Re: [PATCH v3 07/10] iio: adc: adi-axi-adc: add support for AD7606 register writing

[David Lechner <dlechner@baylibre.com>]

On 1/29/25 5:03 AM, Angelo Dureghello wrote:
> From: Guillaume Stols <gstols@baylibre.com>
> 
> Since we must access the bus parallel bus using a custom procedure,
> let's add a specialized compatible, and define specialized callbacks for
> writing the registers using the parallel interface.
> 
> Signed-off-by: Guillaume Stols <gstols@baylibre.com>
> Co-developed-by: Angelo Dureghello <adureghello@baylibre.com>
> Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
> ---
>  drivers/iio/adc/adi-axi-adc.c | 100 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 100 insertions(+)
> 
> diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
> index 0923565cf5bb..aaeb445a8a3e 100644
> --- a/drivers/iio/adc/adi-axi-adc.c
> +++ b/drivers/iio/adc/adi-axi-adc.c
> @@ -27,6 +27,7 @@
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/iio.h>
>  
> +#include "ad7606_bus_iface.h"
>  /*
>   * Register definitions:
>   *   https://wiki.analog.com/resources/fpga/docs/axi_adc_ip#register_map
> @@ -73,6 +74,12 @@
>  #define ADI_AXI_ADC_REG_DELAY(l)		(0x0800 + (l) * 0x4)
>  #define   AXI_ADC_DELAY_CTRL_MASK		GENMASK(4, 0)
>  
> +#define ADI_AXI_REG_CONFIG_WR			0x0080
> +#define ADI_AXI_REG_CONFIG_RD			0x0084
> +#define ADI_AXI_REG_CONFIG_CTRL			0x008c
> +#define   ADI_AXI_REG_CONFIG_CTRL_READ		0x03
> +#define   ADI_AXI_REG_CONFIG_CTRL_WRITE		0x01
> +
>  #define ADI_AXI_ADC_MAX_IO_NUM_LANES		15
>  
>  #define ADI_AXI_REG_CHAN_CTRL_DEFAULTS		\
> @@ -80,6 +87,10 @@
>  	 ADI_AXI_REG_CHAN_CTRL_FMT_EN |		\
>  	 ADI_AXI_REG_CHAN_CTRL_ENABLE)
>  
> +#define ADI_AXI_REG_READ_BIT			0x8000
> +#define ADI_AXI_REG_ADDRESS_MASK		0xff00
> +#define ADI_AXI_REG_VALUE_MASK			0x00ff
> +
>  struct axi_adc_info {
>  	unsigned int version;
>  	const struct iio_backend_info *backend_info;
> @@ -313,6 +324,81 @@ static struct iio_buffer *axi_adc_request_buffer(struct iio_backend *back,
>  	return iio_dmaengine_buffer_setup(st->dev, indio_dev, dma_name);
>  }
>  
> +static int axi_adc_raw_write(struct iio_backend *back, void *buf, unsigned int len)
> +{
> +	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +	u32 data;
> +
> +	data = *(u32 *)(buf);

Hmm... could result in unaligned access and len is not used. Can we just have
`u32 val` as the parameter instead of buf and len?

> +
> +	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_WR, data);
> +	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL,
> +		     ADI_AXI_REG_CONFIG_CTRL_WRITE);
> +	usleep_range(50, 100);

Use fsleep().

> +	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL, 0x00);
> +	usleep_range(50, 100);
> +
> +	return 0;
> +}
> +
> +static int axi_adc_raw_read(struct iio_backend *back, void *buf, unsigned int len)
> +{
> +	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +	u32 *bdata = buf;

ditto (about buf and len)

> +
> +	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL,
> +		     ADI_AXI_REG_CONFIG_CTRL_READ);
> +	usleep_range(50, 100);
> +	regmap_read(st->regmap, ADI_AXI_REG_CONFIG_RD, bdata);
> +	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL, 0x00);
> +	usleep_range(50, 100);

ditto (fsleep)

> +
> +	return 0;
> +}
> +
> +static int ad7606_bus_reg_read(struct iio_backend *back, u32 reg, u32 *val)
> +{
> +	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +	u32 buf;
> +
> +	guard(mutex)(&st->lock);
> +
> +	/*
> +	 * The address is written on the highest weight byte, and the MSB set
> +	 * at 1 indicates a read operation.
> +	 */
> +	buf = FIELD_PREP(ADI_AXI_REG_ADDRESS_MASK, reg) | ADI_AXI_REG_READ_BIT;
> +	axi_adc_raw_write(back, &buf, sizeof(buf));
> +	axi_adc_raw_read(back, val, 4);
> +
> +	/* Write 0x0 on the bus to get back to ADC mode */
> +	buf = 0;
> +	axi_adc_raw_write(back, &buf, sizeof(buf));
> +	return 0;
> +}
> +
> +static int ad7606_bus_reg_write(struct iio_backend *back, u32 reg, u32 val)
> +{
> +	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
> +	u32 buf;
> +
> +	guard(mutex)(&st->lock);
> +
> +	/* Write any register to switch to register mode */
> +	buf = 0xaf00;
> +	axi_adc_raw_write(back, &buf, sizeof(buf));
> +
> +	buf = FIELD_PREP(ADI_AXI_REG_ADDRESS_MASK, reg) |
> +	      FIELD_PREP(ADI_AXI_REG_VALUE_MASK, val);
> +	axi_adc_raw_write(back, &buf, sizeof(buf));
> +
> +	/* Write 0x0 on the bus to get back to ADC mode */
> +	buf = 0;
> +	axi_adc_raw_write(back, &buf, sizeof(buf));
> +
> +	return 0;
> +}
> +
>  static void axi_adc_free_buffer(struct iio_backend *back,
>  				struct iio_buffer *buffer)
>  {
> @@ -484,9 +570,23 @@ static const struct axi_adc_info adc_generic = {
>  	.backend_info = &adi_axi_adc_generic,
>  };
>  
> +static const struct ad7606_platform_data ad7606_pdata = {
> +	.bus_reg_read = ad7606_bus_reg_read,
> +	.bus_reg_write = ad7606_bus_reg_write,
> +};
> +
> +static const struct axi_adc_info adc_ad7606 = {
> +	.version = ADI_AXI_PCORE_VER(10, 0, 'a'),

Is this the actual current version we are testing with? IIRC there were some
changes made recently for this variant of the IP block so would be best to make
sure we have the latest version here since older versions might not be working.

> +	.backend_info = &adi_axi_adc_generic,
> +	.bus_controller = true,
> +	.pdata = &ad7606_pdata,
> +	.pdata_sz = sizeof(ad7606_pdata),
> +};
> +
>  /* 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 },
>  	{ /* end of list */ }
>  };
>  MODULE_DEVICE_TABLE(of, adi_axi_adc_of_match);
>