meson-saradc: add chip temperature support

The 32-bit Meson8 SoC can use the SAR ADC to read the chip temperature. This requires setting the correct TSC (temperature sensor coefficient), which is programmed into the eFuse during the manufacturing process. Meson8b and Meson8m2 are not supported yet because they have a 5-bit TSC and only the first four bits are stored inside the SAR ADC registers.

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

---
 .../devicetree/bindings/iio/adc/amlogic,meson-saradc.txt    | 6 ++++++
 1 file changed, 6 insertions(+)

Documentation/devicetree/bindings/iio/adc/amlogic,meson-saradc.txt +6 -0

index 54b823f3a453..325090e43ce6 100644
@@ -22,6 +22,12 @@ Required properties:
 - vref-supply:	the regulator supply for the ADC reference voltage
 - #io-channel-cells: must be 1, see ../iio-bindings.txt
 
+Optional properties:
+- nvmem-cells:		phandle to the temperature_calib eFuse cells
+- nvmem-cell-names:	if present (to enable the temperature sensor
+			calibration) this must contain "temperature_calib"
+
+
 Example:
 	saradc: adc at 8680 {
 		compatible = "amlogic,meson-gxl-saradc", "amlogic,meson-saradc";

The 32-bit Meson8 SoC can use the SAR ADC to read the chip temperature. This requires setting the correct TSC (temperature sensor coefficient), which is programmed into the eFuse during the manufacturing process. Meson8b and Meson8m2 are not supported yet because they have a 5-bit TSC and only the first four bits are stored inside the SAR ADC registers.

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

---
 .../devicetree/bindings/iio/adc/amlogic,meson-saradc.txt    | 6 ++++++
 1 file changed, 6 insertions(+)

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 registers. If the temperature sensor is not calibrated (the eFuse data contains a bit for this) then the driver will only register the iio_chan_spec's for voltage measurements.

(bits [3:0]) and (on Meson8b and Meson8m2) to a scratch register in the HHI region.

This only enables the temperature sensor for the Meson8 SoC. Meson8b and Meson8m2 SoCs can be supported in the future as well but we first need a way to pass the fifth TSC (temperature sensor coefficient) bit to the HHI register area (apart from that the infrastructure as already implemented for Meson8 can be used). On the 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 | 229 +++++++++++++++++++++++++++++----
 1 file changed, 203 insertions(+), 26 deletions(-)

drivers/iio/adc/meson_saradc.c +203 -26

index 028ccd218f82..26011254ffbc 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>

@@ -165,6 +166,14 @@
 
 #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_SAR_ADC_EFUSE_BYTE3_UPPER_ADC_VAL			GENMASK(6, 0)
+#define MESON_SAR_ADC_EFUSE_BYTE3_IS_CALIBRATED			BIT(7)
+
 /* for use with IIO_VAL_INT_PLUS_MICRO */
 #define MILLION							1000000
 

@@ -175,16 +184,25 @@
 	.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,				\
 }
 
-/*
- * 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,						\
+	.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),	\
+	.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 +215,19 @@ 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 +256,9 @@ 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;
 };
 
 struct meson_sar_adc_data {

@@ -246,6 +280,9 @@ struct meson_sar_adc_priv {
 	struct completion			done;
 	int					calibbias;
 	int					calibscale;
+	bool					temperature_sensor_calibrated;
+	u8					temperature_sensor_coefficient;
+	u16					temperature_sensor_adc_val;
 };
 
 static const struct regmap_config meson_sar_adc_regmap_config_gxbb = {

@@ -389,9 +426,16 @@ 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) {
+		if (chan->type == IIO_TEMP)
+			regval = MESON_SAR_ADC_DELTA_10_TEMP_SEL;
+		else
+			regval = 0;
+
+		regmap_update_bits(priv->regmap,
+				   MESON_SAR_ADC_DELTA_10,
+				   MESON_SAR_ADC_DELTA_10_TEMP_SEL, regval);
+	}
 }
 
 static void meson_sar_adc_set_chan7_mux(struct iio_dev *indio_dev,

@@ -506,8 +550,12 @@ 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 +603,31 @@ 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 +637,13 @@ 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;
+
 	default:
 		return -EINVAL;
 	}

