iio: adc: adi-axi-adc: add support for AD7606 register writing

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>
Link: https://patch.msgid.link/20250210-wip-bl-ad7606_add_backend_sw_mode-v4-6-160df18b1da7@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 81 insertions, 0 deletions

diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
index 182ad14e4949..766406f45396 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;
@@ -311,6 +322,75 @@ 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, u32 val)
+{
+	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
+
+	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_WR, val);
+	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL,
+		     ADI_AXI_REG_CONFIG_CTRL_WRITE);
+	fsleep(100);
+	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL, 0x00);
+	fsleep(100);
+
+	return 0;
+}
+
+static int axi_adc_raw_read(struct iio_backend *back, u32 *val)
+{
+	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
+
+	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL,
+		     ADI_AXI_REG_CONFIG_CTRL_READ);
+	fsleep(100);
+	regmap_read(st->regmap, ADI_AXI_REG_CONFIG_RD, val);
+	regmap_write(st->regmap, ADI_AXI_REG_CONFIG_CTRL, 0x00);
+	fsleep(100);
+
+	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);
+	int addr;
+
+	guard(mutex)(&st->lock);
+
+	/*
+	 * The address is written on the highest weight byte, and the MSB set
+	 * at 1 indicates a read operation.
+	 */
+	addr = FIELD_PREP(ADI_AXI_REG_ADDRESS_MASK, reg) | ADI_AXI_REG_READ_BIT;
+	axi_adc_raw_write(back, addr);
+	axi_adc_raw_read(back, val);
+
+	/* Write 0x0 on the bus to get back to ADC mode */
+	axi_adc_raw_write(back, 0);
+
+	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 */
+	axi_adc_raw_write(back, 0xaf00);
+
+	buf = FIELD_PREP(ADI_AXI_REG_ADDRESS_MASK, reg) |
+	      FIELD_PREP(ADI_AXI_REG_VALUE_MASK, val);
+	axi_adc_raw_write(back, buf);
+
+	/* Write 0x0 on the bus to get back to ADC mode */
+	axi_adc_raw_write(back, 0);
+
+	return 0;
+}
+
 static void axi_adc_free_buffer(struct iio_backend *back,
 				struct iio_buffer *buffer)
 {
@@ -498,6 +578,7 @@ static const struct axi_adc_info adc_ad7606 = {
 /* 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);