iio: adc: adi-axi-adc: implement backend debugfs interface

Implement debugfs options to read/write registers and print the channel
status into a buffer (so we may know better the cause for errors) .
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240802-dev-iio-backend-add-debugfs-v2-6-4cb62852f0d0@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/adi-axi-adc.c

@@ -61,6 +61,10 @@
 
 #define ADI_AXI_ADC_REG_CHAN_STATUS(c)		(0x0404 + (c) * 0x40)
 #define   ADI_AXI_ADC_CHAN_STAT_PN_MASK		GENMASK(2, 1)
+/* out of sync */
+#define   ADI_AXI_ADC_CHAN_STAT_PN_OOS		BIT(1)
+/* spurious out of sync */
+#define   ADI_AXI_ADC_CHAN_STAT_PN_ERR		BIT(2)
 
 #define ADI_AXI_ADC_REG_CHAN_CTRL_3(c)		(0x0418 + (c) * 0x40)
 #define   ADI_AXI_ADC_CHAN_PN_SEL_MASK		GENMASK(19, 16)
@@ -246,6 +250,30 @@ static int axi_adc_chan_status(struct iio_backend *back, unsigned int chan,
 	return 0;
 }
 
+static int axi_adc_debugfs_print_chan_status(struct iio_backend *back,
+					     unsigned int chan, char *buf,
+					     size_t len)
+{
+	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
+	u32 val;
+	int ret;
+
+	ret = axi_adc_read_chan_status(st, chan, &val);
+	if (ret)
+		return ret;
+
+	/*
+	 * PN_ERR is cleared in case out of sync is set. Hence, no point in
+	 * checking both bits.
+	 */
+	if (val & ADI_AXI_ADC_CHAN_STAT_PN_OOS)
+		return scnprintf(buf, len, "CH%u: Out of Sync.\n", chan);
+	if (val & ADI_AXI_ADC_CHAN_STAT_PN_ERR)
+		return scnprintf(buf, len, "CH%u: Spurious Out of Sync.\n", chan);
+
+	return scnprintf(buf, len, "CH%u: OK.\n", chan);
+}
+
 static int axi_adc_chan_enable(struct iio_backend *back, unsigned int chan)
 {
 	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
@@ -280,6 +308,17 @@ static void axi_adc_free_buffer(struct iio_backend *back,
 	iio_dmaengine_buffer_free(buffer);
 }
 
+static int axi_adc_reg_access(struct iio_backend *back, unsigned int reg,
+			      unsigned int writeval, unsigned int *readval)
+{
+	struct adi_axi_adc_state *st = iio_backend_get_priv(back);
+
+	if (readval)
+		return regmap_read(st->regmap, reg, readval);
+
+	return regmap_write(st->regmap, reg, writeval);
+}
+
 static const struct regmap_config axi_adc_regmap_config = {
 	.val_bits = 32,
 	.reg_bits = 32,
@@ -298,6 +337,8 @@ static const struct iio_backend_ops adi_axi_adc_ops = {
 	.iodelay_set = axi_adc_iodelays_set,
 	.test_pattern_set = axi_adc_test_pattern_set,
 	.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),
 };
 
 static const struct iio_backend_info adi_axi_adc_generic = {