic's GPL kernel sources.

Signed-off-by Martin Blumenstingl <[email protected]>

drivers/iio/adc/meson_saradc.c +5 -0

+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_CALIBBIAS) |	\
+				BIT(IIO_CHAN_INFO_CALIBSCALE),		\
+	.datasheet_name = "TEMP_SENSOR",				\
+}
+
 static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
 	MESON_SAR_ADC_CHAN(0),
 	MESON_SAR_ADC_CHAN(1),

@@ -197,6 +221,19 @@ static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
 	IIO_CHAN_SOFT_TIMESTAMP(8),
 };
 

drivers/iio/adc/meson_saradc.c +23 -9

@@ -555,17 +613,31 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
 		break;
 
 	case IIO_CHAN_INFO_SCALE:
-		ret = regulator_get_voltage(priv->vref);
-		if (ret < 0) {
-			dev_err(indio_dev->dev.parent,
-				"failed to get vref voltage: %d\n", ret);
-			return ret;
+		if (chan->type == IIO_VOLTAGE) {
+			ret = regulator_get_voltage(priv->vref);
+			if (ret < 0) {
+				dev_err(indio_dev->dev.parent,
+					"failed to get vref voltage: %d\n",
+					ret);
+				return ret;
+			}
+
+			*val = ret / 1000;
+			*val2 = priv->param->resolution;
+			return IIO_VAL_FRACTIONAL_LOG2;
+		} else if (chan->type == IIO_TEMP) {
+			/* SoC specific multiplier and divider */
+			*val = priv->param->temperature_multiplier;
+			*val2 = priv->param->temperature_divider;
+
+			/* celsius to millicelsius */
+			*val *= 1000;
+
+			return IIO_VAL_FRACTIONAL;
+		} else {
+			return -EINVAL;
 		}
 
-		*val = ret / 1000;
-		*val2 = priv->param->resolution;
-		return IIO_VAL_FRACTIONAL_LOG2;
-
 	case IIO_CHAN_INFO_CALIBBIAS:
 		*val = priv->calibbias;
 		return IIO_VAL_INT;

@@ -575,6 +647,17 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
 		*val2 = priv->calibscale % MILLION;

drivers/iio/adc/meson_saradc.c +49 -0

+		*val = priv->temperature_sensor_calibrated;
+		return IIO_VAL_INT;
+
 	default:
 		return -EINVAL;
 	}

@@ -625,6 +708,77 @@ static int meson_sar_adc_clk_init(struct iio_dev *indio_dev,
 	return 0;
 }
 
+static int meson_sar_adc_temp_sensor_init(struct iio_dev *indio_dev)
+{
+	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
+	u8 *buf, trimming_bits, trimming_mask, upper_adc_val;
+	struct nvmem_cell *temperature_calib;
+	size_t read_len;
+	int ret;
+
+	temperature_calib = devm_nvmem_cell_get(&indio_dev->dev,
+						"temperature_calib");
+	if (IS_ERR(temperature_calib)) {
+		ret = PTR_ERR(temperature_calib);
+
+		/*
+		 * leave the temperature sensor disabled if no calibration data
+		 * was passed via nvmem-cells.
+		 */
+		if (ret == -ENODEV)
+			return 0;
+
+		if (ret != -EPROBE_DEFER)
+			dev_err(indio_dev->dev.parent,
+				"failed to get temperature_calib cell\n");
+
+		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)) {
+		dev_err(indio_dev->dev.parent,
+			"failed to read temperature_calib cell\n");
+		return PTR_ERR(buf);
+	} else if (read_len != MESON_SAR_ADC_EFUSE_BYTES) {
+		kfree(buf);
+		dev_err(indio_dev->dev.parent,
+			"invalid read size of temperature_calib cell\n");

drivers/iio/adc/meson_saradc.c +15 -0

+
+	priv->temperature_sensor_coefficient = buf[2] & trimming_mask;
+
+	upper_adc_val = FIELD_GET(MESON_SARADC_EFUSE_BYTE3_UPPER_ADC_VAL,
+				  buf[3]);
+
+	priv->temperature_sensor_adc_val = buf[2];
+	priv->temperature_sensor_adc_val |= upper_adc_val << BITS_PER_BYTE;
+	priv->temperature_sensor_adc_val >>= trimming_bits;
+
+	kfree(buf);
+
+	return 0;
+}
+

Quoted 11 lines · On Sun, 28 Oct 2018 13:26:24 +0100 Martin Blumenstingl…

Channel 6 of the SAR ADC can be switched between two inputs:
SAR_ADC_CH6 input (an actual pad on the SoC) and the signal from the temperature sensor inside the SoC.

To get usable results from the temperature sensor we need to read the corresponding calibration data from the eFuse and pass it to the SAR ADC (bits [3:0]) and (on Meson8b and Meson8m2) to a scratch register in the HHI region.
If the temperature sensor is not calibrated (the eFuse data contains a bit for this) then the driver will return -ENOTSUPP when trying to read the temperature.

