cxd2820r: by default SNR output is scaled to full 0-65535 range;
output in dBx10 can be enabled through a module parameter;

Signed-off-by: Gianluca Gennari <gennarone@gmail.com>
---
 drivers/media/dvb-frontends/cxd2820r_core.c |    4 ++++
 drivers/media/dvb-frontends/cxd2820r_priv.h |    1 +
 drivers/media/dvb-frontends/cxd2820r_t.c    |   27 ++++++++++++++++++++++-
 drivers/media/dvb-frontends/cxd2820r_t2.c   |   31 ++++++++++++++++++++++++++-
 4 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/drivers/media/dvb-frontends/cxd2820r_core.c b/drivers/media/dvb-frontends/cxd2820r_core.c
index 9b658c1..35477aa 100644
--- a/drivers/media/dvb-frontends/cxd2820r_core.c
+++ b/drivers/media/dvb-frontends/cxd2820r_core.c
@@ -21,6 +21,10 @@
 
 #include "cxd2820r_priv.h"
 
+int cxd2820r_snrdb;
+module_param_named(snrdb,cxd2820r_snrdb, int, 0644);
+MODULE_PARM_DESC(snrdb, "Turn on/off SNR output in dBx10 (default:off).");
+
 /* write multiple registers */
 static int cxd2820r_wr_regs_i2c(struct cxd2820r_priv *priv, u8 i2c, u8 reg,
 	u8 *val, int len)
diff --git a/drivers/media/dvb-frontends/cxd2820r_priv.h b/drivers/media/dvb-frontends/cxd2820r_priv.h
index 7ff5f60..f742169 100644
--- a/drivers/media/dvb-frontends/cxd2820r_priv.h
+++ b/drivers/media/dvb-frontends/cxd2820r_priv.h
@@ -55,6 +55,7 @@ struct cxd2820r_priv {
 /* cxd2820r_core.c */
 
 extern int cxd2820r_debug;
+extern int cxd2820r_snrdb;
 
 int cxd2820r_gpio(struct dvb_frontend *fe, u8 *gpio);
 
diff --git a/drivers/media/dvb-frontends/cxd2820r_t.c b/drivers/media/dvb-frontends/cxd2820r_t.c
index fa184ca..4268c53 100644
--- a/drivers/media/dvb-frontends/cxd2820r_t.c
+++ b/drivers/media/dvb-frontends/cxd2820r_t.c
@@ -317,7 +317,7 @@ int cxd2820r_read_snr_t(struct dvb_frontend *fe, u16 *snr)
 	struct cxd2820r_priv *priv = fe->demodulator_priv;
 	int ret;
 	u8 buf[2];
-	u16 tmp;
+	u16 tmp, max_snr;
 	/* report SNR in dB * 10 */
 
 	ret = cxd2820r_rd_regs(priv, 0x00028, buf, sizeof(buf));
@@ -332,6 +332,31 @@ int cxd2820r_read_snr_t(struct dvb_frontend *fe, u16 *snr)
 	else
 		*snr = 0;
 
+	if (cxd2820r_snrdb)
+		goto db_out;
+
+	/* scale SNR to full range */
+	ret = cxd2820r_rd_regs(priv, 0x0002f, buf, 1);
+	if (ret)
+		goto error;
+
+	switch ((buf[0] >> 6) & 0x03) {
+	case 0: /* QPSK */
+		max_snr = 230;
+		break;
+	case 1: /* QAM_16 */
+		max_snr = 260;
+		break;
+	case 2: /* QAM_64 */
+	default:
+		max_snr = 290;
+		break;
+	}
+
+	*snr = (*snr >= max_snr) ? 0xffff : (0xffff / max_snr) * *snr;
+	dev_dbg(&priv->i2c->dev, "%s: SNR=%d val=%04x", __func__, *snr, tmp);
+	return ret;
+db_out:
 	dev_dbg(&priv->i2c->dev, "%s: dBx10=%d val=%04x\n", __func__, *snr,
 			tmp);
 
diff --git a/drivers/media/dvb-frontends/cxd2820r_t2.c b/drivers/media/dvb-frontends/cxd2820r_t2.c
index e82d82a..69945cc 100644
--- a/drivers/media/dvb-frontends/cxd2820r_t2.c
+++ b/drivers/media/dvb-frontends/cxd2820r_t2.c
@@ -351,7 +351,7 @@ int cxd2820r_read_snr_t2(struct dvb_frontend *fe, u16 *snr)
 	struct cxd2820r_priv *priv = fe->demodulator_priv;
 	int ret;
 	u8 buf[2];
-	u16 tmp;
+	u16 tmp, max_snr;
 	/* report SNR in dB * 10 */
 
 	ret = cxd2820r_rd_regs(priv, 0x02028, buf, sizeof(buf));
@@ -366,6 +366,35 @@ int cxd2820r_read_snr_t2(struct dvb_frontend *fe, u16 *snr)
 	else
 		*snr = 0;
 
+	if (cxd2820r_snrdb)
+		goto db_out;
+
+	/* scale SNR to full range */
+	ret = cxd2820r_rd_regs(priv, 0x0205d, buf, 1);
+	if (ret)
+		goto error;
+
+	switch (buf[0] & 0x07) {
+	/* FIXME: check the values */
+	case 0: /* QPSK */
+		max_snr = 170;
+		break;
+	case 1: /* QAM_16 */
+		max_snr = 200;
+		break;
+	case 2: /* QAM_64 */
+		max_snr = 230;
+		break;
+	case 3: /* QAM_256 */
+	default:
+		max_snr = 260;
+		break;
+	}
+
+	*snr = (*snr >= max_snr) ? 0xffff : (0xffff / max_snr) * *snr;
+	dev_dbg(&priv->i2c->dev, "%s: SNR=%d val=%04x", __func__, *snr, tmp);
+	return ret;
+db_out:
 	dev_dbg(&priv->i2c->dev, "%s: dBx10=%d val=%04x\n", __func__, *snr,
 			tmp);
 
-- 
1.7.9.5