[PATCH v8 00/10] iio: pressure: dps310: FIFO and triggered buffer support

[PATCH v8 00/10] iio: pressure: dps310: FIFO and triggered buffer support

[Rupesh Majhi]

Jonathan's review fixes on v7. Same functionality, except the flush hook,
which now holds the device mode while it drains.

Since v7:
 - the timestamp scan index lands in patch 5, where the enum is
 - the FIFO drain reads with one loop counter, declarations split
 - dps310_fifo_hold_free() is gone. It was a bare kfree() once the
   clearing went, and the alloc side sets the fields instead
 - the flush hook holds the mode across the drain, so a concurrent
   buffer disable cannot free active_scan_mask under it. Found by
   Sashiko on v7. Done with IIO_DEV_GUARD_CURRENT_MODE() and not the
   buffer mode claim, which patch 10 warns on, see the reply on 9/10

Retested on a DPS310 on a BeagleBone Black: six of six buffer enables
produce data, and 64 scan reads come back whole at watermark 1, 8 and 24.
Built with clang 23 and CONFIG_WARN_CONTEXT_ANALYSIS, no warnings.

Patch 10 opts into clang context analysis and comes last, so it can be
dropped alone.

Deferred to a cleanup series: min_t() to min(), 1000 to KILO,
30 * USEC_PER_MSEC, David's define sort, c00/c10 via get_unaligned_be24().

Rupesh Majhi (10):
  iio: pressure: dps310: fix CFG_REG bit definitions
  iio: pressure: dps310: use a local device pointer in probe
  iio: pressure: dps310: use get_unaligned_be24() for the 24-bit results
  iio: pressure: dps310: take the lock once per raw read
  iio: pressure: dps310: add triggered buffer support
  iio: core: add an accessor for scan_timestamp
  iio: pressure: dps310: read buffered samples from the hardware FIFO
  iio: pressure: dps310: derive the drain interval from the watermark
  iio: pressure: dps310: implement .hwfifo_flush_to_buffer()
  iio: pressure: dps310: check the lock markings with context analysis

 drivers/iio/pressure/Kconfig  |   2 +
 drivers/iio/pressure/Makefile |   2 +
 drivers/iio/pressure/dps310.c | 726 ++++++++++++++++++++++++++++++----
 include/linux/iio/iio.h       |   9 +
 4 files changed, 652 insertions(+), 87 deletions(-)

-- 
2.43.0

[PATCH v8 01/10] iio: pressure: dps310: fix CFG_REG bit definitions

[Rupesh Majhi]

Driver defines them as BIT(4), BIT(5) and BIT(6). Per datasheet P_SHIFT
is bit 2, FIFO_EN is bit 1 and SPI_MODE is bit 0.

Only P_SHIFT has a user. dps310_set_pres_precision() sets it at
oversampling 16 or above, so with wrong bit the result register is never
shifted and stops matching the scale factor compensation divides by.
in_pressure_input returns -ERANGE at oversampling 16, 32 and 64.

FIFO_EN needed by FIFO support later in this series.

Fixes: ba6ec48e76bc ("iio: Add driver for Infineon DPS310")
Fixes: d711a3c7dc82 ("iio: dps310: Add pressure sensing capability")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/dps310.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 45bdb8c7670f..35260b399390 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -50,9 +50,9 @@
 #define DPS310_CFG_REG		0x09
 #define  DPS310_INT_HL		BIT(7)
 #define  DPS310_TMP_SHIFT_EN	BIT(3)
-#define  DPS310_PRS_SHIFT_EN	BIT(4)
-#define  DPS310_FIFO_EN		BIT(5)
-#define  DPS310_SPI_EN		BIT(6)
+#define  DPS310_PRS_SHIFT_EN	BIT(2)
+#define  DPS310_FIFO_EN		BIT(1)
+#define  DPS310_SPI_EN		BIT(0)
 #define DPS310_RESET		0x0c
 #define  DPS310_RESET_MAGIC	0x09
 #define DPS310_COEF_BASE	0x10
-- 
2.43.0

[PATCH v8 02/10] iio: pressure: dps310: use a local device pointer in probe

[Rupesh Majhi]

probe() spells out &client->dev for every devm call. Take it into a local
instead. Keeps lines short as more calls are added later in this series.

No functional change.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/dps310.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 35260b399390..bd7da4f12749 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -845,11 +845,12 @@ static const struct iio_info dps310_info = {
 
 static int dps310_probe(struct i2c_client *client)
 {
+	struct device *dev = &client->dev;
 	struct dps310_data *data;
 	struct iio_dev *iio;
 	int rc;
 
-	iio = devm_iio_device_alloc(&client->dev,  sizeof(*data));
+	iio = devm_iio_device_alloc(dev, sizeof(*data));
 	if (!iio)
 		return -ENOMEM;
 
@@ -868,7 +869,7 @@ static int dps310_probe(struct i2c_client *client)
 		return PTR_ERR(data->regmap);
 
 	/* Register to run the device reset when the device is removed */
-	rc = devm_add_action_or_reset(&client->dev, dps310_reset, data);
+	rc = devm_add_action_or_reset(dev, dps310_reset, data);
 	if (rc)
 		return rc;
 
@@ -876,7 +877,7 @@ static int dps310_probe(struct i2c_client *client)
 	if (rc)
 		return rc;
 
-	rc = devm_iio_device_register(&client->dev, iio);
+	rc = devm_iio_device_register(dev, iio);
 	if (rc)
 		return rc;
 
-- 
2.43.0

[PATCH v8 03/10] iio: pressure: dps310: use get_unaligned_be24() for the 24-bit results

[Rupesh Majhi]

Pressure and temperature results are big-endian 24-bit values. Build them
with get_unaligned_be24() instead of open-coded shifts.

