V4L/DVB (12243): em28xx: allow specifying sensor xtal frequency

In order to properly estimate fps, mt9v011 sensor driver needs to know
what is the used frequency on the sensor cristal. Adds the proper fields
and initialization code for specifying the cristal frequency.

Also, based on experimentation, it was noticed that the Silvercrest is
outputing data at 7 fps. This means that it should be using a 6.3 MHz
cristal. This information needs to be double checked later, by opening
the device. Anyway, by using this value for xtal, at least now we have
the correct fps report.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/em28xx/em28xx-cards.c

@@ -1734,6 +1734,7 @@ static int em28xx_hint_sensor(struct em28xx *dev)
 		dev->em28xx_sensor = EM28XX_MT9V011;
 		dev->sensor_xres = 640;
 		dev->sensor_yres = 480;
+		dev->sensor_xtal = 6300000;
 		break;
 	default:
 		printk("Unknown Micron Sensor 0x%04x\n", be16_to_cpu(version));
@@ -2261,9 +2262,13 @@ void em28xx_card_setup(struct em28xx *dev)
 		v4l2_i2c_new_probed_subdev(&dev->v4l2_dev, &dev->i2c_adap,
 			"tvp5150", "tvp5150", tvp5150_addrs);
 
-	if (dev->em28xx_sensor == EM28XX_MT9V011)
-		v4l2_i2c_new_probed_subdev(&dev->v4l2_dev, &dev->i2c_adap,
-			"mt9v011", "mt9v011", mt9v011_addrs);
+	if (dev->em28xx_sensor == EM28XX_MT9V011) {
+		struct v4l2_subdev *sd;
+
+		sd = v4l2_i2c_new_probed_subdev(&dev->v4l2_dev,
+			 &dev->i2c_adap, "mt9v011", "mt9v011", mt9v011_addrs);
+		v4l2_subdev_call(sd, core, s_config, 0, &dev->sensor_xtal);
+	}
 
 	if (dev->board.adecoder == EM28XX_TVAUDIO)
 		v4l2_i2c_new_subdev(&dev->v4l2_dev, &dev->i2c_adap,

drivers/media/video/em28xx/em28xx.h

@@ -478,8 +478,10 @@ struct em28xx {
 	struct v4l2_device v4l2_dev;
 	struct em28xx_board board;
 
+	/* Webcam specific fields */
 	enum em28xx_sensor em28xx_sensor;
 	int sensor_xres, sensor_yres;
+	int sensor_xtal;
 
 	unsigned int stream_on:1;	/* Locks streams */
 	unsigned int has_audio_class:1;