iio: chemical: bme680: Add support for preheat current

Add functionality to inject a specified amount of current to the heating
plate before the start of the gas measurement to allow the sensor to reach
faster to the requested temperature.

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://patch.msgid.link/20241102131311.36210-5-vassilisamir@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/chemical/bme680.h b/drivers/iio/chemical/bme680.h
index a0a7794..00ab89b 100644 (file)
--- a/drivers/iio/chemical/bme680.h
+++ b/drivers/iio/chemical/bme680.h
@@ -42,6 +42,7 @@
 #define   BME680_RHRANGE_MASK                  GENMASK(5, 4)
 #define BME680_REG_RES_HEAT_VAL                        0x00
 #define   BME680_RSERROR_MASK                  GENMASK(7, 4)
+#define BME680_REG_IDAC_HEAT_0                 0x50
 #define BME680_REG_RES_HEAT_0                  0x5A
 #define BME680_REG_GAS_WAIT_0                  0x64
 #define BME680_ADC_GAS_RES                     GENMASK(15, 6)

diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index 34ce29f..9783953 100644 (file)
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -118,6 +118,7 @@ struct bme680_data {
        u8 oversampling_temp;
        u8 oversampling_press;
        u8 oversampling_humid;
+       u8 preheat_curr_mA;
        u16 heater_dur;
        u16 heater_temp;
 
@@ -214,6 +215,12 @@ static const struct iio_chan_spec bme680_channels[] = {
                },
        },
        IIO_CHAN_SOFT_TIMESTAMP(4),
+       {
+               .type = IIO_CURRENT,
+               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+               .output = 1,
+               .scan_index = -1,
+       },
 };
 
 static int bme680_read_calib(struct bme680_data *data,
@@ -561,6 +568,12 @@ static u8 bme680_calc_heater_dur(u16 dur)
        return durval;
 }
 
+/* Taken from datasheet, section 5.3.3 */
+static u8 bme680_calc_heater_preheat_current(u8 curr)
+{
+       return 8 * curr - 1;
+}
+
 static int bme680_set_mode(struct bme680_data *data, enum bme680_op_mode mode)
 {
        struct device *dev = regmap_get_device(data->regmap);
@@ -659,6 +672,20 @@ static int bme680_chip_config(struct bme680_data *data)
        return 0;
 }
 
+static int bme680_preheat_curr_config(struct bme680_data *data, u8 val)
+{
+       struct device *dev = regmap_get_device(data->regmap);
+       u8 heatr_curr;
+       int ret;
+
+       heatr_curr = bme680_calc_heater_preheat_current(val);
+       ret = regmap_write(data->regmap, BME680_REG_IDAC_HEAT_0, heatr_curr);
+       if (ret < 0)
+               dev_err(dev, "failed to write idac_heat_0 register\n");
+
+       return ret;
+}
+
 static int bme680_gas_config(struct bme680_data *data)
 {
        struct device *dev = regmap_get_device(data->regmap);
@@ -687,6 +714,10 @@ static int bme680_gas_config(struct bme680_data *data)
                return ret;
        }
 
+       ret = bme680_preheat_curr_config(data, data->preheat_curr_mA);
+       if (ret)
+               return ret;
+
        /* Enable the gas sensor and select heater profile set-point 0 */
        ret = regmap_update_bits(data->regmap, BME680_REG_CTRL_GAS_1,
                                 BME680_RUN_GAS_MASK | BME680_NB_CONV_MASK,
@@ -939,6 +970,15 @@ static int bme680_write_raw(struct iio_dev *indio_dev,
 
                return bme680_chip_config(data);
        }
+       case IIO_CHAN_INFO_PROCESSED:
+       {
+               switch (chan->type) {
+               case IIO_CURRENT:
+                       return bme680_preheat_curr_config(data, (u8)val);
+               default:
+                       return -EINVAL;
+               }
+       }
        default:
                return -EINVAL;
        }
@@ -1072,6 +1112,7 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
        data->oversampling_temp = 8;  /* 8X oversampling rate */
        data->heater_temp = 320; /* degree Celsius */
        data->heater_dur = 150;  /* milliseconds */
+       data->preheat_curr_mA = 0;
 
        ret = regmap_write(regmap, BME680_REG_SOFT_RESET, BME680_CMD_SOFTRESET);
        if (ret < 0)