media: i2c: adv7180: fix reserved bit in Video Selection 2

This bit is marked as reserved in the ADV Hardware Reference Manual.

Resetting this bit seems to cause increased video noise. Setting this
bit according to the Hardware Reference Manual reduces the video noise
immediately.
Signed-off-by: Benjamin Marty <info@benjaminmarty.ch>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Tested-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/i2c/adv7180.c

@@ -43,6 +43,7 @@
 #define ADV7180_INPUT_CONTROL_INSEL_MASK		0x0f
 
 #define ADV7182_REG_INPUT_VIDSEL			0x0002
+#define ADV7182_REG_INPUT_RESERVED			BIT(2)
 
 #define ADV7180_REG_OUTPUT_CONTROL			0x0003
 #define ADV7180_REG_EXTENDED_OUTPUT_CONTROL		0x0004
@@ -1060,7 +1061,9 @@ static int adv7182_init(struct adv7180_state *state)
 
 static int adv7182_set_std(struct adv7180_state *state, unsigned int std)
 {
-	return adv7180_write(state, ADV7182_REG_INPUT_VIDSEL, std << 4);
+	/* Failing to set the reserved bit can result in increased video noise */
+	return adv7180_write(state, ADV7182_REG_INPUT_VIDSEL,
+			     (std << 4) | ADV7182_REG_INPUT_RESERVED);
 }
 
 enum adv7182_input_type {