Input: iqs5xx - allow more time for ATI to complete

After the device is initialized, it runs ATI (calibration) during
which it cannot readily respond to I2C communication. To keep the
open and close callbacks from writing to the device too soon, the
driver waits 100 ms before returning from probe.

The vendor reports that ATI may actually take up to 250 ms to run
(including margin), so increase the delay accordingly. Update the
comments to clarify the reason for the delay as well.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Link: https://lore.kernel.org/r/1611002626-5889-9-git-send-email-jeff@labundy.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/iqs5xx.c

@@ -643,13 +643,12 @@ static int iqs5xx_dev_init(struct i2c_client *client)
 	iqs5xx->bl_status = dev_id_info->bl_status;
 
 	/*
-	 * Closure of the first communication window that appears following the
-	 * release of reset appears to kick off an initialization period during
-	 * which further communication is met with clock stretching. The return
-	 * from this function is delayed so that further communication attempts
-	 * avoid this period.
+	 * The following delay allows ATI to complete before the open and close
+	 * callbacks are free to elicit I2C communication. Any attempts to read
+	 * from or write to the device during this time may face extended clock
+	 * stretching and prompt the I2C controller to report an error.
 	 */
-	msleep(100);
+	msleep(250);
 
 	return 0;
 }