[PATCH v3 2/4] iio: adc: Enable multiple consecutive channels based on model data

[Billy Tsai <billy_tsai@aspeedtech.com>]

Add helpers to generate channel masks and enable multiple ADC channels
according to the device model's channel count.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
 drivers/iio/adc/aspeed_adc.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
index 8eebaa3dc534..3ff24474f394 100644
--- a/drivers/iio/adc/aspeed_adc.c
+++ b/drivers/iio/adc/aspeed_adc.c
@@ -123,6 +123,24 @@ struct aspeed_adc_data {
 	struct adc_gain		battery_mode_gain;
 };
 
+/*
+ * Enable multiple consecutive channels starting from channel 0.
+ * This creates a bitmask for channels 0 to (num_channels - 1).
+ * For example: num_channels=3 creates mask 0x0007 (channels 0,1,2)
+ */
+static inline u32 aspeed_adc_channels_mask(unsigned int num_channels)
+{
+	if (num_channels > 16)
+		return GENMASK(15, 0);
+
+	return BIT(num_channels) - 1;
+}
+
+static inline unsigned int aspeed_adc_get_active_channels(const struct aspeed_adc_data *data)
+{
+	return data->model_data->num_channels;
+}
+
 #define ASPEED_CHAN(_idx, _data_reg_addr) {			\
 	.type = IIO_VOLTAGE,					\
 	.indexed = 1,						\
@@ -612,7 +630,9 @@ static int aspeed_adc_probe(struct platform_device *pdev)
 	/* Start all channels in normal mode. */
 	adc_engine_control_reg_val =
 		readl(data->base + ASPEED_REG_ENGINE_CONTROL);
-	adc_engine_control_reg_val |= ASPEED_ADC_CTRL_CHANNEL;
+	FIELD_MODIFY(ASPEED_ADC_CTRL_CHANNEL, &adc_engine_control_reg_val,
+		     aspeed_adc_channels_mask(aspeed_adc_get_active_channels(data)));
+
 	writel(adc_engine_control_reg_val,
 	       data->base + ASPEED_REG_ENGINE_CONTROL);
 

-- 
2.34.1