diff options
| author | Fabrice Gasnier <fabrice.gasnier@st.com> | 2020-11-06 17:57:26 +0100 |
|---|---|---|
| committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2020-11-14 15:51:13 +0000 |
| commit | 89d1f72570027aa9724f00454f51885e27221413 (patch) | |
| tree | e08c6b1f48848753d18b2adc3b398933371d0699 /drivers/iio | |
| parent | 8dedcc3eee3aceb37832176f0a1b03d5687acda3 (diff) | |
iio: adc: stm32-adc: adapt clock duty cycle for proper operation
For proper operation, STM32 ADC should be used with a clock duty cycle
of 50%, in the range of 49% to 51%. Depending on the clock tree, divider
can be used in case clock duty cycle is out of this range.
In case clk_get_scaled_duty_cycle() returns an error, kindly apply a
divider by default (don't make the probe fail).
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Link: https://lore.kernel.org/r/1604681846-31234-1-git-send-email-fabrice.gasnier@st.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Diffstat (limited to 'drivers/iio')
| -rw-r--r-- | drivers/iio/adc/stm32-adc-core.c | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c index cd870c089182..d64a9e8ff507 100644 --- a/drivers/iio/adc/stm32-adc-core.c +++ b/drivers/iio/adc/stm32-adc-core.c @@ -202,7 +202,7 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev, { u32 ckmode, presc, val; unsigned long rate; - int i, div; + int i, div, duty; /* stm32h7 bus clock is common for all ADC instances (mandatory) */ if (!priv->bclk) { @@ -226,6 +226,11 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev, return -EINVAL; } + /* If duty is an error, kindly use at least /2 divider */ + duty = clk_get_scaled_duty_cycle(priv->aclk, 100); + if (duty < 0) + dev_warn(&pdev->dev, "adc clock duty: %d\n", duty); + for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) { ckmode = stm32h7_adc_ckmodes_spec[i].ckmode; presc = stm32h7_adc_ckmodes_spec[i].presc; @@ -234,6 +239,13 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev, if (ckmode) continue; + /* + * For proper operation, clock duty cycle range is 49% + * to 51%. Apply at least /2 prescaler otherwise. + */ + if (div == 1 && (duty < 49 || duty > 51)) + continue; + if ((rate / div) <= priv->max_clk_rate) goto out; } @@ -246,6 +258,10 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev, return -EINVAL; } + duty = clk_get_scaled_duty_cycle(priv->bclk, 100); + if (duty < 0) + dev_warn(&pdev->dev, "bus clock duty: %d\n", duty); + for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) { ckmode = stm32h7_adc_ckmodes_spec[i].ckmode; presc = stm32h7_adc_ckmodes_spec[i].presc; @@ -254,6 +270,9 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev, if (!ckmode) continue; + if (div == 1 && (duty < 49 || duty > 51)) + continue; + if ((rate / div) <= priv->max_clk_rate) goto out; } |