Re: [PATCH v2] staging: iio: adc: ad7192: fix external frequency setting

[Jonathan Cameron <jic23@jic23.retrosnub.co.uk>]

On Thu, 18 Jan 2018 16:44:49 +0200
<alexandru.ardelean@analog.com> wrote:

> From: Alexandru Ardelean <alexandru.ardelean@analog.com>
> 
> The external clock frequency was set only when selecting
> the internal clock, which is fixed at 4.9152 Mhz.
> 
> This is incorrect, since it should be set when any of
> the external clock or crystal settings is selected.
> 
> Added range validation for the validating the external
> (crystal/clock) frequency setting.
> Valid values are between 2.4576 and 5.12 Mhz.
> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
A couple of minor points inline..

Jonathan

> ---
> 
> Changes since v1:
>  * assign frequency from `pdata->ext_clk_hz`, not `pdata->ext_clk_hz`
Err, my eye sight may be failing me, but those two look the same...

>  * check frequency range for both crystal & (external) clock
>  * print error if clock range is invalid
>  * patch was split away from patch-series (for device-tree bindings)
> 
>  drivers/staging/iio/adc/ad7192.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/iio/adc/ad7192.c b/drivers/staging/iio/adc/ad7192.c
> index aebbc3b58194..6d110f817b4e 100644
> --- a/drivers/staging/iio/adc/ad7192.c
> +++ b/drivers/staging/iio/adc/ad7192.c
> @@ -141,6 +141,8 @@
>  #define AD7192_GPOCON_P1DAT	BIT(1) /* P1 state */
>  #define AD7192_GPOCON_P0DAT	BIT(0) /* P0 state */
>  
> +#define AD7192_EXT_FREQ_MHZ_MIN	2457600
> +#define AD7192_EXT_FREQ_MHZ_MAX	5120000
>  #define AD7192_INT_FREQ_MHZ	4915200
>  
>  /* NOTE:
> @@ -217,6 +219,12 @@ static int ad7192_calibrate_all(struct ad7192_state *st)
>  				ARRAY_SIZE(ad7192_calib_arr));
>  }
>  
> +static inline bool ad7192_valid_external_frequency(u32 freq)
> +{
> +	return (freq >= AD7192_EXT_FREQ_MHZ_MIN &&
> +		freq <= AD7192_EXT_FREQ_MHZ_MAX);
> +}
> +
>  static int ad7192_setup(struct ad7192_state *st,
>  			const struct ad7192_platform_data *pdata)
>  {
> @@ -244,17 +252,19 @@ static int ad7192_setup(struct ad7192_state *st,
>  			 id);
>  
>  	switch (pdata->clock_source_sel) {
> -	case AD7192_CLK_EXT_MCLK1_2:
> -	case AD7192_CLK_EXT_MCLK2:
> -		st->mclk = AD7192_INT_FREQ_MHZ;
> -		break;
>  	case AD7192_CLK_INT:
>  	case AD7192_CLK_INT_CO:
> -		if (pdata->ext_clk_hz)
> -			st->mclk = pdata->ext_clk_hz;
> -		else
> -			st->mclk = AD7192_INT_FREQ_MHZ;
> +		st->mclk = AD7192_INT_FREQ_MHZ;
>  		break;
> +	case AD7192_CLK_EXT_MCLK1_2:
> +	case AD7192_CLK_EXT_MCLK2:
> +		if (ad7192_valid_external_frequency(pdata->ext_clk_hz)) {
> +			st->mclk = pdata->ext_clk_hz;
> +			break;
> +		}
> +		dev_err(&st->sd.spi->dev, "Invalid frequency setting %u\n",
> +			pdata->ext_clk_hz);
> +		/* FALLTHROUGH */
Whilst it saves lines of code, the clarity of the code is reduced.
Just put
ret = -EINVAL;
break;
>  	default:
>  		ret = -EINVAL;
>  		goto out;