[PATCH v7 04/10] iio: pressure: dps310: take the lock once per raw read

[Rupesh Majhi <zoone.rupert@gmail.com>]

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