media: adv7180: fix field type to V4L2_FIELD_ALTERNATE

The ADV7180 and ADV7182 transmit whole fields, bottom field followed
by top (or vice-versa, depending on detected video standard). So
for chips that do not have support for explicitly setting the field
mode via I2P, set the field mode to V4L2_FIELD_ALTERNATE.

I2P converts fields into frames using an edge adaptive algorithm. The
frame rate is the same as the 'field rate': e.g. X fields per second
are now X frames per second.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/i2c/adv7180.c

@@ -644,6 +644,9 @@ static int adv7180_mbus_fmt(struct v4l2_subdev *sd,
 	fmt->width = 720;
 	fmt->height = state->curr_norm & V4L2_STD_525_60 ? 480 : 576;
 
+	if (state->field == V4L2_FIELD_ALTERNATE)
+		fmt->height /= 2;
+
 	return 0;
 }
 
@@ -711,11 +714,11 @@ static int adv7180_set_pad_format(struct v4l2_subdev *sd,
 
 	switch (format->format.field) {
 	case V4L2_FIELD_NONE:
-		if (!(state->chip_info->flags & ADV7180_FLAG_I2P))
-			format->format.field = V4L2_FIELD_INTERLACED;
+		if (state->chip_info->flags & ADV7180_FLAG_I2P)
 			break;
+		/* fall through */
 	default:
-		format->format.field = V4L2_FIELD_INTERLACED;
+		format->format.field = V4L2_FIELD_ALTERNATE;
 		break;
 	}
 
@@ -1291,7 +1294,7 @@ static int adv7180_probe(struct i2c_client *client,
 		return -ENOMEM;
 
 	state->client = client;
-	state->field = V4L2_FIELD_INTERLACED;
+	state->field = V4L2_FIELD_ALTERNATE;
 	state->chip_info = (struct adv7180_chip_info *)id->driver_data;
 
 	state->pwdn_gpio = devm_gpiod_get_optional(&client->dev, "powerdown",