On Fri, 6 Nov 2020 17:57:26 +0100 Fabrice Gasnier <[email protected]> wrote:
> 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 <[email protected]> Hi Fabrice, This sounds like it's a fix for a situation in which the device is not currently working? If so, please let me know a fixes tag. Thanks, Jonathan > --- > drivers/iio/adc/stm32-adc-core.c | 21 ++++++++++++++++++++- > 1 file changed, 20 insertions(+), 1 deletion(-) > > diff --git a/drivers/iio/adc/stm32-adc-core.c > b/drivers/iio/adc/stm32-adc-core.c > index cd870c0..d64a9e8 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; > }
