[media] au8522: fix clamp control for different video modes

Straighten out the clamp control configurations for the various video modes,
based off of register diffs done against the Hauppauge Windows driver.

This work was sponsored by GetWellNetwork Inc.
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/frontends/au8522_decoder.c

@@ -347,9 +347,11 @@ static void au8522_setup_cvbs_mode(struct au8522_state *state)
 	au8522_writereg(state, AU8522_MODULE_CLOCK_CONTROL_REG0A3H,
 			AU8522_MODULE_CLOCK_CONTROL_REG0A3H_CVBS);
 
+	/* PGA in automatic mode */
 	au8522_writereg(state, AU8522_PGA_CONTROL_REG082H, 0x00);
-	au8522_writereg(state, AU8522_CLAMPING_CONTROL_REG083H, 0x0e);
-	au8522_writereg(state, AU8522_PGA_CONTROL_REG082H, 0x10);
+
+	/* Enable clamping control */
+	au8522_writereg(state, AU8522_CLAMPING_CONTROL_REG083H, 0x00);
 
 	au8522_writereg(state, AU8522_INPUT_CONTROL_REG081H,
 			AU8522_INPUT_CONTROL_REG081H_CVBS_CH1);
@@ -366,14 +368,14 @@ static void au8522_setup_cvbs_tuner_mode(struct au8522_state *state)
 	au8522_writereg(state, AU8522_MODULE_CLOCK_CONTROL_REG0A3H,
 			AU8522_MODULE_CLOCK_CONTROL_REG0A3H_CVBS);
 
-	/* It's not clear why they turn off the PGA before enabling the clamp
-	   control, but the Windows trace does it so we will too... */
+	/* It's not clear why we have to have the PGA in automatic mode while
+	   enabling clamp control, but it's what Windows does */
 	au8522_writereg(state, AU8522_PGA_CONTROL_REG082H, 0x00);
 
 	/* Enable clamping control */
 	au8522_writereg(state, AU8522_CLAMPING_CONTROL_REG083H, 0x0e);
 
-	/* Turn on the PGA */
+	/* Disable automatic PGA (since the CVBS is coming from the tuner) */
 	au8522_writereg(state, AU8522_PGA_CONTROL_REG082H, 0x10);
 
 	/* Set input mode to CVBS on channel 4 with SIF audio input enabled */
@@ -396,7 +398,10 @@ static void au8522_setup_svideo_mode(struct au8522_state *state)
 	au8522_writereg(state, AU8522_INPUT_CONTROL_REG081H,
 			AU8522_INPUT_CONTROL_REG081H_SVIDEO_CH13);
 
-	/* Disable clamping control (required for S-video) */
+	/* PGA in automatic mode */
+	au8522_writereg(state, AU8522_PGA_CONTROL_REG082H, 0x00);
+
+	/* Enable clamping control */
 	au8522_writereg(state, AU8522_CLAMPING_CONTROL_REG083H, 0x00);
 
 	setup_decoder_defaults(state,