The coefficients are packed into the bytes rather than byte-aligned, so
they stay as they are.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/dps310.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index bd7da4f12749..e7f173e08e01 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -19,6 +19,7 @@
 #include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
+#include <linux/unaligned.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
@@ -468,7 +469,6 @@ static int dps310_read_pres_raw(struct dps310_data *data)
 	int rc;
 	int rate;
 	int timeout;
-	s32 raw;
 	u8 val[3];
 
 	if (mutex_lock_interruptible(&data->lock))
@@ -489,8 +489,7 @@ static int dps310_read_pres_raw(struct dps310_data *data)
 	if (rc < 0)
 		goto done;
 
-	raw = (val[0] << 16) | (val[1] << 8) | val[2];
-	data->pressure_raw = sign_extend32(raw, 23);
+	data->pressure_raw = sign_extend32(get_unaligned_be24(val), 23);
 
 done:
 	mutex_unlock(&data->lock);
@@ -502,14 +501,12 @@ static int dps310_read_temp_ready(struct dps310_data *data)
 {
 	int rc;
 	u8 val[3];
-	s32 raw;
 
 	rc = regmap_bulk_read(data->regmap, DPS310_TMP_BASE, val, sizeof(val));
 	if (rc < 0)
 		return rc;
 
-	raw = (val[0] << 16) | (val[1] << 8) | val[2];
-	data->temp_raw = sign_extend32(raw, 23);
+	data->temp_raw = sign_extend32(get_unaligned_be24(val), 23);
 
 	return 0;
 }
-- 
2.43.0

[PATCH v8 04/10] iio: pressure: dps310: take the lock once per raw read

[Rupesh Majhi]

A processed pressure read takes the lock twice: once in the raw read,
then again when dps310_calculate_pressure() trylocks to refresh the
temperature. The refresh is skipped whenever the lock is busy.

Split the raw reads into variants that expect the lock held and give each
channel a helper that takes it once for the whole sequence, so the
temperature refresh is unconditional. Buffered capture later in this
series needs the same shape.

Mark the functions that need the lock with __must_hold() rather than a
comment, and include cleanup.h, which ACQUIRE() needs and was coming in
transitively.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/dps310.c | 143 ++++++++++++++++++----------------
 1 file changed, 77 insertions(+), 66 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index e7f173e08e01..8cefca928077 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -14,6 +14,7 @@
  *  - Optionally support the FIFO
  */
 
+#include <linux/cleanup.h>
 #include <linux/i2c.h>
 #include <linux/limits.h>
 #include <linux/math64.h>
@@ -287,8 +288,8 @@ static int dps310_get_temp_precision(struct dps310_data *data, int *val)
 	return 0;
 }
 
-/* Called with lock held */
 static int dps310_set_pres_precision(struct dps310_data *data, int val)
+	__must_hold(&data->lock)
 {
 	int rc;
 	u8 shift_en;
@@ -306,8 +307,8 @@ static int dps310_set_pres_precision(struct dps310_data *data, int val)
 				  DPS310_PRS_PRC_BITS, ilog2(val));
 }
 
-/* Called with lock held */
 static int dps310_set_temp_precision(struct dps310_data *data, int val)
+	__must_hold(&data->lock)
 {
 	int rc;
 	u8 shift_en;
@@ -325,8 +326,8 @@ static int dps310_set_temp_precision(struct dps310_data *data, int val)
 				  DPS310_TMP_PRC_BITS, ilog2(val));
 }
 
-/* Called with lock held */
 static int dps310_set_pres_samp_freq(struct dps310_data *data, int freq)
+	__must_hold(&data->lock)
 {
 	u8 val;
 
@@ -339,8 +340,8 @@ static int dps310_set_pres_samp_freq(struct dps310_data *data, int freq)
 				  DPS310_PRS_RATE_BITS, val);
 }
 
-/* Called with lock held */
 static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
+	__must_hold(&data->lock)
 {
 	u8 val;
 
@@ -439,6 +440,7 @@ static int dps310_ready_status(struct dps310_data *data, int ready_bit, int time
 }
 
 static int dps310_ready(struct dps310_data *data, int ready_bit, int timeout)
+	__must_hold(&data->lock)
 {
 	int rc;
 
@@ -464,40 +466,36 @@ static int dps310_ready(struct dps310_data *data, int ready_bit, int timeout)
 	return 0;
 }
 
-static int dps310_read_pres_raw(struct dps310_data *data)
+static int dps310_read_pres_raw_locked(struct dps310_data *data)
+	__must_hold(&data->lock)
 {
 	int rc;
 	int rate;
 	int timeout;
 	u8 val[3];
 
-	if (mutex_lock_interruptible(&data->lock))
-		return -EINTR;
-
 	rc = dps310_get_pres_samp_freq(data, &rate);
 	if (rc)
-		goto done;
+		return rc;
 
 	timeout = DPS310_POLL_TIMEOUT_US(rate);
 
 	/* Poll for sensor readiness; base the timeout upon the sample rate. */
 	rc = dps310_ready(data, DPS310_PRS_RDY, timeout);
 	if (rc)
-		goto done;
+		return rc;
 
 	rc = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
 	if (rc < 0)
-		goto done;
+		return rc;
 
 	data->pressure_raw = sign_extend32(get_unaligned_be24(val), 23);
 
-done:
-	mutex_unlock(&data->lock);
-	return rc;
+	return 0;
 }
 
-/* Called with lock held */
 static int dps310_read_temp_ready(struct dps310_data *data)
+	__must_hold(&data->lock)
 {
 	int rc;
 	u8 val[3];
@@ -511,31 +509,40 @@ static int dps310_read_temp_ready(struct dps310_data *data)
 	return 0;
 }
 
-static int dps310_read_temp_raw(struct dps310_data *data)
+static int dps310_read_temp_raw_locked(struct dps310_data *data)
+	__must_hold(&data->lock)
 {
 	int rc;
 	int rate;
 	int timeout;
 
-	if (mutex_lock_interruptible(&data->lock))
-		return -EINTR;
-
 	rc = dps310_get_temp_samp_freq(data, &rate);
 	if (rc)
-		goto done;
+		return rc;
 
 	timeout = DPS310_POLL_TIMEOUT_US(rate);
 
 	/* Poll for sensor readiness; base the timeout upon the sample rate. */
 	rc = dps310_ready(data, DPS310_TMP_RDY, timeout);
 	if (rc)
-		goto done;
+		return rc;
+
+	return dps310_read_temp_ready(data);
+}
+
+/* Best effort: on error the previous temperature stands */
+static void dps310_refresh_temp_locked(struct dps310_data *data)
+	__must_hold(&data->lock)
+{
+	int rc;
+	int t_ready;
 
-	rc = dps310_read_temp_ready(data);
+	rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &t_ready);
+	if (rc)
+		return;
 
-done:
-	mutex_unlock(&data->lock);
-	return rc;
+	if (t_ready & DPS310_TMP_RDY)
+		dps310_read_temp_ready(data);
 }
 
 static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
@@ -577,59 +584,47 @@ static int dps310_write_raw(struct iio_dev *iio,
 			    struct iio_chan_spec const *chan, int val,
 			    int val2, long mask)
 {
-	int rc;
 	struct dps310_data *data = iio_priv(iio);
 
