V4L/DVB (5362): Dvb-pll: add code for doing tuner initialization

Some tuners need or benefit from initialization, to change certain
settings from their power on default values.

Typically, tuners with TUA603x PLLs can benefit from setting the AGC TOP
value to something else.  This patch includes code to set the AGC TOP to
103 dBuV for the Thomson DTT-761x tuners, which I have experimentally
verified gives the best SNR readings, increasing SNR by about 0.19 dB
over the default value.

Other tuners can make use of this as well.  For example, the separate LG
TDVS-H06xF driver's only difference from dvb-pll is this same setting of
AGC TOP value.
Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/dvb/frontends/dvb-pll.c

@@ -27,6 +27,17 @@
 /* ----------------------------------------------------------- */
 /* descriptions                                                */
 
+/* Set AGC TOP value to 103 dBuV:
+	0x80 = Control Byte
+	0x40 = 250 uA charge pump (irrelevant)
+	0x18 = Aux Byte to follow
+	0x06 = 64.5 kHz divider (irrelevant)
+	0x01 = Disable Vt (aka sleep)
+
+	0x00 = AGC Time constant 2s Iagc = 300 nA (vs 0x80 = 9 nA)
+	0x50 = AGC Take over point = 103 dBuV */
+static u8 tua603x_agc103[] = { 2, 0x80|0x40|0x18|0x06|0x01, 0x00|0x50 };
+
 struct dvb_pll_desc dvb_pll_thomson_dtt7579 = {
 	.name  = "Thomson dtt7579",
 	.min   = 177000000,
@@ -113,6 +124,7 @@ struct dvb_pll_desc dvb_pll_thomson_dtt761x = {
 	.min   =  57000000,
 	.max   = 863000000,
 	.count = 3,
+	.initdata = tua603x_agc103,
 	.entries = {
 		{ 147000000, 44000000, 62500, 0x8e, 0x39 },
 		{ 417000000, 44000000, 62500, 0x8e, 0x3a },
@@ -599,6 +611,31 @@ static int dvb_pll_get_bandwidth(struct dvb_frontend *fe, u32 *bandwidth)
 	return 0;
 }
 
+static int dvb_pll_init(struct dvb_frontend *fe)
+{
+	struct dvb_pll_priv *priv = fe->tuner_priv;
+
+	if (priv->i2c == NULL)
+		return -EINVAL;
+
+	if (priv->pll_desc->initdata) {
+		struct i2c_msg msg = { .flags = 0,
+			.addr = priv->pll_i2c_address,
+			.buf = priv->pll_desc->initdata + 1,
+			.len = priv->pll_desc->initdata[0] };
+
+		int result;
+		if (fe->ops.i2c_gate_ctrl)
+			fe->ops.i2c_gate_ctrl(fe, 1);
+		if ((result = i2c_transfer(priv->i2c, &msg, 1)) != 1) {
+			return result;
+		}
+		return 0;
+	}
+	/* Shouldn't be called when initdata is NULL, maybe BUG()? */
+	return -EINVAL;
+}
+
 static struct dvb_tuner_ops dvb_pll_tuner_ops = {
 	.release = dvb_pll_release,
 	.sleep = dvb_pll_sleep,
@@ -644,6 +681,8 @@ struct dvb_frontend *dvb_pll_attach(struct dvb_frontend *fe, int pll_addr,
 		sizeof(fe->ops.tuner_ops.info.name));
 	fe->ops.tuner_ops.info.frequency_min = desc->min;
 	fe->ops.tuner_ops.info.frequency_min = desc->max;
+	if (desc->initdata)
+		fe->ops.tuner_ops.init = dvb_pll_init;
 
 	fe->tuner_priv = priv;
 	return fe;

drivers/media/dvb/frontends/dvb-pll.h

@@ -13,6 +13,7 @@ struct dvb_pll_desc {
 	u32  min;
 	u32  max;
 	void (*setbw)(u8 *buf, u32 freq, int bandwidth);
+	u8   *initdata;
 	int  count;
 	struct {
 		u32 limit;