Re: [PATCH 2/5] iio: adc: adi-axi-adc: add set decimation rate

[David Lechner <dlechner@baylibre.com>]

On 3/24/25 4:07 AM, Pop Ioan Daniel wrote:
> Add support for setting decimation rate.
> 
> Add separate compatible string for the custom AD7405 IP and implement
> the necessary changes.
> 
> Signed-off-by: Pop Ioan Daniel <pop.ioan-daniel@analog.com>
> ---
>  drivers/iio/adc/adi-axi-adc.c | 43 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
> index 766406f45396..0ed609e294ba 100644
> --- a/drivers/iio/adc/adi-axi-adc.c
> +++ b/drivers/iio/adc/adi-axi-adc.c
> @@ -70,6 +70,9 @@
>  #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	0x0424

This is a per-channel register, so expect to have a c parameter times offset
like the other channel registers.

> +#define   ADI_AXI_ADC_DEC_RATE_MASK		GENMASK(15, 0)

Usually, we try to include the register name in these as well even if the name
does get a bit long.

ADI_AXI_ADC_CHAN_USR_CTRL_2_DEC_RATE_N_MASK

> +
>  /* IO Delays */
>  #define ADI_AXI_ADC_REG_DELAY(l)		(0x0800 + (l) * 0x4)
>  #define   AXI_ADC_DELAY_CTRL_MASK		GENMASK(4, 0)
> @@ -232,6 +235,16 @@ static int axi_adc_test_pattern_set(struct iio_backend *back,
>  	}
>  }
>  
> +static int axi_adc_set_dec_rate(struct iio_backend *back,
> +				unsigned int rate)

This needs to take a channel index parameter as well to keep it generic.

> +{
> +	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +

Might be helpful for future users if we add a comment explaining why we are
setting the denominator but not the numerator.

> +	return regmap_update_bits(st->regmap, (ADI_AXI_ADC_REG_CHAN_USR_CTRL_2),
> +					      ADI_AXI_ADC_DEC_RATE_MASK,
> +					      FIELD_PREP(ADI_AXI_ADC_DEC_RATE_MASK, rate));
> +}
> +
>  static int axi_adc_read_chan_status(struct adi_axi_adc_state *st, unsigned int chan,
>  				    unsigned int *status)
>  {
> @@ -465,6 +478,28 @@ static const struct iio_backend_info adi_axi_adc_generic = {
>  	.ops = &adi_axi_adc_ops,
>  };
>  
> +static const struct iio_backend_ops adi_ad7405_ops = {
> +	.enable = axi_adc_enable,
> +	.disable = axi_adc_disable,
> +	.data_format_set = axi_adc_data_format_set,
> +	.chan_enable = axi_adc_chan_enable,
> +	.chan_disable = axi_adc_chan_disable,
> +	.request_buffer = axi_adc_request_buffer,
> +	.free_buffer = axi_adc_free_buffer,
> +	.data_sample_trigger = axi_adc_data_sample_trigger,
> +	.iodelay_set = axi_adc_iodelays_set,
> +	.test_pattern_set = axi_adc_test_pattern_set,
> +	.set_dec_rate = axi_adc_set_dec_rate,
> +	.chan_status = axi_adc_chan_status,
> +	.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),
> +};

As mentioned in my DT bindings patch reply, it looks like this register is part
of the generic AXI ADC IP block, so we shouldn't need to add a chip-specific
struct in this case.

> +
> +static const struct iio_backend_info axi_ad7405 = {
> +	.name = "axi-ad7405",
> +	.ops = &adi_ad7405_ops,
> +};
> +
>  static int adi_axi_adc_probe(struct platform_device *pdev)
>  {
>  	struct adi_axi_adc_state *st;
> @@ -522,7 +557,7 @@ static int adi_axi_adc_probe(struct platform_device *pdev)
>  		return -ENODEV;
>  	}
>  
> -	ret = devm_iio_backend_register(&pdev->dev, &adi_axi_adc_generic, st);
> +	ret = devm_iio_backend_register(&pdev->dev, st->info->backend_info, st);

I'm guessing you haven't rebased on the iio tree recently. This line was already
changed in [1].

[1]: https://web.git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/drivers/iio/adc/adi-axi-adc.c?h=testing&id=7a794e3a0dc5b1df525bf72260b641d70e337784

>  	if (ret)
>  		return dev_err_probe(&pdev->dev, ret,
>  				     "failed to register iio backend\n");
> @@ -575,10 +610,16 @@ static const struct axi_adc_info adc_ad7606 = {
>  	.has_child_nodes = true,
>  };
>  
> +static const struct axi_adc_info adi_axi_ad7405 = {
> +	.version = ADI_AXI_PCORE_VER(10, 0, 'a'),
> +	.backend_info = &axi_ad7405,
> +};
> +
>  /* Match table for of_platform binding */
>  static const struct of_device_id adi_axi_adc_of_match[] = {
>  	{ .compatible = "adi,axi-adc-10.0.a", .data = &adc_generic },
>  	{ .compatible = "adi,axi-ad7606x", .data = &adc_ad7606 },
> +	{ .compatible = "adi,axi-ad7405", .data = &adi_axi_ad7405},
>  	{ /* end of list */ }
>  };
>  MODULE_DEVICE_TABLE(of, adi_axi_adc_of_match);