-	if (mutex_lock_interruptible(&data->lock))
+	ACQUIRE(mutex_intr, lock)(&data->lock);
+	if (ACQUIRE_ERR(mutex_intr, &lock))
 		return -EINTR;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		switch (chan->type) {
 		case IIO_PRESSURE:
-			rc = dps310_set_pres_samp_freq(data, val);
-			break;
+			return dps310_set_pres_samp_freq(data, val);
 
 		case IIO_TEMP:
-			rc = dps310_set_temp_samp_freq(data, val);
-			break;
+			return dps310_set_temp_samp_freq(data, val);
 
 		default:
-			rc = -EINVAL;
-			break;
+			return -EINVAL;
 		}
-		break;
 
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
 		switch (chan->type) {
 		case IIO_PRESSURE:
-			rc = dps310_set_pres_precision(data, val);
-			break;
+			return dps310_set_pres_precision(data, val);
 
 		case IIO_TEMP:
-			rc = dps310_set_temp_precision(data, val);
-			break;
+			return dps310_set_temp_precision(data, val);
 
 		default:
-			rc = -EINVAL;
-			break;
+			return -EINVAL;
 		}
-		break;
 
 	default:
-		rc = -EINVAL;
-		break;
+		return -EINVAL;
 	}
-
-	mutex_unlock(&data->lock);
-	return rc;
 }
 
 static int dps310_calculate_pressure(struct dps310_data *data, int *val)
+	__must_hold(&data->lock)
 {
 	int i;
 	int rc;
-	int t_ready;
 	int kpi;
 	int kti;
 	s64 rem = 0ULL;
@@ -653,15 +648,6 @@ static int dps310_calculate_pressure(struct dps310_data *data, int *val)
 	kp = (s64)kpi;
 	kt = (s64)kti;
 
-	/* Refresh temp if it's ready, otherwise just use the latest value */
-	if (mutex_trylock(&data->lock)) {
-		rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &t_ready);
-		if (rc >= 0 && t_ready & DPS310_TMP_RDY)
-			dps310_read_temp_ready(data);
-
-		mutex_unlock(&data->lock);
-	}
-
 	p = (s64)data->pressure_raw;
 	t = (s64)data->temp_raw;
 
@@ -707,6 +693,23 @@ static int dps310_calculate_pressure(struct dps310_data *data, int *val)
 	return 0;
 }
 
+static int dps310_read_pressure_value(struct dps310_data *data, int *val)
+{
+	int rc;
+
+	ACQUIRE(mutex_intr, lock)(&data->lock);
+	if (ACQUIRE_ERR(mutex_intr, &lock))
+		return -EINTR;
+
+	rc = dps310_read_pres_raw_locked(data);
+	if (rc)
+		return rc;
+
+	dps310_refresh_temp_locked(data);
+
+	return dps310_calculate_pressure(data, val);
+}
+
 static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
 				long mask)
 {
@@ -721,11 +724,7 @@ static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_PROCESSED:
-		rc = dps310_read_pres_raw(data);
-		if (rc)
-			return rc;
-
-		rc = dps310_calculate_pressure(data, val);
+		rc = dps310_read_pressure_value(data, val);
 		if (rc)
 			return rc;
 
@@ -744,6 +743,7 @@ static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
 }
 
 static int dps310_calculate_temp(struct dps310_data *data, int *val)
+	__must_hold(&data->lock)
 {
 	s64 c0;
 	s64 t;
@@ -765,6 +765,21 @@ static int dps310_calculate_temp(struct dps310_data *data, int *val)
 	return 0;
 }
 
+static int dps310_read_temp_value(struct dps310_data *data, int *val)
+{
+	int rc;
+
+	ACQUIRE(mutex_intr, lock)(&data->lock);
+	if (ACQUIRE_ERR(mutex_intr, &lock))
+		return -EINTR;
+
+	rc = dps310_read_temp_raw_locked(data);
+	if (rc)
+		return rc;
+
+	return dps310_calculate_temp(data, val);
+}
+
 static int dps310_read_temp(struct dps310_data *data, int *val, int *val2,
 			    long mask)
 {
@@ -779,11 +794,7 @@ static int dps310_read_temp(struct dps310_data *data, int *val, int *val2,
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_PROCESSED:
-		rc = dps310_read_temp_raw(data);
-		if (rc)
-			return rc;
-
-		rc = dps310_calculate_temp(data, val);
+		rc = dps310_read_temp_value(data, val);
 		if (rc)
 			return rc;
 
-- 
2.43.0

[PATCH v8 05/10] iio: pressure: dps310: add triggered buffer support

[Rupesh Majhi]

Add a triggered buffer to capture continuously on both channels instead
of one sysfs read at a time.

Raw register value is not useful on its own, pressure has to go through
the compensation polynomial and needs a temperature reading. Report raw
in Pa with 1/1000 scale to keep full resolution in the buffer without
changing what the existing processed attribute reports.

Raw and processed reads return -EBUSY while buffer is on, so does any
reconfiguration.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/Kconfig  |   2 +
 drivers/iio/pressure/dps310.c | 152 ++++++++++++++++++++++++++++++++--
 2 files changed, 149 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index 838a8340c4c0..cef8b90b9ae7 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -112,6 +112,8 @@ config DPS310
 	tristate "Infineon DPS310 pressure and temperature sensor"
 	depends on I2C
 	select REGMAP_I2C
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Support for the Infineon DPS310 digital barometric pressure sensor.
 	  It can be accessed over I2C bus.
diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 8cefca928077..85df58ac1809 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -22,8 +22,11 @@
 #include <linux/regmap.h>
 #include <linux/unaligned.h>
 
+#include <linux/iio/buffer.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
 
 #define DPS310_DEV_NAME		"dps310"
 
@@ -94,19 +97,51 @@ struct dps310_data {
 	bool timeout_recovery_failed;
 };
 
