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SubjectRe: [PATCH 2/2] iio: adc: stm32: allow to tune analog clock
On Mon, 28 Oct 2019 17:11:48 +0100
Fabrice Gasnier <fabrice.gasnier@st.com> 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 <fabrice.gasnier@st.com>
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.

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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