linux-kernel - Re: [PATCH v2 2/4] iio: adc: adi-axi-adc: add set decimation rate

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Message-ID: <37ae4941-da7e-4298-8269-b5faf29fffdd@baylibre.com>
Date: Thu, 8 May 2025 11:45:50 -0500
From: David Lechner <dlechner@...libre.com>
To: Pop Ioan Daniel <pop.ioan-daniel@...log.com>,
 Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Sergiu Cuciurean <sergiu.cuciurean@...log.com>,
 Dragos Bogdan <dragos.bogdan@...log.com>,
 Antoniu Miclaus <antoniu.miclaus@...log.com>,
 Olivier Moysan <olivier.moysan@...s.st.com>,
 Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Matti Vaittinen <mazziesaccount@...il.com>,
 Tobias Sperling <tobias.sperling@...ting.com>,
 Marcelo Schmitt <marcelo.schmitt@...log.com>,
 Alisa-Dariana Roman <alisadariana@...il.com>,
 Esteban Blanc <eblanc@...libre.com>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] iio: adc: adi-axi-adc: add set decimation rate

On 5/8/25 7:30 AM, Pop Ioan Daniel wrote:
> Add support for setting decimation rate.
> 
> Signed-off-by: Pop Ioan Daniel <pop.ioan-daniel@...log.com>
> ---
> changes in v2:
>  - update ADI_AXI_ADC_REG_CHAN_USR_CTRL_2 register in a per-channel register
>  - rename ADI_AXI_ADC_DEC_RATE_MASK in
>    ADI_AXI_ADC_CHAN_USR_CTRL_2_DEC_RATE_N_MASK
>  - add channel index parameter to keep axi_adc_set_dec_rate generic
>  - remove ad7405 chip-specific struct
>  drivers/iio/adc/adi-axi-adc.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
> index 9e8c30230791..33eb8f337e0b 100644
> --- a/drivers/iio/adc/adi-axi-adc.c
> +++ b/drivers/iio/adc/adi-axi-adc.c
> @@ -80,6 +80,9 @@
>  #define ADI_AXI_ADC_REG_CHAN_CTRL_3(c)		(0x0418 + (c) * 0x40)
>  #define   ADI_AXI_ADC_CHAN_PN_SEL_MASK		GENMASK(19, 16)
>  
> +#define ADI_AXI_ADC_REG_CHAN_USR_CTRL_2(c)	(0x0424 + (c) * 0x40)
> +#define   ADI_AXI_ADC_CHAN_USR_CTRL_2_DEC_RATE_N_MASK		GENMASK(15, 0)
> +
>  /* IO Delays */
>  #define ADI_AXI_ADC_REG_DELAY(l)		(0x0800 + (l) * 0x4)
>  #define   AXI_ADC_DELAY_CTRL_MASK		GENMASK(4, 0)
> @@ -242,6 +245,17 @@ static int axi_adc_test_pattern_set(struct iio_backend *back,
>  	}
>  }
>  
> +static int axi_adc_set_dec_rate(struct iio_backend *back, unsigned int chan,
> +				unsigned int rate)
> +{
> +	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +
> +	return regmap_update_bits(st->regmap,
> +				  ADI_AXI_ADC_REG_CHAN_USR_CTRL_2(chan),
> +				  ADI_AXI_ADC_CHAN_USR_CTRL_2_DEC_RATE_N_MASK,
> +				  FIELD_PREP(ADI_AXI_ADC_CHAN_USR_CTRL_2_DEC_RATE_N_MASK, rate));

Rate is getting a bit far past 80 chars, so would be nice to wrap that line.

> +}
> +
>  static int axi_adc_read_chan_status(struct adi_axi_adc_state *st, unsigned int chan,
>  				    unsigned int *status)
>  {
> @@ -550,6 +564,7 @@ static const struct iio_backend_ops adi_axi_adc_ops = {
>  	.test_pattern_set = axi_adc_test_pattern_set,
>  	.chan_status = axi_adc_chan_status,
>  	.interface_type_get = axi_adc_interface_type_get,
> +	.oversampling_ratio_set = axi_adc_set_dec_rate,

Would make more sense if function was named axi_adc_oversampling_ratio_set.
(Making the names match exactly (with namespace prefix added) make less info
you have to hold in your head when reading the driver.)

>  	.debugfs_reg_access = iio_backend_debugfs_ptr(axi_adc_reg_access),
>  	.debugfs_print_chan_status = iio_backend_debugfs_ptr(axi_adc_debugfs_print_chan_status),
>  };