+enum dps310_scan_index {
+	DPS310_SCAN_TEMP,
+	DPS310_SCAN_PRESSURE,
+	DPS310_SCAN_TIMESTAMP,
+};
+
 static const struct iio_chan_spec dps310_channels[] = {
 	{
 		.type = IIO_TEMP,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
 			BIT(IIO_CHAN_INFO_SAMP_FREQ) |
 			BIT(IIO_CHAN_INFO_PROCESSED),
+		.scan_index = DPS310_SCAN_TEMP,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
 	},
 	{
 		.type = IIO_PRESSURE,
+		/*
+		 * _raw here is already compensated (section 4.9.1, which needs
+		 * a temperature too) and in Pa; _scale converts to the kPa the
+		 * ABI wants. _processed predates buffers and has to stay.
+		 *
+		 * Do not copy this into other drivers. A _raw that is not the
+		 * raw register value is only tolerable because the alternative
+		 * is losing resolution or breaking existing _processed users.
+		 */
 		.info_mask_separate = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
 			BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+			BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE) |
 			BIT(IIO_CHAN_INFO_PROCESSED),
+		.scan_index = DPS310_SCAN_PRESSURE,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
 	},
+	IIO_CHAN_SOFT_TIMESTAMP(DPS310_SCAN_TIMESTAMP),
 };
 
 /* To be called after checking the COEF_RDY bit in MEAS_CFG */
@@ -586,6 +621,11 @@ static int dps310_write_raw(struct iio_dev *iio,
 {
 	struct dps310_data *data = iio_priv(iio);
 
+	/* Reconfiguring mid-capture would change the values being captured */
+	IIO_DEV_ACQUIRE_DIRECT_MODE(iio, claim);
+	if (IIO_DEV_ACQUIRE_FAILED(claim))
+		return -EBUSY;
+
 	ACQUIRE(mutex_intr, lock)(&data->lock);
 	if (ACQUIRE_ERR(mutex_intr, &lock))
 		return -EINTR;
@@ -723,6 +763,13 @@ static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
 
 		return IIO_VAL_INT;
 
+	case IIO_CHAN_INFO_RAW:
+		rc = dps310_read_pressure_value(data, val);
+		if (rc)
+			return rc;
+
+		return IIO_VAL_INT;
+
 	case IIO_CHAN_INFO_PROCESSED:
 		rc = dps310_read_pressure_value(data, val);
 		if (rc)
@@ -731,6 +778,12 @@ static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
 		*val2 = 1000; /* Convert Pa to KPa per IIO ABI */
 		return IIO_VAL_FRACTIONAL;
 
+	case IIO_CHAN_INFO_SCALE:
+		/* The raw value is in Pa, the ABI wants kPa */
+		*val = 1;
+		*val2 = 1000;
+		return IIO_VAL_FRACTIONAL;
+
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
 		rc = dps310_get_pres_precision(data, val);
 		if (rc)
@@ -812,12 +865,10 @@ static int dps310_read_temp(struct dps310_data *data, int *val, int *val2,
 	}
 }
 
-static int dps310_read_raw(struct iio_dev *iio,
-			   struct iio_chan_spec const *chan,
-			   int *val, int *val2, long mask)
+static int dps310_read_channel(struct dps310_data *data,
+			       struct iio_chan_spec const *chan,
+			       int *val, int *val2, long mask)
 {
-	struct dps310_data *data = iio_priv(iio);
-
 	switch (chan->type) {
 	case IIO_PRESSURE:
 		return dps310_read_pressure(data, val, val2, mask);
@@ -830,6 +881,87 @@ static int dps310_read_raw(struct iio_dev *iio,
 	}
 }
 
+static int dps310_read_raw(struct iio_dev *iio,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct dps310_data *data = iio_priv(iio);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+	case IIO_CHAN_INFO_PROCESSED: {
+		/* This consumes the measurement the capture path reads */
+		IIO_DEV_ACQUIRE_DIRECT_MODE(iio, claim);
+		if (IIO_DEV_ACQUIRE_FAILED(claim))
+			return -EBUSY;
+
+		return dps310_read_channel(data, chan, val, val2, mask);
+	}
+	default:
+		return dps310_read_channel(data, chan, val, val2, mask);
+	}
+}
+
+static int dps310_fill_channels(struct dps310_data *data,
+				const unsigned long *scan_mask,
+				s32 channels[2])
+	__must_hold(&data->lock)
+{
+	unsigned int i;
+	int rc;
+
+	/* Compensation needs a temperature, so it is sampled either way */
+	rc = dps310_read_temp_raw_locked(data);
+	if (rc)
+		return rc;
+
+	i = 0;
+	if (test_bit(DPS310_SCAN_TEMP, scan_mask)) {
+		/* Millidegrees Celsius */
+		rc = dps310_calculate_temp(data, &channels[i++]);
+		if (rc)
+			return rc;
+	}
+
+	if (test_bit(DPS310_SCAN_PRESSURE, scan_mask)) {
+		rc = dps310_read_pres_raw_locked(data);
+		if (rc)
+			return rc;
+
+		/* Pascals, see the channel definition */
+		rc = dps310_calculate_pressure(data, &channels[i++]);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+static irqreturn_t dps310_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *iio = pf->indio_dev;
+	struct dps310_data *data = iio_priv(iio);
+	struct {
+		s32 channels[2];
+		aligned_s64 timestamp;
+	} scan = { };
+	int rc;
+
+	mutex_lock(&data->lock);
+	rc = dps310_fill_channels(data, iio->active_scan_mask, scan.channels);
+	mutex_unlock(&data->lock);
+	if (rc)
+		goto err;
+
+	iio_push_to_buffers_with_ts(iio, &scan, sizeof(scan), iio_get_time_ns(iio));
+
+err:
+	iio_trigger_notify_done(iio->trig);
+
+	return IRQ_HANDLED;
+}
+
 static void dps310_reset(void *action_data)
 {
 	struct dps310_data *data = action_data;
@@ -885,6 +1017,16 @@ static int dps310_probe(struct i2c_client *client)
 	if (rc)
 		return rc;
 
+	/*
+	 * The device measures continuously in background mode, so a capture is
+	 * just a read of the latest results. The trigger is not aligned with
+	 * the measurements, so the timestamp is taken in the handler.
+	 */
+	rc = devm_iio_triggered_buffer_setup(dev, iio, NULL,
+					     dps310_trigger_handler, NULL);
+	if (rc)
+		return rc;
+
 	rc = devm_iio_device_register(dev, iio);
 	if (rc)
 		return rc;
-- 
2.43.0

[PATCH v8 06/10] iio: core: add an accessor for scan_timestamp

[Rupesh Majhi]

indio_dev->scan_timestamp is __private, so a driver has no way to ask
whether the timestamp channel is in the current scan. Hide the
ACCESS_PRIVATE() behind a read-only helper, the way iio_get_masklength()
already does.