If it is not supported I'd rather not see it at all. Have two channel sets and pick the one without the channel (by all means report the lack of support in the kernel log).

Quoted 14 lines

This only enables the temperature sensor for the Meson8, Meson8b and Meson8m2 SoCs because on the newer, 64-bit SoCs (GXBB, GXL and GXM) the temperature sensor inside SAR ADC is firmware-controlled (by BL30, we can simply use the SCPI hwmon driver to get the chip temperature).

To keep the devicetree interface backwards compatible we simply skip the temperature sensor initialization if no eFuse nvmem cell is passed via devicetree.

The public documentation for the SAR ADC IP block does not explain how to use the registers to read the temperature. The logic from this patch is based on reading and understanding Amlogic's GPL kernel sources.

Quoted 1 line

Signed-off-by Martin Blumenstingl <[email protected]>

Only one significant comment on this (rest looks good to me), what are you using the ENABLE element for in the info_mask?

I 'think' it's an indicator that the temperature sensor reads will always return -ENOSUP? This is non standard so I'd definitely prefer us to do it the way I suggest above.

Thanks,

Jonathan
...

drivers/iio/adc/meson_saradc.c line 206

Quoted 10 lines

drivers/iio/adc/meson_saradc.c +10 -0

+#define MESON_SAR_ADC_TEMP_CHAN(_chan) {                             \
+     .type = IIO_TEMP,                                               \
+     .indexed = 0,                                                   \
+     .channel = _chan,                                               \
+     .address = MESON_SAR_ADC_VOLTAGE_AND_TEMP_CHANNEL,              \
+     .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |                  \
+                             BIT(IIO_CHAN_INFO_AVERAGE_RAW),         \
+     .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |         \
+                                     BIT(IIO_CHAN_INFO_SCALE) |      \
+                                     BIT(IIO_CHAN_INFO_ENABLE),      \

ENABLE?

Quoted 12 lines

drivers/iio/adc/meson_saradc.c +5 -0

+     .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_CALIBBIAS) |       \
+                             BIT(IIO_CHAN_INFO_CALIBSCALE),          \
+     .datasheet_name = "TEMP_SENSOR",                                \
+}
+
 static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
      MESON_SAR_ADC_CHAN(0),
      MESON_SAR_ADC_CHAN(1),

@@ -197,6 +221,19 @@ static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
      IIO_CHAN_SOFT_TIMESTAMP(8),
 };
 

...

Quoted 45 lines

drivers/iio/adc/meson_saradc.c +23 -9

@@ -555,17 +613,31 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
              break;
 
      case IIO_CHAN_INFO_SCALE:
-             ret = regulator_get_voltage(priv->vref);
-             if (ret < 0) {
-                     dev_err(indio_dev->dev.parent,
-                             "failed to get vref voltage: %d\n", ret);
-                     return ret;
+             if (chan->type == IIO_VOLTAGE) {
+                     ret = regulator_get_voltage(priv->vref);
+                     if (ret < 0) {
+                             dev_err(indio_dev->dev.parent,
+                                     "failed to get vref voltage: %d\n",
+                                     ret);
+                             return ret;
+                     }
+
+                     *val = ret / 1000;
+                     *val2 = priv->param->resolution;
+                     return IIO_VAL_FRACTIONAL_LOG2;
+             } else if (chan->type == IIO_TEMP) {
+                     /* SoC specific multiplier and divider */
+                     *val = priv->param->temperature_multiplier;
+                     *val2 = priv->param->temperature_divider;
+
+                     /* celsius to millicelsius */
+                     *val *= 1000;
+
+                     return IIO_VAL_FRACTIONAL;
+             } else {
+                     return -EINVAL;
              }
 
-             *val = ret / 1000;
-             *val2 = priv->param->resolution;
-             return IIO_VAL_FRACTIONAL_LOG2;
-
      case IIO_CHAN_INFO_CALIBBIAS:
              *val = priv->calibbias;
              return IIO_VAL_INT;

@@ -575,6 +647,17 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
              *val2 = priv->calibscale % MILLION;
              return IIO_VAL_INT_PLUS_MICRO;
 

drivers/iio/adc/meson_saradc.c static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev, · line 657

Quoted 8 lines

drivers/iio/adc/meson_saradc.c +8 -0

+     case IIO_CHAN_INFO_OFFSET:
+             *val = DIV_ROUND_CLOSEST(MESON_SAR_ADC_TEMP_OFFSET *
+                                      priv->param->temperature_divider,
+                                      priv->param->temperature_multiplier);
+             *val -= priv->temperature_sensor_adc_val;
+             return IIO_VAL_INT;
+
+     case IIO_CHAN_INFO_ENABLE:

Hmm. This is not a standard use of this attribute. It's normally only used for things that are 'counting' where we want to start and stop a cumulative counter.

