[PATCH v2] iio: pressure: dps310: don't wait for new temperature in trigger handler

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

Each scan waits for a new temperature result before reading pressure.
With pressure sampled faster than temperature, scans then come at the
temperature rate: an 8 Hz trigger with temperature at its default 1 Hz
gives one scan a second.

Read pressure first and take the latest temperature, as a direct
pressure read already does. Wait for temperature only when pressure is
not in the scan. Read a temperature in probe, so there is a latest one
from the first scan on.

Fixes: 9b7cad9ce2ed ("iio: pressure: dps310: add triggered buffer support")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20261110154254.39092-1-zoone.rupert%40gmail.com
Signed-off-by: Rupesh Majhi <zoone.rupert@gmail.com>
---
v2: read a temperature in probe, so the first scans have one (Arnav Kapoor)
v1: https://lore.kernel.org/linux-iio/20261111195118.36853-1-zoone.rupert@gmail.com/

Cc: Arnav Kapoor <kapoorarnav43@gmail.com>
Cc: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

 drivers/iio/pressure/dps310.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 85df58ac1809..3d05540f95dd 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -910,10 +910,18 @@ static int dps310_fill_channels(struct dps310_data *data,
 	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;
+	if (test_bit(DPS310_SCAN_PRESSURE, scan_mask)) {
+		rc = dps310_read_pres_raw_locked(data);
+		if (rc)
+			return rc;
+
+		/* Waiting here would hold scans to the temperature rate */
+		dps310_refresh_temp_locked(data);
+	} else {
+		rc = dps310_read_temp_raw_locked(data);
+		if (rc)
+			return rc;
+	}
 
 	i = 0;
 	if (test_bit(DPS310_SCAN_TEMP, scan_mask)) {
@@ -924,10 +932,6 @@ static int dps310_fill_channels(struct dps310_data *data,
 	}
 
 	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)
@@ -1017,6 +1021,12 @@ static int dps310_probe(struct i2c_client *client)
 	if (rc)
 		return rc;
 
+	/* Pressure compensation needs a temperature from the start */
+	scoped_guard(mutex, &data->lock)
+		rc = dps310_read_temp_raw_locked(data);
+	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

base-commit: 9752760146e642f3e4a2ec860f8767fa72030d2c
-- 
2.43.0