iio: adc: aspeed: Support battery sensing.

In ast2600, ADC integrate dividing circuit at last input channel for
battery sensing. This patch use the dts property "battery-sensing" to
enable this feature makes the last channel of each adc can tolerance
higher voltage than reference voltage. The offset interface of ch7 will
be separated when enabling the battery sensing mode.
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Link: https://lore.kernel.org/r/20210922081520.30580-11-billy_tsai@aspeedtech.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/aspeed_adc.c

@@ -87,10 +87,16 @@ struct aspeed_adc_model_data {
 	unsigned int vref_fixed_mv;
 	bool wait_init_sequence;
 	bool need_prescaler;
+	bool bat_sense_sup;
 	u8 scaler_bit_width;
 	unsigned int num_channels;
 };
 
+struct adc_gain {
+	u8 mult;
+	u8 div;
+};
+
 struct aspeed_adc_data {
 	struct device		*dev;
 	const struct aspeed_adc_model_data *model_data;
@@ -104,6 +110,8 @@ struct aspeed_adc_data {
 	int			vref_mv;
 	u32			sample_period_ns;
 	int			cv;
+	bool			battery_sensing;
+	struct adc_gain		battery_mode_gain;
 };
 
 #define ASPEED_CHAN(_idx, _data_reg_addr) {			\
@@ -136,6 +144,27 @@ static const struct iio_chan_spec aspeed_adc_iio_channels[] = {
 	ASPEED_CHAN(15, 0x2E),
 };
 
+#define ASPEED_BAT_CHAN(_idx, _data_reg_addr) {					\
+		.type = IIO_VOLTAGE,						\
+		.indexed = 1,							\
+		.channel = (_idx),						\
+		.address = (_data_reg_addr),					\
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
+				      BIT(IIO_CHAN_INFO_OFFSET),		\
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\
+					    BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
+}
+static const struct iio_chan_spec aspeed_adc_iio_bat_channels[] = {
+	ASPEED_CHAN(0, 0x10),
+	ASPEED_CHAN(1, 0x12),
+	ASPEED_CHAN(2, 0x14),
+	ASPEED_CHAN(3, 0x16),
+	ASPEED_CHAN(4, 0x18),
+	ASPEED_CHAN(5, 0x1A),
+	ASPEED_CHAN(6, 0x1C),
+	ASPEED_BAT_CHAN(7, 0x1E),
+};
+
 static int aspeed_adc_compensation(struct iio_dev *indio_dev)
 {
 	struct aspeed_adc_data *data = iio_priv(indio_dev);
@@ -204,14 +233,39 @@ static int aspeed_adc_read_raw(struct iio_dev *indio_dev,
 			       int *val, int *val2, long mask)
 {
 	struct aspeed_adc_data *data = iio_priv(indio_dev);
+	u32 adc_engine_control_reg_val;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		*val = readw(data->base + chan->address);
+		if (data->battery_sensing && chan->channel == 7) {
+			adc_engine_control_reg_val =
+				readl(data->base + ASPEED_REG_ENGINE_CONTROL);
+			writel(adc_engine_control_reg_val |
+				       FIELD_PREP(ASPEED_ADC_CH7_MODE,
+						  ASPEED_ADC_CH7_BAT) |
+				       ASPEED_ADC_BAT_SENSING_ENABLE,
+			       data->base + ASPEED_REG_ENGINE_CONTROL);
+			/*
+			 * After enable battery sensing mode need to wait some time for adc stable
+			 * Experiment result is 1ms.
+			 */
+			mdelay(1);
+			*val = readw(data->base + chan->address);
+			*val = (*val * data->battery_mode_gain.mult) /
+			       data->battery_mode_gain.div;
+			/* Restore control register value */
+			writel(adc_engine_control_reg_val,
+			       data->base + ASPEED_REG_ENGINE_CONTROL);
+		} else
+			*val = readw(data->base + chan->address);
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_OFFSET:
-		*val = data->cv;
+		if (data->battery_sensing && chan->channel == 7)
+			*val = (data->cv * data->battery_mode_gain.mult) /
+			       data->battery_mode_gain.div;
+		else
+			*val = data->cv;
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_SCALE:
@@ -459,6 +513,23 @@ static int aspeed_adc_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	if (of_find_property(data->dev->of_node, "aspeed,battery-sensing",
+			     NULL)) {
+		if (data->model_data->bat_sense_sup) {
+			data->battery_sensing = 1;
+			if (readl(data->base + ASPEED_REG_ENGINE_CONTROL) &
+			    ASPEED_ADC_BAT_SENSING_DIV) {
+				data->battery_mode_gain.mult = 3;
+				data->battery_mode_gain.div = 1;
+			} else {
+				data->battery_mode_gain.mult = 3;
+				data->battery_mode_gain.div = 2;
+			}
+		} else
+			dev_warn(&pdev->dev,
+				 "Failed to enable battey-sensing mode\n");
+	}
+
 	ret = clk_prepare_enable(data->clk_scaler->clk);
 	if (ret)
 		return ret;
@@ -509,7 +580,9 @@ static int aspeed_adc_probe(struct platform_device *pdev)
 	indio_dev->name = data->model_data->model_name;
 	indio_dev->info = &aspeed_adc_iio_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
-	indio_dev->channels = aspeed_adc_iio_channels;
+	indio_dev->channels = data->battery_sensing ?
+					    aspeed_adc_iio_bat_channels :
+					    aspeed_adc_iio_channels;
 	indio_dev->num_channels = data->model_data->num_channels;
 
 	ret = devm_iio_device_register(data->dev, indio_dev);
@@ -542,6 +615,7 @@ static const struct aspeed_adc_model_data ast2600_adc0_model_data = {
 	.min_sampling_rate = 10000,
 	.max_sampling_rate = 500000,
 	.wait_init_sequence = true,
+	.bat_sense_sup = true,
 	.scaler_bit_width = 16,
 	.num_channels = 8,
 };
@@ -551,6 +625,7 @@ static const struct aspeed_adc_model_data ast2600_adc1_model_data = {
 	.min_sampling_rate = 10000,
 	.max_sampling_rate = 500000,
 	.wait_init_sequence = true,
+	.bat_sense_sup = true,
 	.scaler_bit_width = 16,
 	.num_channels = 8,
 };