Quoted 56 lines

drivers/iio/adc/meson_saradc.c +49 -0

+             *val = priv->temperature_sensor_calibrated;
+             return IIO_VAL_INT;
+
      default:
              return -EINVAL;
      }

@@ -625,6 +708,77 @@ static int meson_sar_adc_clk_init(struct iio_dev *indio_dev,
      return 0;
 }
 
+static int meson_sar_adc_temp_sensor_init(struct iio_dev *indio_dev)
+{
+     struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
+     u8 *buf, trimming_bits, trimming_mask, upper_adc_val;
+     struct nvmem_cell *temperature_calib;
+     size_t read_len;
+     int ret;
+
+     temperature_calib = devm_nvmem_cell_get(&indio_dev->dev,
+                                             "temperature_calib");
+     if (IS_ERR(temperature_calib)) {
+             ret = PTR_ERR(temperature_calib);
+
+             /*
+              * leave the temperature sensor disabled if no calibration data
+              * was passed via nvmem-cells.
+              */
+             if (ret == -ENODEV)
+                     return 0;
+
+             if (ret != -EPROBE_DEFER)
+                     dev_err(indio_dev->dev.parent,
+                             "failed to get temperature_calib cell\n");
+
+             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)) {
+             dev_err(indio_dev->dev.parent,
+                     "failed to read temperature_calib cell\n");
+             return PTR_ERR(buf);
+     } else if (read_len != MESON_SAR_ADC_EFUSE_BYTES) {
+             kfree(buf);
+             dev_err(indio_dev->dev.parent,
+                     "invalid read size of temperature_calib cell\n");

drivers/iio/adc/meson_saradc.c static int meson_sar_adc_clk_init(struct iio_dev *indio_dev, · line 766

Quoted 10 lines

drivers/iio/adc/meson_saradc.c +10 -0

+             return -EINVAL;
+     }
+
+     trimming_bits = priv->param->temperature_trimming_bits;
+     trimming_mask = BIT(trimming_bits) - 1;
+
+     if (buf[3] & MESON_SARADC_EFUSE_BYTE3_IS_CALIBRATED)
+             priv->temperature_sensor_calibrated = true;
+     else
+             priv->temperature_sensor_calibrated = false;

Could just assign?

        priv->temperature_sensor_calibrated =
                buf[3] & MEESON_SARADC_EFUSE_BYTE3_IS_CALIBRATED;

Quoted 8 lines

drivers/iio/adc/meson_saradc.c +8 -0

+
+     priv->temperature_sensor_coefficient = buf[2] & trimming_mask;
+
+     upper_adc_val = FIELD_GET(MESON_SARADC_EFUSE_BYTE3_UPPER_ADC_VAL,
+                               buf[3]);
+
+     priv->temperature_sensor_adc_val = buf[2];
+     priv->temperature_sensor_adc_val |= upper_adc_val << BITS_PER_BYTE;

Quoted 7 lines

drivers/iio/adc/meson_saradc.c +7 -0

+     priv->temperature_sensor_adc_val >>= trimming_bits;
+
+     kfree(buf);
+
+     return 0;
+}
+

...

Quoted 8 lines

drivers/iio/adc/meson_saradc.c static int meson_sar_adc_clk_init(struct iio_dev *indio_dev, · line 766

Quoted 4 lines

drivers/iio/adc/meson_saradc.c +4 -0

+     if (buf[3] & MESON_SARADC_EFUSE_BYTE3_IS_CALIBRATED)
+             priv->temperature_sensor_calibrated = true;
+     else
+             priv->temperature_sensor_calibrated = false;  

Could just assign?

        priv->temperature_sensor_calibrated =
                buf[3] & MEESON_SARADC_EFUSE_BYTE3_IS_CALIBRATED;  

I could change this but (personal preference here) my eyes are not trained to read variable assignments where the value is broken into a new line
looking back at it I could also remove the whole "else" block as "false" is obviously the default value

let me know whether you'd like me to change this, then I'll do that for v2

Quoted 17 lines

Quoted 16 lines

drivers/iio/adc/meson_saradc.c +15 -0

+
+     priv->temperature_sensor_coefficient = buf[2] & trimming_mask;
+
+     upper_adc_val = FIELD_GET(MESON_SARADC_EFUSE_BYTE3_UPPER_ADC_VAL,
+                               buf[3]);
+
+     priv->temperature_sensor_adc_val = buf[2];
+     priv->temperature_sensor_adc_val |= upper_adc_val << BITS_PER_BYTE;
+     priv->temperature_sensor_adc_val >>= trimming_bits;
+
+     kfree(buf);
+
+     return 0;
+}
+  

...

Regards
Martin