[PATCH v3 5/5] iio: adc: versal-sysmon: add oversampling support

[Salih Erim <salih.erim@amd.com>]

Add support for reading and writing the oversampling ratio through
the IIO oversampling_ratio attribute. The hardware supports averaging
2, 4, 8, or 16 samples, plus a ratio of 1 (no averaging).

Temperature and supply channels share oversampling configuration at
the type level (all temperature channels share one ratio, all supply
channels share another), exposed through info_mask_shared_by_type.

The hardware encoding uses sample_count / 2 in a 4-bit field within
the CONFIG register. Per-channel averaging enable registers must also
be updated to activate or deactivate averaging.

Signed-off-by: Salih Erim <salih.erim@amd.com>
---
Changes in v3:
  - No changes

Changes in v2:
  - EN_AVG per-channel bitmask registers written with all-ones
    instead of boolean 1 when oversampling is enabled
  - EN_AVG write errors propagated to userspace
  - Oversampling limited to satellite temp and supply channels;
    static temp channels do not participate
  - Oversampling exposes actual sample counts (1,2,4,8,16) to
    userspace with internal HW register translation
  - write_raw_get_fmt returns IIO_VAL_INT for oversampling ratio
  - HW encoding documented (sample_count/2, not log2)
  - oversampling_avail is const int[] (type match fix)

 drivers/iio/adc/versal-sysmon-core.c | 136 +++++++++++++++++++++++++++
 drivers/iio/adc/versal-sysmon.h      |  17 ++++
 2 files changed, 153 insertions(+)

diff --git a/drivers/iio/adc/versal-sysmon-core.c b/drivers/iio/adc/versal-sysmon-core.c
index 04977c9c887..7775a4cfa6d 100644
--- a/drivers/iio/adc/versal-sysmon-core.c
+++ b/drivers/iio/adc/versal-sysmon-core.c
@@ -25,6 +25,12 @@
 
 #include "versal-sysmon.h"
 
+/*
+ * Oversampling ratio values exposed to userspace via IIO.
+ * Actual number of samples averaged: 1=none, 2=2x, 4=4x, 8=8x, 16=16x.
+ */
+static const int sysmon_oversampling_avail[] = { 1, 2, 4, 8, 16 };
+
 /* OT and TEMP hysteresis mode bits in SYSMON_TEMP_EV_CFG */
 #define SYSMON_OT_HYST_MASK		BIT(0)
 #define SYSMON_TEMP_HYST_MASK		BIT(1)
@@ -205,6 +211,12 @@ static int sysmon_read_raw(struct iio_dev *indio_dev,
 	unsigned int regval;
 	int ret;
 
+	if (mask == IIO_CHAN_INFO_OVERSAMPLING_RATIO) {
+		*val = (chan->type == IIO_TEMP) ? sysmon->temp_oversampling :
+						 sysmon->supply_oversampling;
+		return IIO_VAL_INT;
+	}
+
 	if (mask != IIO_CHAN_INFO_RAW && mask != IIO_CHAN_INFO_PROCESSED)
 		return -EINVAL;
 
@@ -490,6 +502,117 @@ static int sysmon_write_event_value(struct iio_dev *indio_dev,
 	return -EINVAL;
 }
 
