diff options
| author | Martin Blumenstingl <martin.blumenstingl@googlemail.com> | 2017-10-31 21:01:46 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-01-08 16:03:42 +0100 |
| commit | fda29dbac9e6604f8eeb660953a2bef360514dc7 (patch) | |
| tree | ae63afb952771ebc0e318d554fb42e4557faf8d6 /drivers/iio | |
| parent | b9a3589332c2a25fb7edad25a26fcaada3209126 (diff) | |
iio: adc: meson-saradc: fix the clock frequency on Meson8 and Meson8b
GX SoCs use a 1.2 MHz ADC clock, while the older SoCs use a 1.14 MHz
clock.
A comment in the driver from Amlogic's GPL kernel says that it's
running at 1.28 MHz. However, it's actually programming a divider of
20 + 1. With a XTAL clock of 24 MHz this results in a frequency of
1.14 MHz. (their calculation might be based on a 27 MHz XTAL clock,
but this is not what we have on the Meson8 and Meson8b SoCs).
The ADC was still working with the 1.2MHz clock. In my own tests I did
not see a difference between 1.2 and 1.14 MHz (regardless of the clock
frequency used, the ADC results were identical).
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/iio')
| -rw-r--r-- | drivers/iio/adc/meson_saradc.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c index 48fdbb3a061b..24025f179621 100644 --- a/drivers/iio/adc/meson_saradc.c +++ b/drivers/iio/adc/meson_saradc.c @@ -221,6 +221,7 @@ enum meson_sar_adc_chan7_mux_sel { struct meson_sar_adc_data { bool has_bl30_integration; + unsigned long clock_rate; u32 bandgap_reg; unsigned int resolution; const char *name; @@ -683,7 +684,7 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev) return ret; } - ret = clk_set_rate(priv->adc_clk, 1200000); + ret = clk_set_rate(priv->adc_clk, priv->data->clock_rate); if (ret) { dev_err(indio_dev->dev.parent, "failed to set adc clock rate\n"); @@ -856,6 +857,7 @@ static const struct iio_info meson_sar_adc_iio_info = { static const struct meson_sar_adc_data meson_sar_adc_meson8_data = { .has_bl30_integration = false, + .clock_rate = 1150000, .bandgap_reg = MESON_SAR_ADC_DELTA_10, .regmap_config = &meson_sar_adc_regmap_config_meson8, .resolution = 10, @@ -864,6 +866,7 @@ static const struct meson_sar_adc_data meson_sar_adc_meson8_data = { static const struct meson_sar_adc_data meson_sar_adc_meson8b_data = { .has_bl30_integration = false, + .clock_rate = 1150000, .bandgap_reg = MESON_SAR_ADC_DELTA_10, .regmap_config = &meson_sar_adc_regmap_config_meson8, .resolution = 10, @@ -872,6 +875,7 @@ static const struct meson_sar_adc_data meson_sar_adc_meson8b_data = { static const struct meson_sar_adc_data meson_sar_adc_gxbb_data = { .has_bl30_integration = true, + .clock_rate = 1200000, .bandgap_reg = MESON_SAR_ADC_REG11, .regmap_config = &meson_sar_adc_regmap_config_gxbb, .resolution = 10, @@ -880,6 +884,7 @@ static const struct meson_sar_adc_data meson_sar_adc_gxbb_data = { static const struct meson_sar_adc_data meson_sar_adc_gxl_data = { .has_bl30_integration = true, + .clock_rate = 1200000, .bandgap_reg = MESON_SAR_ADC_REG11, .regmap_config = &meson_sar_adc_regmap_config_gxbb, .resolution = 12, @@ -888,6 +893,7 @@ static const struct meson_sar_adc_data meson_sar_adc_gxl_data = { static const struct meson_sar_adc_data meson_sar_adc_gxm_data = { .has_bl30_integration = true, + .clock_rate = 1200000, .bandgap_reg = MESON_SAR_ADC_REG11, .regmap_config = &meson_sar_adc_regmap_config_gxbb, .resolution = 12, |