[PATCH v3 6/6] iio: magnetometer: ak8975: modernize polling loops with iopoll() macros

[Joshua Crofts <joshua.crofts1@gmail.com>]

The driver currently uses while loops and msleep() for polling during
conversion waits.

Replace the custom polling loops with readx_poll_timeout() and
read_poll_timeout() macros from <linux/iopoll.h>. This reduces
boilerplate, standardizes timeout handling and improves overall code
readability, keeping the original timing and error behaviour. Add
<linux/time.h> for USEC_PER_MSEC macro instead of using magic numbers.

Assisted-by: Gemini:3.1-Pro
Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
---
 drivers/iio/magnetometer/ak8975.c | 47 ++++++++++++++-----------------
 1 file changed, 21 insertions(+), 26 deletions(-)

diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
index 723c2f64b8e..0724569e766 100644
--- a/drivers/iio/magnetometer/ak8975.c
+++ b/drivers/iio/magnetometer/ak8975.c
@@ -15,6 +15,7 @@
 #include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
+#include <linux/iopoll.h>
 #include <linux/irqreturn.h>
 #include <linux/minmax.h>
 #include <linux/mod_devicetable.h>
@@ -23,6 +24,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/property.h>
 #include <linux/regulator/consumer.h>
+#include <linux/time.h>
 #include <linux/types.h>
 #include <linux/wait.h>
 
@@ -652,18 +654,16 @@ static int ak8975_setup(struct i2c_client *client)
 static int wait_conversion_complete_gpio(struct ak8975_data *data)
 {
 	struct i2c_client *client = data->client;
-	u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 	int ret;
+	int val;
 
 	/* Wait for the conversion to complete. */
-	while (timeout_ms) {
-		msleep(AK8975_CONVERSION_DONE_POLL_TIME);
-		if (gpiod_get_value(data->eoc_gpiod))
-			break;
-		timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
-	}
-	if (!timeout_ms)
-		return -ETIMEDOUT;
+	ret = readx_poll_timeout(gpiod_get_value, data->eoc_gpiod, val,
+				 val != 0,
+				 AK8975_CONVERSION_DONE_POLL_TIME * USEC_PER_MSEC,
+				 AK8975_MAX_CONVERSION_TIMEOUT * USEC_PER_MSEC);
+	if (ret)
+		return ret;
 
 	ret = i2c_smbus_read_byte_data(client, data->def->ctrl_regs[ST1]);
 	if (ret < 0)
@@ -675,28 +675,23 @@ static int wait_conversion_complete_gpio(struct ak8975_data *data)
 static int wait_conversion_complete_polled(struct ak8975_data *data)
 {
 	struct i2c_client *client = data->client;
-	u8 read_status;
-	u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 	int ret;
+	int val;
 
 	/* Wait for the conversion to complete. */
-	while (timeout_ms) {
-		msleep(AK8975_CONVERSION_DONE_POLL_TIME);
-		ret = i2c_smbus_read_byte_data(client,
-					       data->def->ctrl_regs[ST1]);
-		if (ret < 0) {
-			dev_err(&client->dev, "Error in reading ST1\n");
-			return ret;
-		}
-		read_status = ret;
-		if (read_status)
-			break;
-		timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
+	ret = read_poll_timeout(i2c_smbus_read_byte_data, val, val != 0,
+				AK8975_CONVERSION_DONE_POLL_TIME * USEC_PER_MSEC,
+				AK8975_MAX_CONVERSION_TIMEOUT * USEC_PER_MSEC,
+				true,
+				client, data->def->ctrl_regs[ST1]);
+	if (ret)
+		return ret;
+	if (val < 0) {
+		dev_err(&client->dev, "Error in reading ST1\n");
+		return val;
 	}
-	if (!timeout_ms)
-		return -ETIMEDOUT;
 
-	return read_status;
+	return val;
 }
 
 /* Returns 0 if the end of conversion interrupt occurred or -ETIME otherwise */
-- 
2.47.3