The dps310 FIFO patch later in this series is the first user: that
hardware does not timestamp entries, so it refuses a buffer with the
timestamp channel enabled.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 include/linux/iio/iio.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 989c1db8fb36..a893e36be988 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -1083,6 +1083,15 @@ static inline unsigned int iio_get_masklength(const struct iio_dev *indio_dev)
 	return ACCESS_PRIVATE(indio_dev, masklength);
 }
 
+/**
+ * iio_scan_timestamp_enabled - Is the timestamp channel in the current scan
+ * @indio_dev: the IIO device to check
+ */
+static inline bool iio_scan_timestamp_enabled(const struct iio_dev *indio_dev)
+{
+	return ACCESS_PRIVATE(indio_dev, scan_timestamp);
+}
+
 int iio_active_scan_mask_index(struct iio_dev *indio_dev);
 
 /**
-- 
2.43.0

[PATCH v8 07/10] iio: pressure: dps310: read buffered samples from the hardware FIFO

[Rupesh Majhi]

The DPS310 has a 32-entry FIFO shared by both measurements. Drain it from
a work item and push what it held, so a buffered capture needs no
trigger. Nothing in tree wires the interrupt pin, so the work rearms
itself at half the time the FIFO takes to fill.

Entries carry one measurement each, so a pressure entry is compensated
with the temperature ahead of it. Pressure read before the first
temperature of a session is held until one arrives rather than dropped,
so the first push can wait a temperature period.

FIFO entries are not timestamped, so postenable refuses the timestamp
channel unless a trigger is attached.

Tested on a DPS310 on a BeagleBone Black.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/dps310.c | 364 +++++++++++++++++++++++++++++++++-
 1 file changed, 354 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 85df58ac1809..ba59413d8e11 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -2,16 +2,11 @@
 // Copyright IBM Corp 2019
 /*
  * The DPS310 is a barometric pressure and temperature sensor.
- * Currently only reading a single temperature is supported by
- * this driver.
  *
  * https://www.infineon.com/dgdl/?fileId=5546d462576f34750157750826c42242
  *
  * Temperature calculation:
  *   c0 * 0.5 + c1 * T_raw / kT °C
- *
- * TODO:
- *  - Optionally support the FIFO
  */
 
 #include <linux/cleanup.h>
@@ -20,7 +15,10 @@
 #include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
+#include <linux/slab.h>
 #include <linux/unaligned.h>
+#include <linux/units.h>
+#include <linux/workqueue.h>
 
 #include <linux/iio/buffer.h>
 #include <linux/iio/iio.h>
@@ -59,9 +57,22 @@
 #define  DPS310_FIFO_EN		BIT(1)
 #define  DPS310_SPI_EN		BIT(0)
 #define DPS310_RESET		0x0c
+#define  DPS310_FIFO_FLUSH	BIT(7)
 #define  DPS310_RESET_MAGIC	0x09
 #define DPS310_COEF_BASE	0x10
 
+/* Section 4.8: 32 shared entries. Stops when full, so late drains lose data */
+#define DPS310_FIFO_DEPTH	32
+
+/* Read back once the FIFO is empty */
+#define DPS310_FIFO_EMPTY_VAL	0x800000
+
+/* LSB tags which measurement produced the entry */
+#define DPS310_FIFO_TAG_PRS	BIT(0)
+
+#define DPS310_DRAIN_MIN_MS	20
+#define DPS310_DRAIN_MAX_MS	(2 * MSEC_PER_SEC)
+
 /* Make sure sleep time is <= 30ms for usleep_range */
 #define DPS310_POLL_SLEEP_US(t)		min(30000, (t) / 8)
 /* Silently handle error in rate value here */
@@ -95,6 +106,22 @@ struct dps310_data {
 	s32 pressure_raw;
 	s32 temp_raw;
 	bool timeout_recovery_failed;
+	bool fifo_temp_valid;
+
+	/* Used only while the FIFO is enabled */
+	struct iio_dev *iio;
+	struct delayed_work fifo_work;
+	s32 *fifo_hold;
+	unsigned int fifo_hold_max;
+	unsigned int fifo_held;
+	unsigned int drain_interval_ms;
+	s32 fifo_temp_raw;
+};
+
+enum dps310_fifo_entry {
+	DPS310_FIFO_EMPTY,
+	DPS310_FIFO_TEMP,
+	DPS310_FIFO_PRESSURE,
 };
 
 enum dps310_scan_index {
@@ -937,6 +964,302 @@ static int dps310_fill_channels(struct dps310_data *data,
 	return 0;
 }
 
