staging:iio:hmc5843: Implement timeout in read function

avoid polling data ready bit forever; msleep() may be too long
for high sampling frequencies but the driver interface does not
support buffering

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Shubhrajyoti Datta <shubhrajyoti@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/magnetometer/hmc5843.c b/drivers/staging/iio/magnetometer/hmc5843.c
index c281342899ebcbc64eb7c94ef71b86809f9050f5..79117ad978d10f8cda10a2128ad23dd10ee3ab64 100644 (file)
--- a/drivers/staging/iio/magnetometer/hmc5843.c
+++ b/drivers/staging/iio/magnetometer/hmc5843.c
@@ -26,6 +26,7 @@
 #include <linux/types.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/delay.h>
 
 #define HMC5843_CONFIG_REG_A                   0x00
 #define HMC5843_CONFIG_REG_B                   0x01
@@ -210,11 +211,22 @@ static int hmc5843_read_measurement(struct iio_dev *indio_dev,
        struct i2c_client *client = to_i2c_client(indio_dev->dev.parent);
        struct hmc5843_data *data = iio_priv(indio_dev);
        s32 result;
+       int tries = 150;
 
        mutex_lock(&data->lock);
-       result = i2c_smbus_read_byte_data(client, HMC5843_STATUS_REG);
-       while (!(result & HMC5843_DATA_READY))
-               result = i2c_smbus_read_byte_data(client, HMC5843_STATUS_REG);
+       while (tries-- > 0) {
+               result = i2c_smbus_read_byte_data(client,
+                       HMC5843_STATUS_REG);
+               if (result & HMC5843_DATA_READY)
+                       break;
+               msleep(20);
+       }
+
+       if (tries < 0) {
+               dev_err(&client->dev, "data not ready\n");
+               mutex_unlock(&data->lock);
+               return -EIO;
+       }
 
        result = i2c_smbus_read_word_data(client, address);
        mutex_unlock(&data->lock);