Re: [PATCH v8 5/8] iio: adc: adi-axi-adc: set data format

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 13 Dec 2024 18:44:42 +0200
Antoniu Miclaus <antoniu.miclaus@analog.com> wrote:

> Add support for selecting the data format within the AXI ADC ip.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
One trivial comment inline.  If the discussion around David's
question resolves and this is all that is left, I can either tweak
this or we can just decide the long name is fine.

Jonathan

> ---
> changes in v8:
>  - provide inline comments explaning the packet formats as requested in
>    previous review.
>  drivers/iio/adc/adi-axi-adc.c | 46 +++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
> index f6475bc93796..9a3968769512 100644
> --- a/drivers/iio/adc/adi-axi-adc.c
> +++ b/drivers/iio/adc/adi-axi-adc.c
> @@ -45,6 +45,12 @@
>  #define ADI_AXI_ADC_REG_CTRL			0x0044
>  #define    ADI_AXI_ADC_CTRL_DDR_EDGESEL_MASK	BIT(1)
>  
> +#define ADI_AXI_ADC_REG_CNTRL_3			0x004c
> +#define   AD485X_CNTRL_3_CUSTOM_CTRL_PACKET_FORMAT_MSK	GENMASK(1, 0)
I guess this rather long name is straight out of the datasheet / RTL but
maybe..

#define   AD485X_CNTRL_3_PACKET_FORMAT_MSK	GENMASK(1, 0)
Is enough?

> +#define   AD485X_PACKET_FORMAT_20BIT		0x0
> +#define   AD485X_PACKET_FORMAT_24BIT		0x1
> +#define   AD485X_PACKET_FORMAT_32BIT		0x2
> +
>  #define ADI_AXI_ADC_REG_DRP_STATUS		0x0074
>  #define   ADI_AXI_ADC_DRP_LOCKED		BIT(17)
>  
> @@ -312,6 +318,45 @@ static int axi_adc_interface_type_get(struct iio_backend *back,
>  	return 0;
>  }
>  
> +static int axi_adc_data_size_set(struct iio_backend *back, unsigned int size)
> +{
> +	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +	unsigned int val;
> +
> +	switch (size) {
> +	/*
> +	 * There are two different variants of the AXI AD485X IP block, a 16-bit
> +	 * and a 20-bit variant.
> +	 * The 0x0 value (AD485X_PACKET_FORMAT_20BIT) is corresponding also to
> +	 * the 16-bit variant of the IP block.
> +	 */
> +	case 16:
> +	case 20:
> +		val = AD485X_PACKET_FORMAT_20BIT;
> +		break;
> +	case 24:
> +		val = AD485X_PACKET_FORMAT_24BIT;
> +		break;
> +	/*
> +	 * The 0x2 (AD485X_PACKET_FORMAT_32BIT) corresponds only to the 20-bit
> +	 * variant of the IP block. Setting this value properly is ensured by
> +	 * the upper layers of the drivers calling the axi-adc functions.
> +	 * Also, for 16-bit IP block, the 0x2 (AD485X_PACKET_FORMAT_32BIT)
> +	 * value is handled as maximum size available which is 24-bit for this
> +	 * configuration.
> +	 */
> +	case 32:
> +		val = AD485X_PACKET_FORMAT_32BIT;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return regmap_update_bits(st->regmap, ADI_AXI_ADC_REG_CNTRL_3,
> +				  AD485X_CNTRL_3_CUSTOM_CTRL_PACKET_FORMAT_MSK,
> +				  FIELD_PREP(AD485X_CNTRL_3_CUSTOM_CTRL_PACKET_FORMAT_MSK, val));
Yikes.  See suggests for names above.  I think we need to shorted that define
at least a little to improve readability.

> +}
> +
>  static struct iio_buffer *axi_adc_request_buffer(struct iio_backend *back,
>  						 struct iio_dev *indio_dev)
>  {
> @@ -360,6 +405,7 @@ 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,
> +	.data_size_set = axi_adc_data_size_set,
>  	.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),
>  };