+static int dps310_fifo_hw_flush(struct dps310_data *data)
+	__must_hold(&data->lock)
+{
+	return regmap_write(data->regmap, DPS310_RESET, DPS310_FIFO_FLUSH);
+}
+
+static int dps310_fifo_set_enable(struct dps310_data *data, bool enable)
+	__must_hold(&data->lock)
+{
+	return regmap_assign_bits(data->regmap, DPS310_CFG_REG, DPS310_FIFO_EN,
+				  enable);
+}
+
+/*
+ * No interrupt pin is wired in tree, so drain on a timer. Both measurements
+ * share the entries, so they fill it together.
+ */
+static unsigned int dps310_fifo_interval(int prs_rate, int tmp_rate)
+{
+	unsigned int fill_ms;
+
+	fill_ms = MSEC_PER_SEC * DPS310_FIFO_DEPTH / (prs_rate + tmp_rate);
+
+	return clamp(fill_ms / 2, DPS310_DRAIN_MIN_MS, DPS310_DRAIN_MAX_MS);
+}
+
+/* Returns which measurement the entry came from, or a negative error */
+static int dps310_fifo_read_entry(struct dps310_data *data, s32 *value)
+	__must_hold(&data->lock)
+{
+	u8 val[3];
+	s32 raw;
+	int rc;
+
+	/* Entries come out of the pressure registers whichever made them */
+	rc = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
+	if (rc < 0)
+		return rc;
+
+	raw = get_unaligned_be24(val);
+	if (raw == DPS310_FIFO_EMPTY_VAL)
+		return DPS310_FIFO_EMPTY;
+
+	*value = sign_extend32(raw, 23);
+
+	return raw & DPS310_FIFO_TAG_PRS ? DPS310_FIFO_PRESSURE :
+					   DPS310_FIFO_TEMP;
+}
+
+static int dps310_fifo_push_scan(struct dps310_data *data, s32 temp_raw,
+				 s32 pressure_raw)
+	__must_hold(&data->lock)
+{
+	struct iio_dev *iio = data->iio;
+	s32 channels[2] = { };
+	unsigned int i;
+	int rc;
+
+	/* Direct-mode claim keeps sysfs reads off these */
+	data->temp_raw = temp_raw;
+	data->pressure_raw = pressure_raw;
+
+	i = 0;
+	if (test_bit(DPS310_SCAN_TEMP, iio->active_scan_mask)) {
+		rc = dps310_calculate_temp(data, &channels[i++]);
+		if (rc)
+			return rc;
+	}
+
+	if (test_bit(DPS310_SCAN_PRESSURE, iio->active_scan_mask)) {
+		rc = dps310_calculate_pressure(data, &channels[i++]);
+		if (rc)
+			return rc;
+	}
+
+	iio_push_to_buffers(iio, channels);
+
+	return 0;
+}
+
+/* Pressure seen before any temperature, kept until one turns up */
+static void dps310_fifo_hold(struct dps310_data *data, s32 pressure_raw)
+	__must_hold(&data->lock)
+{
+	if (data->fifo_held < data->fifo_hold_max)
+		data->fifo_hold[data->fifo_held++] = pressure_raw;
+}
+
+/* Returns scans pushed */
+static int dps310_fifo_push_held(struct dps310_data *data)
+	__must_hold(&data->lock)
+{
+	unsigned int held = data->fifo_held;
+	unsigned int i;
+	int rc = 0;
+
+	for (i = 0; i < held; i++) {
+		rc = dps310_fifo_push_scan(data, data->fifo_temp_raw,
+					   data->fifo_hold[i]);
+		if (rc)
+			break;
+	}
+
+	/* What did not go out stays for the next drain */
+	data->fifo_held = held - i;
+	memmove(data->fifo_hold, &data->fifo_hold[i],
+		data->fifo_held * sizeof(*data->fifo_hold));
+
+	return rc ? rc : i;
+}
+
+/*
+ * Read the batch out before compensating it, so a pressure entry pairs with
+ * the temperature preceding it rather than the last one in the batch.
+ *
+ * Returns scans pushed.
+ */
+static int dps310_fifo_drain(struct dps310_data *data)
+	__must_hold(&data->lock)
+{
+	bool pressure_enabled = test_bit(DPS310_SCAN_PRESSURE,
+					 data->iio->active_scan_mask);
+	u8 kind[DPS310_FIFO_DEPTH];
+	s32 raw[DPS310_FIFO_DEPTH];
+	unsigned int pushed = 0;
+	unsigned int cnt, i;
+	int rc;
+
+	for (cnt = 0; cnt < DPS310_FIFO_DEPTH; cnt++) {
+		rc = dps310_fifo_read_entry(data, &raw[cnt]);
+		if (rc < 0)
+			return rc;
+
+		if (rc == DPS310_FIFO_EMPTY)
+			break;
+
+		kind[cnt] = rc;
+	}
+
+	for (i = 0; i < cnt; i++) {
+		if (kind[i] == DPS310_FIFO_TEMP) {
+			data->fifo_temp_raw = raw[i];
+			data->fifo_temp_valid = true;
+
+			if (!pressure_enabled) {
+				rc = dps310_fifo_push_scan(data, raw[i], 0);
+				if (rc)
+					return rc;
+
+				pushed++;
+				continue;
+			}
+
+			rc = dps310_fifo_push_held(data);
+			if (rc < 0)
+				return rc;
+
+			pushed += rc;
+			continue;
+		}
+
+		if (!pressure_enabled)
+			continue;
+
+		if (!data->fifo_temp_valid) {
+			dps310_fifo_hold(data, raw[i]);
+			continue;
+		}
+
+		rc = dps310_fifo_push_scan(data, data->fifo_temp_raw, raw[i]);
+		if (rc)
+			return rc;
+
+		pushed++;
+	}
+
+	return pushed;
+}
+
+static void dps310_fifo_work(struct work_struct *work)
+{
+	struct dps310_data *data = container_of(to_delayed_work(work),
+						struct dps310_data, fifo_work);
+	int rc;
+
+	mutex_lock(&data->lock);
+	rc = dps310_fifo_drain(data);
+	mutex_unlock(&data->lock);
+
+	if (rc < 0)
+		dev_dbg(&data->client->dev, "FIFO drain failed: %d\n", rc);
+
+	schedule_delayed_work(&data->fifo_work,
+			      msecs_to_jiffies(data->drain_interval_ms));
+}
+
+/*
+ * First temperature is one temperature period away at most, which bounds the
+ * pressure before it. Rates cannot change while the buffer runs.
+ */
+static int dps310_fifo_hold_alloc(struct dps310_data *data, int prs_rate,
+				  int tmp_rate)
+	__must_hold(&data->lock)
+{
+	data->fifo_temp_valid = false;
+	data->fifo_held = 0;
+	data->fifo_hold = NULL;
+	data->fifo_hold_max = 0;
+
+	if (!test_bit(DPS310_SCAN_PRESSURE, data->iio->active_scan_mask))
+		return 0;
+
+	data->fifo_hold_max = prs_rate / tmp_rate + 2;
+	data->fifo_hold = kcalloc(data->fifo_hold_max, sizeof(*data->fifo_hold),
+				  GFP_KERNEL);
+	if (!data->fifo_hold)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int dps310_buffer_postenable(struct iio_dev *iio)
+{
+	struct dps310_data *data = iio_priv(iio);
+	int rc, prs_rate, tmp_rate;
+
+	/* An attached trigger drives the capture instead, FIFO stays off */
+	if (iio_device_get_current_mode(iio) == INDIO_BUFFER_TRIGGERED)
+		return 0;
+
+	/* Entries are not timestamped and the drain timer is no substitute */
+	if (iio_scan_timestamp_enabled(iio))
+		return -EINVAL;
+
+	guard(mutex)(&data->lock);
+
+	rc = dps310_get_pres_samp_freq(data, &prs_rate);
+	if (rc)
+		return rc;
+
+	rc = dps310_get_temp_samp_freq(data, &tmp_rate);
+	if (rc)
+		return rc;
+
+	data->drain_interval_ms = dps310_fifo_interval(prs_rate, tmp_rate);
+
+	rc = dps310_fifo_hold_alloc(data, prs_rate, tmp_rate);
+	if (rc)
+		return rc;
+
+	/* Drop whatever accumulated before enable */
+	rc = dps310_fifo_hw_flush(data);
+	if (rc)
+		goto err_hold;
+
+	rc = dps310_fifo_set_enable(data, true);
+	if (rc)
+		goto err_hold;
+
+	schedule_delayed_work(&data->fifo_work,
+			      msecs_to_jiffies(data->drain_interval_ms));
+
+	return 0;
+
+err_hold:
+	kfree(data->fifo_hold);
+
+	return rc;
+}
+
+static int dps310_buffer_predisable(struct iio_dev *iio)
+{
+	struct dps310_data *data = iio_priv(iio);
+	int rc;
+
+	if (iio_device_get_current_mode(iio) == INDIO_BUFFER_TRIGGERED)
+		return 0;
+
+	cancel_delayed_work_sync(&data->fifo_work);
+
+	guard(mutex)(&data->lock);
+
+	kfree(data->fifo_hold);
+
+	rc = dps310_fifo_set_enable(data, false);
+	if (rc)
+		return rc;
+
+	return dps310_fifo_hw_flush(data);
+}
+
+static const struct iio_buffer_setup_ops dps310_buffer_setup_ops = {
+	.postenable = dps310_buffer_postenable,
+	.predisable = dps310_buffer_predisable,
+};
+
 static irqreturn_t dps310_trigger_handler(int irq, void *p)
 {
 	struct iio_poll_func *pf = p;
@@ -969,6 +1292,14 @@ static void dps310_reset(void *action_data)
 	dps310_reset_wait(data);
 }
 
