[PATCH v2 5/5] iio: adc: versal-sysmon: add oversampling support

Salih Erim
2026-05-02T11:21:26Z

Add configurable oversampling ratio for supply voltage and temperature
satellite channels. The hardware supports sample counts of 1 (no
averaging), 2, 4, 8, and 16. The userspace-facing values represent
actual sample counts; the driver translates to hardware register
encoding internally.

Oversampling is shared by type: all supply channels share one ratio
and all temperature satellite channels share another. Static
temperature channels (device max/min/max_max/min_min) are hardware-
computed aggregates and do not participate in oversampling.

When oversampling is changed, the driver updates the per-channel
EN_AVG register bitmasks so that all channels in each bank have
hardware averaging enabled or disabled to match the oversampling
configuration.

Register write errors in the per-channel EN_AVG update path are
propagated to userspace.

Signed-off-by: Salih Erim <salih.erim@amd.com>
---
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 | 137 +++++++++++++++++++++++++++
drivers/iio/adc/versal-sysmon.h | 17 ++++
2 files changed, 154 insertions(+)

diff --git a/drivers/iio/adc/versal-sysmon-core.c b/drivers/iio/adc/versal-sysmon-core.c
index 857fe21db7a..9c3ce8f8fdf 100644
--- a/drivers/iio/adc/versal-sysmon-core.c
+++ b/drivers/iio/adc/versal-sysmon-core.c
@@ -19,6 +19,12 @@

#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 bit positions in SYSMON_TEMP_EV_CFG */
#define SYSMON_OT_HYST_BIT BIT(0)
#define SYSMON_TEMP_HYST_BIT BIT(1)
@@ -202,6 +208,12 @@ 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;

@@ -438,6 +450,118 @@ 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)
+{
+ unsigned int i;
+ int ret;
+
+ for (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)
@@ -450,6 +574,9 @@ 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,
@@ -715,6 +842,10 @@ 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_events ?
sysmon_supply_events : NULL,
.num_event_specs = has_events ?
@@ -760,6 +891,10 @@ 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,
@@ -823,6 +958,8 @@ int sysmon_core_probe(struct device *dev, struct regmap *regmap, int irq)
sysmon->indio_dev = indio_dev;
sysmon->regmap = regmap;
sysmon->irq = irq;
+ 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 4f20173de77..9fa7a7486de 100644
--- a/drivers/iio/adc/versal-sysmon.h
+++ b/drivers/iio/adc/versal-sysmon.h
@@ -21,11 +21,13 @@
#define SYSMON_IMR 0x0048
#define SYSMON_IER 0x004C
#define SYSMON_IDR 0x0050
+#define SYSMON_CONFIG 0x0100
#define SYSMON_ALARM_FLAG 0x1018
#define SYSMON_TEMP_MAX 0x1030
#define SYSMON_TEMP_MIN 0x1034
#define SYSMON_SUPPLY_BASE 0x1040
#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
@@ -37,6 +39,7 @@
#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 */
@@ -53,6 +56,16 @@
/* 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 @@
* @masked_temp: currently masked temperature alarm bits
* @temp_mask: temperature interrupt configuration mask
* @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 device *dev;
@@ -98,6 +113,8 @@ struct sysmon {
unsigned int masked_temp;
unsigned int temp_mask;
struct delayed_work sysmon_unmask_work;
+ unsigned int temp_oversampling;
+ unsigned int supply_oversampling;
};

int sysmon_core_probe(struct device *dev, struct regmap *regmap, int irq);
--
2.48.1