Subject: Re: [PATCH 2/2] iio: adc: stm32: allow to tune analog clock

From: Jonathan Cameron <[email-masked]>
Date: Sat, 9 Nov 2019 12:38:03 +0000

On Sun, 3 Nov 2019 12:30:42 +0000
Jonathan Cameron <[email-masked]> wrote:

> On Mon, 28 Oct 2019 17:11:48 +0100
> Fabrice Gasnier <[email-masked]> wrote:
> 
> > Add new optional dt property to tune analog clock prescaler.
> > Driver looks for optional "st,max-clk-rate-hz", then computes
> > best approximation below that rate, using ADC internal prescaler.
> > 
> > Signed-off-by: Fabrice Gasnier <[email-masked]>  
> If the previous email I wrote on this got to anyone before I hit
> cancel, please ignore. Had completely failed to read the code correctly.
> 
> Anyhow this seems fine to me, but given there are a lot of existing
> clk related bindings I'd like to give a little longer for Rob to
> have a chance to take a look at the binding.
> 
> Give me a poke if I seem to have lost this in a week or so.

Applied to the togreg branch of iio.git. Shortly to be pushed out
as testing for the autobuilders to poke at it.

Thanks,

Jonathan

> 
> Thanks,
> 
> Jonathan
> 
> 
> 
> > ---
> >  drivers/iio/adc/stm32-adc-core.c | 16 +++++++++++++---
> >  1 file changed, 13 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
> > index 20c626c..6537f4f 100644
> > --- a/drivers/iio/adc/stm32-adc-core.c
> > +++ b/drivers/iio/adc/stm32-adc-core.c
> > @@ -79,6 +79,7 @@ struct stm32_adc_priv_cfg {
> >   * @domain:		irq domain reference
> >   * @aclk:		clock reference for the analog circuitry
> >   * @bclk:		bus clock common for all ADCs, depends on part used
> > + * @max_clk_rate:	desired maximum clock rate
> >   * @booster:		booster supply reference
> >   * @vdd:		vdd supply reference
> >   * @vdda:		vdda analog supply reference
> > @@ -95,6 +96,7 @@ struct stm32_adc_priv {
> >  	struct irq_domain		*domain;
> >  	struct clk			*aclk;
> >  	struct clk			*bclk;
> > +	u32				max_clk_rate;
> >  	struct regulator		*booster;
> >  	struct regulator		*vdd;
> >  	struct regulator		*vdda;
> > @@ -141,7 +143,7 @@ static int stm32f4_adc_clk_sel(struct platform_device *pdev,
> >  	}
> >  
> >  	for (i = 0; i < ARRAY_SIZE(stm32f4_pclk_div); i++) {
> > -		if ((rate / stm32f4_pclk_div[i]) <= priv->cfg->max_clk_rate_hz)
> > +		if ((rate / stm32f4_pclk_div[i]) <= priv->max_clk_rate)
> >  			break;
> >  	}
> >  	if (i >= ARRAY_SIZE(stm32f4_pclk_div)) {
> > @@ -230,7 +232,7 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
> >  			if (ckmode)
> >  				continue;
> >  
> > -			if ((rate / div) <= priv->cfg->max_clk_rate_hz)
> > +			if ((rate / div) <= priv->max_clk_rate)
> >  				goto out;
> >  		}
> >  	}
> > @@ -250,7 +252,7 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
> >  		if (!ckmode)
> >  			continue;
> >  
> > -		if ((rate / div) <= priv->cfg->max_clk_rate_hz)
> > +		if ((rate / div) <= priv->max_clk_rate)
> >  			goto out;
> >  	}
> >  
> > @@ -655,6 +657,7 @@ static int stm32_adc_probe(struct platform_device *pdev)
> >  	struct device *dev = &pdev->dev;
> >  	struct device_node *np = pdev->dev.of_node;
> >  	struct resource *res;
> > +	u32 max_rate;
> >  	int ret;
> >  
> >  	if (!pdev->dev.of_node)
> > @@ -731,6 +734,13 @@ static int stm32_adc_probe(struct platform_device *pdev)
> >  	priv->common.vref_mv = ret / 1000;
> >  	dev_dbg(&pdev->dev, "vref+=%dmV\n", priv->common.vref_mv);
> >  
> > +	ret = of_property_read_u32(pdev->dev.of_node, "st,max-clk-rate-hz",
> > +				   &max_rate);
> > +	if (!ret)
> > +		priv->max_clk_rate = min(max_rate, priv->cfg->max_clk_rate_hz);
> > +	else
> > +		priv->max_clk_rate = priv->cfg->max_clk_rate_hz;
> > +
> >  	ret = priv->cfg->clk_sel(pdev, priv);
> >  	if (ret < 0)
> >  		goto err_hw_stop;  
> 

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