+/* The drain rearms itself, so stop it even if the buffer never disabled */
+static void dps310_cancel_fifo_work(void *action_data)
+{
+	struct dps310_data *data = action_data;
+
+	cancel_delayed_work_sync(&data->fifo_work);
+}
+
 static const struct regmap_config dps310_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
@@ -996,13 +1327,20 @@ static int dps310_probe(struct i2c_client *client)
 
 	data = iio_priv(iio);
 	data->client = client;
+	data->iio = iio;
 	mutex_init(&data->lock);
+	INIT_DELAYED_WORK(&data->fifo_work, dps310_fifo_work);
 
 	iio->name = DPS310_DEV_NAME;
 	iio->channels = dps310_channels;
 	iio->num_channels = ARRAY_SIZE(dps310_channels);
 	iio->info = &dps310_info;
-	iio->modes = INDIO_DIRECT_MODE;
+	/*
+	 * Both modes advertised: the core picks TRIGGERED with a trigger
+	 * attached and falls back to SOFTWARE, which the FIFO path uses.
+	 */
+	iio->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_TRIGGERED |
+		     INDIO_BUFFER_SOFTWARE;
 
 	data->regmap = devm_regmap_init_i2c(client, &dps310_regmap_config);
 	if (IS_ERR(data->regmap))
@@ -1018,12 +1356,18 @@ static int dps310_probe(struct i2c_client *client)
 		return rc;
 
 	/*
-	 * The device measures continuously in background mode, so a capture is
-	 * just a read of the latest results. The trigger is not aligned with
-	 * the measurements, so the timestamp is taken in the handler.
+	 * The device measures continuously in background mode, so a triggered
+	 * capture is just a read of the latest results. The setup ops run the
+	 * FIFO drain when no trigger is attached. The trigger is not aligned
+	 * with the measurements, so the timestamp is taken in the handler.
 	 */
 	rc = devm_iio_triggered_buffer_setup(dev, iio, NULL,
-					     dps310_trigger_handler, NULL);
+					     dps310_trigger_handler,
+					     &dps310_buffer_setup_ops);
+	if (rc)
+		return rc;
+
+	rc = devm_add_action_or_reset(dev, dps310_cancel_fifo_work, data);
 	if (rc)
 		return rc;
 
-- 
2.43.0

[PATCH v8 08/10] iio: pressure: dps310: derive the drain interval from the watermark

[Rupesh Majhi]

The drain interval only tracked how fast the FIFO fills, so a small
watermark still waited half a FIFO for its samples. Take the watermark
as the number of scans to wait for, but never drain slower than half a
fill.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/dps310.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index ba59413d8e11..974630eca547 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -114,6 +114,7 @@ struct dps310_data {
 	s32 *fifo_hold;
 	unsigned int fifo_hold_max;
 	unsigned int fifo_held;
+	unsigned int watermark;
 	unsigned int drain_interval_ms;
 	s32 fifo_temp_raw;
 };
@@ -981,13 +982,28 @@ static int dps310_fifo_set_enable(struct dps310_data *data, bool enable)
  * No interrupt pin is wired in tree, so drain on a timer. Both measurements
  * share the entries, so they fill it together.
  */
-static unsigned int dps310_fifo_interval(int prs_rate, int tmp_rate)
+static unsigned int dps310_fifo_interval(struct dps310_data *data, int prs_rate,
+					 int tmp_rate)
 {
-	unsigned int fill_ms;
+	unsigned int fill_ms, want_ms;
+	int scan_rate;
 
 	fill_ms = MSEC_PER_SEC * DPS310_FIFO_DEPTH / (prs_rate + tmp_rate);
 
-	return clamp(fill_ms / 2, DPS310_DRAIN_MIN_MS, DPS310_DRAIN_MAX_MS);
+	/*
+	 * There is no hardware watermark, so take it as the number of scans
+	 * the user will wait for and drain at that rate. Scans come from
+	 * whichever measurement drives them.
+	 */
+	if (test_bit(DPS310_SCAN_PRESSURE, data->iio->active_scan_mask))
+		scan_rate = prs_rate;
+	else
+		scan_rate = tmp_rate;
+
+	want_ms = data->watermark * MSEC_PER_SEC / scan_rate;
+
+	return clamp(min(want_ms, fill_ms / 2), DPS310_DRAIN_MIN_MS,
+		     DPS310_DRAIN_MAX_MS);
 }
 
 /* Returns which measurement the entry came from, or a negative error */
@@ -1185,6 +1201,15 @@ static int dps310_fifo_hold_alloc(struct dps310_data *data, int prs_rate,
 	return 0;
 }
 
