diff options
| -rw-r--r-- | drivers/iio/adc/aspeed_adc.c | 54 |
1 files changed, 53 insertions, 1 deletions
diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c index 32f1d6b0942c..9c0ddd237e9e 100644 --- a/drivers/iio/adc/aspeed_adc.c +++ b/drivers/iio/adc/aspeed_adc.c @@ -103,6 +103,7 @@ struct aspeed_adc_data { struct reset_control *rst; int vref_mv; u32 sample_period_ns; + int cv; }; #define ASPEED_CHAN(_idx, _data_reg_addr) { \ @@ -112,7 +113,8 @@ struct aspeed_adc_data { .address = (_data_reg_addr), \ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \ - BIT(IIO_CHAN_INFO_SAMP_FREQ), \ + BIT(IIO_CHAN_INFO_SAMP_FREQ) | \ + BIT(IIO_CHAN_INFO_OFFSET), \ } static const struct iio_chan_spec aspeed_adc_iio_channels[] = { @@ -134,6 +136,51 @@ static const struct iio_chan_spec aspeed_adc_iio_channels[] = { ASPEED_CHAN(15, 0x2E), }; +static int aspeed_adc_compensation(struct iio_dev *indio_dev) +{ + struct aspeed_adc_data *data = iio_priv(indio_dev); + u32 index, adc_raw = 0; + u32 adc_engine_control_reg_val; + + adc_engine_control_reg_val = + readl(data->base + ASPEED_REG_ENGINE_CONTROL); + adc_engine_control_reg_val &= ~ASPEED_ADC_OP_MODE; + adc_engine_control_reg_val |= + (FIELD_PREP(ASPEED_ADC_OP_MODE, ASPEED_ADC_OP_MODE_NORMAL) | + ASPEED_ADC_ENGINE_ENABLE); + /* + * Enable compensating sensing: + * After that, the input voltage of ADC will force to half of the reference + * voltage. So the expected reading raw data will become half of the max + * value. We can get compensating value = 0x200 - ADC read raw value. + * It is recommended to average at least 10 samples to get a final CV. + */ + writel(adc_engine_control_reg_val | ASPEED_ADC_CTRL_COMPENSATION | + ASPEED_ADC_CTRL_CHANNEL_ENABLE(0), + data->base + ASPEED_REG_ENGINE_CONTROL); + /* + * After enable compensating sensing mode need to wait some time for ADC stable + * Experiment result is 1ms. + */ + mdelay(1); + + for (index = 0; index < 16; index++) { + /* + * Waiting for the sampling period ensures that the value acquired + * is fresh each time. + */ + ndelay(data->sample_period_ns); + adc_raw += readw(data->base + aspeed_adc_iio_channels[0].address); + } + adc_raw >>= 4; + data->cv = BIT(ASPEED_RESOLUTION_BITS - 1) - adc_raw; + writel(adc_engine_control_reg_val, + data->base + ASPEED_REG_ENGINE_CONTROL); + dev_dbg(data->dev, "Compensating value = %d\n", data->cv); + + return 0; +} + static int aspeed_adc_set_sampling_rate(struct iio_dev *indio_dev, u32 rate) { struct aspeed_adc_data *data = iio_priv(indio_dev); @@ -163,6 +210,10 @@ static int aspeed_adc_read_raw(struct iio_dev *indio_dev, *val = readw(data->base + chan->address); return IIO_VAL_INT; + case IIO_CHAN_INFO_OFFSET: + *val = data->cv; + return IIO_VAL_INT; + case IIO_CHAN_INFO_SCALE: *val = data->vref_mv; *val2 = ASPEED_RESOLUTION_BITS; @@ -448,6 +499,7 @@ static int aspeed_adc_probe(struct platform_device *pdev) return ret; } + aspeed_adc_compensation(indio_dev); /* Start all channels in normal mode. */ adc_engine_control_reg_val = readl(data->base + ASPEED_REG_ENGINE_CONTROL); |