+static int sysmon_set_avg_enable(struct sysmon *sysmon,
+				 u32 base, u32 count, u32 val)
+{
+	int ret;
+
+	for (unsigned int i = 0; i < count; i++) {
+		ret = regmap_write(sysmon->regmap,
+				   base + (i * SYSMON_REG_STRIDE), val);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int sysmon_osr_write(struct sysmon *sysmon, int channel_type, int val)
+{
+	/*
+	 * HW register encoding is sample_count / 2:
+	 * 0=none, 1=2x, 2=4x, 4=8x, 8=16x (not log2-based).
+	 */
+	int hw_val = val >> 1;
+	int ret;
+
+	if (channel_type == IIO_TEMP) {
+		ret = regmap_update_bits(sysmon->regmap, SYSMON_CONFIG,
+					SYSMON_TEMP_SAT_CONFIG_MASK,
+					FIELD_PREP(SYSMON_TEMP_SAT_CONFIG_MASK,
+						   hw_val));
+		if (ret)
+			return ret;
+		ret = sysmon_set_avg_enable(sysmon, SYSMON_TEMP_EN_AVG_BASE,
+					    SYSMON_TEMP_EN_AVG_COUNT,
+					    hw_val ? ~0U : 0);
+		if (ret)
+			return ret;
+	} else if (channel_type == IIO_VOLTAGE) {
+		ret = regmap_update_bits(sysmon->regmap, SYSMON_CONFIG,
+					SYSMON_SUPPLY_CONFIG_MASK,
+					FIELD_PREP(SYSMON_SUPPLY_CONFIG_MASK,
+						   hw_val));
+		if (ret)
+			return ret;
+		ret = sysmon_set_avg_enable(sysmon, SYSMON_SUPPLY_EN_AVG_BASE,
+					    SYSMON_SUPPLY_EN_AVG_COUNT,
+					    hw_val ? ~0U : 0);
+		if (ret)
+			return ret;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int sysmon_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long mask)
+{
+	struct sysmon *sysmon = iio_priv(indio_dev);
+	int i, ret;
+
+	if (mask != IIO_CHAN_INFO_OVERSAMPLING_RATIO)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(sysmon_oversampling_avail); i++) {
+		if (val == sysmon_oversampling_avail[i])
+			break;
+	}
+	if (i == ARRAY_SIZE(sysmon_oversampling_avail))
+		return -EINVAL;
+
+	guard(mutex)(&sysmon->lock);
+
+	ret = sysmon_osr_write(sysmon, chan->type, val);
+	if (ret)
+		return ret;
+
+	if (chan->type == IIO_TEMP)
+		sysmon->temp_oversampling = val;
+	else
+		sysmon->supply_oversampling = val;
+
+	return 0;
+}
+
+static int sysmon_write_raw_get_fmt(struct iio_dev *indio_dev,
+				    struct iio_chan_spec const *chan,
+				    long mask)
+{
+	if (mask == IIO_CHAN_INFO_OVERSAMPLING_RATIO)
+		return IIO_VAL_INT;
+
+	return -EINVAL;
+}
+
+static int sysmon_read_avail(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     const int **vals, int *type,
+			     int *length, long mask)
+{
+	if (mask != IIO_CHAN_INFO_OVERSAMPLING_RATIO)
+		return -EINVAL;
+
+	*vals = sysmon_oversampling_avail;
+	*type = IIO_VAL_INT;
+	*length = ARRAY_SIZE(sysmon_oversampling_avail);
+
+	return IIO_AVAIL_LIST;
+}
+
 static int sysmon_read_label(struct iio_dev *indio_dev,
 			     struct iio_chan_spec const *chan,
 			     char *label)
@@ -502,6 +625,9 @@ static int sysmon_read_label(struct iio_dev *indio_dev,
 
 static const struct iio_info sysmon_iio_info = {
 	.read_raw = sysmon_read_raw,
+	.write_raw = sysmon_write_raw,
+	.write_raw_get_fmt = sysmon_write_raw_get_fmt,
+	.read_avail = sysmon_read_avail,
 	.read_label = sysmon_read_label,
 	.read_event_config = sysmon_read_event_config,
 	.write_event_config = sysmon_write_event_config,
@@ -809,6 +935,10 @@ static int sysmon_parse_fw(struct iio_dev *indio_dev, struct device *dev,
 			.info_mask_separate =
 				BIT(IIO_CHAN_INFO_RAW) |
 				BIT(IIO_CHAN_INFO_PROCESSED),
+			.info_mask_shared_by_type =
+				BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+			.info_mask_shared_by_type_available =
+				BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 			.event_spec = has_irq ?
 				sysmon_supply_events : NULL,
 			.num_event_specs = has_irq ?
@@ -849,6 +979,10 @@ static int sysmon_parse_fw(struct iio_dev *indio_dev, struct device *dev,
 			.info_mask_separate =
 				BIT(IIO_CHAN_INFO_RAW) |
 				BIT(IIO_CHAN_INFO_PROCESSED),
+			.info_mask_shared_by_type =
+				BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+			.info_mask_shared_by_type_available =
+				BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 			.scan_type = {
 				.sign = 's',
 				.realbits = 15,
@@ -902,6 +1036,8 @@ int sysmon_core_probe(struct device *dev, struct regmap *regmap)
 