@@ -625,6 +694,65 @@ 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;
+	}
+
+	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;
+
+	priv->temperature_sensor_calibrated =
+		buf[3] & MESON_SAR_ADC_EFUSE_BYTE3_IS_CALIBRATED;
+	priv->temperature_sensor_coefficient = buf[2] & trimming_mask;
+
+	upper_adc_val = FIELD_GET(MESON_SAR_ADC_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 +777,12 @@ 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 +839,29 @@ 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);
+	} 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 +1047,17 @@ 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,
+};
+
+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,
 };
 
 static const struct meson_sar_adc_param meson_sar_adc_gxbb_param = {

@@ -918,12 +1082,12 @@ 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",
 };
 

@@ -1009,9 +1173,6 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 	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);
-
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(base))

@@ -1078,6 +1239,22 @@ 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;
+	}
+
+	if (priv->temperature_sensor_calibrated) {
+		indio_dev->channels = meson_sar_adc_and_temp_iio_channels;
+		indio_dev->num_channels =
+			ARRAY_SIZE(meson_sar_adc_and_temp_iio_channels);
+	} else {
+		indio_dev->channels = meson_sar_adc_iio_channels;
+		indio_dev->num_channels =
+			ARRAY_SIZE(meson_sar_adc_iio_channels);
+	}
+
 	ret = meson_sar_adc_init(indio_dev);
 	if (ret)
 		goto err;

Quoted 4 lines · On Sun, 4 Nov 2018 00:10:24 +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.

Quoted 8 lines

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 registers. If the temperature sensor is not calibrated (the eFuse data contains a bit for this) then the driver will only register the iio_chan_spec's for voltage measurements.

(bits [3:0]) and (on Meson8b and Meson8m2) to a scratch register in the HHI region.

Quoted 13 lines

This only enables the temperature sensor for the Meson8 SoC. Meson8b and Meson8m2 SoCs can be supported in the future as well but we first need a way to pass the fifth TSC (temperature sensor coefficient) bit to the HHI register area (apart from that the infrastructure as already implemented for Meson8 can be used). On the 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.

Quoted 5 lines

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]>

Good detailed explanation. Thanks.

Applied to the togreg branch of iio.git and pushed out as testing for the autobuilders to play with it.

Hi Jonathan,

Quoted 14 lines · Jonathan Cameron

Quoted 10 lines · On Sun, 4 Nov 2018 00:10:24 +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 registers. If the temperature sensor is not calibrated (the eFuse data contains a bit for this) then the driver will only register the iio_chan_spec's for voltage measurements.

Quoted 2 lines

Quoted 2 lines

(bits [3:0]) and (on Meson8b and Meson8m2) to a scratch register in the HHI region.

I missed this "fragment" (I wouldn't call it a sentence) when I sent the patch. the next paragraph already contains an explanation about the TSC on Meson8b and Meson8m2 as well as the HHI register area.
so this paragraph doesn't make any sense and should be removed. do you want me to re-send this patch (or even the whole series) or can you remove it? everything else is fine (I double-checked this time...)

Quoted 14 lines

Quoted 14 lines

This only enables the temperature sensor for the Meson8 SoC. Meson8b and Meson8m2 SoCs can be supported in the future as well but we first need a way to pass the fifth TSC (temperature sensor coefficient) bit to the HHI register area (apart from that the infrastructure as already implemented for Meson8 can be used). On the 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.

Quoted 6 lines

Quoted 5 lines

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]>

Good detailed explanation. Thanks.

you're welcome!
please see my comment above where I have to admit that not all of the description is "good".

Quoted 2 lines

Applied to the togreg branch of iio.git and pushed out as testing for the autobuilders to play with it.

that was quick - thank you!

Regards
Martin