+static int dps310_hwfifo_set_watermark(struct iio_dev *iio, unsigned int val)
+{
+	struct dps310_data *data = iio_priv(iio);
+
+	data->watermark = clamp(val, 1, DPS310_FIFO_DEPTH);
+
+	return 0;
+}
+
 static int dps310_buffer_postenable(struct iio_dev *iio)
 {
 	struct dps310_data *data = iio_priv(iio);
@@ -1208,7 +1233,7 @@ static int dps310_buffer_postenable(struct iio_dev *iio)
 	if (rc)
 		return rc;
 
-	data->drain_interval_ms = dps310_fifo_interval(prs_rate, tmp_rate);
+	data->drain_interval_ms = dps310_fifo_interval(data, prs_rate, tmp_rate);
 
 	rc = dps310_fifo_hold_alloc(data, prs_rate, tmp_rate);
 	if (rc)
@@ -1312,6 +1337,7 @@ static const struct regmap_config dps310_regmap_config = {
 static const struct iio_info dps310_info = {
 	.read_raw = dps310_read_raw,
 	.write_raw = dps310_write_raw,
+	.hwfifo_set_watermark = dps310_hwfifo_set_watermark,
 };
 
 static int dps310_probe(struct i2c_client *client)
@@ -1328,6 +1354,7 @@ static int dps310_probe(struct i2c_client *client)
 	data = iio_priv(iio);
 	data->client = client;
 	data->iio = iio;
+	data->watermark = 1;
 	mutex_init(&data->lock);
 	INIT_DELAYED_WORK(&data->fifo_work, dps310_fifo_work);
 
-- 
2.43.0

[PATCH v8 09/10] iio: pressure: dps310: implement .hwfifo_flush_to_buffer()

[Rupesh Majhi]

Let userspace drain the FIFO on demand rather than only from the
periodic drain.

With a trigger attached the FIFO is not running, so there is nothing to
flush and the hook returns 0.

Hold the mode across the drain, so a concurrent buffer disable cannot
free active_scan_mask while it runs.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/dps310.c | 36 ++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 974630eca547..59203df1ae35 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -1093,22 +1093,30 @@ static int dps310_fifo_push_held(struct dps310_data *data)
 
 /*
  * Read the batch out before compensating it, so a pressure entry pairs with
- * the temperature preceding it rather than the last one in the batch.
+ * the temperature preceding it rather than the last one in the batch. Stop
+ * reading at max_scans rather than after it, since entries leave the hardware
+ * as they are read and any extra would have to be thrown away. max_scans of
+ * zero drains everything.
  *
  * Returns scans pushed.
  */
-static int dps310_fifo_drain(struct dps310_data *data)
+static int dps310_fifo_drain(struct dps310_data *data, unsigned int max_scans)
 	__must_hold(&data->lock)
 {
 	bool pressure_enabled = test_bit(DPS310_SCAN_PRESSURE,
 					 data->iio->active_scan_mask);
 	u8 kind[DPS310_FIFO_DEPTH];
 	s32 raw[DPS310_FIFO_DEPTH];
+	unsigned int scans = 0;
 	unsigned int pushed = 0;
 	unsigned int cnt, i;
+	bool is_pressure;
 	int rc;
 
 	for (cnt = 0; cnt < DPS310_FIFO_DEPTH; cnt++) {
+		if (max_scans && scans >= max_scans)
+			break;
+
 		rc = dps310_fifo_read_entry(data, &raw[cnt]);
 		if (rc < 0)
 			return rc;
@@ -1116,7 +1124,12 @@ static int dps310_fifo_drain(struct dps310_data *data)
 		if (rc == DPS310_FIFO_EMPTY)
 			break;
 
+		is_pressure = rc == DPS310_FIFO_PRESSURE;
 		kind[cnt] = rc;
+
+		/* Only the measurement that drives the scans counts */
+		if (is_pressure == pressure_enabled)
+			scans++;
 	}
 
 	for (i = 0; i < cnt; i++) {
@@ -1166,7 +1179,7 @@ static void dps310_fifo_work(struct work_struct *work)
 	int rc;
 
 	mutex_lock(&data->lock);
-	rc = dps310_fifo_drain(data);
+	rc = dps310_fifo_drain(data, 0);
 	mutex_unlock(&data->lock);
 
 	if (rc < 0)
@@ -1201,6 +1214,22 @@ static int dps310_fifo_hold_alloc(struct dps310_data *data, int prs_rate,
 	return 0;
 }
 
+static int dps310_hwfifo_flush(struct iio_dev *iio, unsigned int count)
+{
+	struct dps310_data *data = iio_priv(iio);
+
+	/* Holding the mode keeps active_scan_mask alive across the drain */
+	IIO_DEV_GUARD_CURRENT_MODE(iio);
+
+	/* A trigger drives the capture instead and leaves the FIFO empty */
+	if (iio_device_get_current_mode(iio) != INDIO_BUFFER_SOFTWARE)
+		return 0;
+
+	guard(mutex)(&data->lock);
+
+	return dps310_fifo_drain(data, count);
+}
+
 static int dps310_hwfifo_set_watermark(struct iio_dev *iio, unsigned int val)
 {
 	struct dps310_data *data = iio_priv(iio);
@@ -1338,6 +1367,7 @@ static const struct iio_info dps310_info = {
 	.read_raw = dps310_read_raw,
 	.write_raw = dps310_write_raw,
 	.hwfifo_set_watermark = dps310_hwfifo_set_watermark,
+	.hwfifo_flush_to_buffer = dps310_hwfifo_flush,
 };
 
 static int dps310_probe(struct i2c_client *client)
-- 
2.43.0

[PATCH v8 10/10] iio: pressure: dps310: check the lock markings with context analysis

[Rupesh Majhi]

__must_hold() markings added earlier in this series are only
documentation unless the file opts in, so switch the analysis on for
dps310.o.

Clean with clang 23.1.0 and CONFIG_WARN_CONTEXT_ANALYSIS=y. It does run:
dropping the lock around dps310_fifo_drain() warns rather than going
quietly.

Assisted-by: LLM
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
 drivers/iio/pressure/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
index bc0d11a20acc..4b1a05f7a0bd 100644
--- a/drivers/iio/pressure/Makefile
+++ b/drivers/iio/pressure/Makefile
@@ -3,6 +3,8 @@
 # Makefile for industrial I/O pressure drivers
 #
 
+CONTEXT_ANALYSIS_dps310.o := y
+
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_ABP060MG) += abp060mg.o
 obj-$(CONFIG_ABP2030PA) += abp2030pa.o
-- 
2.43.0