linux-kernel - Re: [PATCH 4/7] iio: adc: adi-axi-adc: set data format

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Message-ID: <CAMknhBFu+bD7BDsqtCqt9NoT=z5o9v5+3Zh9RHW=ui=3kFPR0g@mail.gmail.com>
Date: Thu, 26 Sep 2024 11:08:12 +0200
From: David Lechner <dlechner@...libre.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>
Cc: Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Nuno Sa <nuno.sa@...log.com>, 
	Olivier Moysan <olivier.moysan@...s.st.com>, Uwe Kleine-König <ukleinek@...nel.org>, 
	Andy Shevchenko <andy@...nel.org>, Marcelo Schmitt <marcelo.schmitt@...log.com>, 
	Dumitru Ceclan <mitrutzceclan@...il.com>, 
	João Paulo Gonçalves <joao.goncalves@...adex.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Alisa-Dariana Roman <alisadariana@...il.com>, Marius Cristea <marius.cristea@...rochip.com>, 
	Mike Looijmans <mike.looijmans@...ic.nl>, Sergiu Cuciurean <sergiu.cuciurean@...log.com>, 
	Dragos Bogdan <dragos.bogdan@...log.com>, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-pwm@...r.kernel.org
Subject: Re: [PATCH 4/7] iio: adc: adi-axi-adc: set data format

On Mon, Sep 23, 2024 at 12:16 PM Antoniu Miclaus
<antoniu.miclaus@...log.com> wrote:
>
> Add support for selecting the data format within the AXI ADC ip.
>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> ---
>  drivers/iio/adc/adi-axi-adc.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
> index ff48f26e02a3..926a8902c621 100644
> --- a/drivers/iio/adc/adi-axi-adc.c
> +++ b/drivers/iio/adc/adi-axi-adc.c
> @@ -45,6 +45,8 @@
>  #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 ADI_AXI_ADC_REG_DRP_STATUS             0x0074
>  #define   ADI_AXI_ADC_DRP_LOCKED               BIT(17)
>
> @@ -271,6 +273,24 @@ static int axi_adc_interface_type_get(struct iio_backend *back,
>         return 0;
>  }
>
> +static int axi_adc_data_size_set(struct iio_backend *back,
> +                                ssize_t size)
> +{
> +       struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +       unsigned int val;
> +
> +       if (size <= 20)
> +               val = 0;
> +       else if (size <= 24)
> +               val = 1;
> +       else if (size <= 32)
> +               val = 3;
> +       else
> +               return -EINVAL;
> +
> +       return regmap_write(st->regmap, ADI_AXI_ADC_REG_CNTRL_3, val);

http://analogdevicesinc.github.io/hdl/library/axi_ad485x/index.html
says that bit 8 of this register is CRC_EN and bits 7 to 0 are
CUSTOM_CONTROL so we likely need a mask and regmap_write_bits() here.

Also, since the value being written here is CUSTOM_CONTROL, it makes
me wonder if this callback really belongs to adi_axi_adc_generic or if
we need a copy of that specific to the axi_ad485x project to handle
the custom meaning of this value for this family of chips. The
description of CUSTOM_CONTROL in the link is "Select output format
decode mode.(for ADAQ8092: bit 0 - enables digital output randomizer
decode , bit 1 - enables alternate bit polarity decode)." which
doesn't look like what is being done in the function above.

> +}
> +
>  static struct iio_buffer *axi_adc_request_buffer(struct iio_backend *back,
>                                                  struct iio_dev *indio_dev)
>  {
> @@ -308,6 +328,7 @@ static const struct iio_backend_ops adi_axi_adc_generic = {
>         .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,
>  };
>
>  static int adi_axi_adc_probe(struct platform_device *pdev)
> --
> 2.46.0
>