 	sysmon = iio_priv(indio_dev);
 	sysmon->regmap = regmap;
+	sysmon->temp_oversampling = 1;
+	sysmon->supply_oversampling = 1;
 
 	ret = devm_mutex_init(dev, &sysmon->lock);
 	if (ret)
diff --git a/drivers/iio/adc/versal-sysmon.h b/drivers/iio/adc/versal-sysmon.h
index a78362f95e6..cf69be62709 100644
--- a/drivers/iio/adc/versal-sysmon.h
+++ b/drivers/iio/adc/versal-sysmon.h
@@ -25,11 +25,13 @@ struct regmap;
 #define SYSMON_IMR			0x0048
 #define SYSMON_IER			0x004C
 #define SYSMON_IDR			0x0050
+#define SYSMON_CONFIG			0x0100
 #define SYSMON_TEMP_MAX			0x1030
 #define SYSMON_TEMP_MIN			0x1034
 #define SYSMON_SUPPLY_BASE		0x1040
 #define SYSMON_ALARM_FLAG		0x1018
 #define SYSMON_ALARM_REG		0x1940
+#define SYSMON_SUPPLY_EN_AVG_BASE	0x1958
 #define SYSMON_TEMP_TH_LOW		0x1970
 #define SYSMON_TEMP_TH_UP		0x1974
 #define SYSMON_OT_TH_LOW		0x1978
@@ -41,6 +43,7 @@ struct regmap;
 #define SYSMON_TEMP_MAX_MAX		0x1F90
 #define SYSMON_STATUS_RESET		0x1F94
 #define SYSMON_TEMP_SAT_BASE		0x1FAC
+#define SYSMON_TEMP_EN_AVG_BASE		0x24B4
 #define SYSMON_MAX_REG			0x24C0
 
 /* NPI unlock value written to SYSMON_NPI_LOCK */
@@ -57,6 +60,16 @@ struct regmap;
 /* ISR/IMR temperature and OT alarm mask (bits 9:8) */
 #define SYSMON_TEMP_INTR_MASK		GENMASK(9, 8)
 
+/* Config register: supply oversampling field (bits 17:14) */
+#define SYSMON_SUPPLY_CONFIG_MASK	GENMASK(17, 14)
+
+/* Config register: temp satellite oversampling field (bits 27:24) */
+#define SYSMON_TEMP_SAT_CONFIG_MASK	GENMASK(27, 24)
+
+/* Per-channel averaging enable register counts */
+#define SYSMON_SUPPLY_EN_AVG_COUNT	5
+#define SYSMON_TEMP_EN_AVG_COUNT	2
+
 /* Supply voltage conversion register fields */
 #define SYSMON_MANTISSA_MASK		GENMASK(15, 0)
 #define SYSMON_FMT_MASK			BIT(16)
@@ -85,6 +98,8 @@ struct regmap;
  * @temp_hysteresis: cached DEVICE_TEMP hysteresis in millicelsius
  * @ot_hysteresis: cached OT hysteresis in millicelsius
  * @sysmon_unmask_work: re-enables events after alarm condition clears
+ * @temp_oversampling: current temp oversampling ratio
+ * @supply_oversampling: current supply oversampling ratio
  */
 struct sysmon {
 	struct regmap *regmap;
@@ -101,6 +116,8 @@ struct sysmon {
 	int temp_hysteresis;
 	int ot_hysteresis;
 	struct delayed_work sysmon_unmask_work;
+	unsigned int temp_oversampling;
+	unsigned int supply_oversampling;
 };
 
 int sysmon_core_probe(struct device *dev, struct regmap *regmap);
-- 
2.48.1