[PATCH 11/15] si2165: add DVBv5 C/N statistics for DVB-C

[Matthias Schwarzott]

Add C/N statistics in dB to read_status (DVBv5).

Signed-off-by: Matthias Schwarzott <z...@gentoo.org>
---
 drivers/media/dvb-frontends/si2165.c      | 43 +++++++++++++++++++++++++++++--
 drivers/media/dvb-frontends/si2165_priv.h |  1 +
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/drivers/media/dvb-frontends/si2165.c 
b/drivers/media/dvb-frontends/si2165.c
index 30ceba664f5f..777b7d049ae7 100644
--- a/drivers/media/dvb-frontends/si2165.c
+++ b/drivers/media/dvb-frontends/si2165.c
@@ -116,6 +116,17 @@ static int si2165_readreg16(struct si2165_state *state,
        return ret;
 }
 
+static int si2165_readreg24(struct si2165_state *state,
+                           const u16 reg, u32 *val)
+{
+       u8 buf[3];
+
+       int ret = si2165_read(state, reg, buf, 3);
+       *val = buf[0] | buf[1] << 8 | buf[2] << 16;
+       dev_dbg(&state->client->dev, "reg read: R(0x%04x)=0x%06x\n", reg, *val);
+       return ret;
+}
+
 static int si2165_writereg8(struct si2165_state *state, const u16 reg, u8 val)
 {
        return regmap_write(state->regmap, reg, val);
@@ -518,6 +529,7 @@ static int si2165_init(struct dvb_frontend *fe)
 {
        int ret = 0;
        struct si2165_state *state = fe->demodulator_priv;
+       struct dtv_frontend_properties *c = &fe->dtv_property_cache;
        u8 val;
        u8 patch_version = 0x00;
 
@@ -627,6 +639,10 @@ static int si2165_init(struct dvb_frontend *fe)
        if (ret < 0)
                return ret;
 
+       c = &state->fe.dtv_property_cache;
+       c->cnr.len = 1;
+       c->cnr.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
+
        return 0;
 error:
        return ret;
@@ -652,9 +668,10 @@ static int si2165_read_status(struct dvb_frontend *fe, 
enum fe_status *status)
 {
        int ret;
        u8 u8tmp;
+       u32 u32tmp;
        struct si2165_state *state = fe->demodulator_priv;
-       struct dtv_frontend_properties *p = &fe->dtv_property_cache;
-       u32 delsys = p->delivery_system;
+       struct dtv_frontend_properties *c = &fe->dtv_property_cache;
+       u32 delsys = c->delivery_system;
 
        *status = 0;
 
@@ -699,6 +716,28 @@ static int si2165_read_status(struct dvb_frontend *fe, 
enum fe_status *status)
                *status |= FE_HAS_LOCK;
        }
 
+       /* CNR */
+       if (delsys == SYS_DVBC_ANNEX_A && *status & FE_HAS_VITERBI) {
+               ret = si2165_readreg24(state, REG_C_N, &u32tmp);
+               if (ret < 0)
+                       return ret;
+               /*
+                * svalue =
+                * 1000 * c_n/dB =
+                * 1000 * 10 * log10(2^24 / regval) =
+                * 1000 * 10 * (log10(2^24) - log10(regval)) =
+                * 1000 * 10 * (intlog10(2^24) - intlog10(regval)) / 2^24
+                *
+                * intlog10(x) = log10(x) * 2^24
+                * intlog10(2^24) = log10(2^24) * 2^24 = 121210686
+                */
+               u32tmp = (1000 * 10 * (121210686 - (u64)intlog10(u32tmp)))
+                               >> 24;
+               c->cnr.stat[0].scale = FE_SCALE_DECIBEL;
+               c->cnr.stat[0].svalue = u32tmp;
+       } else
+               c->cnr.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
+
        return 0;
 }
 
diff --git a/drivers/media/dvb-frontends/si2165_priv.h 
b/drivers/media/dvb-frontends/si2165_priv.h
index 47f18ff69fe5..9d79e86d04c2 100644
--- a/drivers/media/dvb-frontends/si2165_priv.h
+++ b/drivers/media/dvb-frontends/si2165_priv.h
@@ -74,6 +74,7 @@ struct si2165_config {
 #define REG_KP_LOCK                    0x023a
 #define REG_UNKNOWN_24C                        0x024c
 #define REG_CENTRAL_TAP                        0x0261
+#define REG_C_N                                0x026c
 #define REG_EQ_AUTO_CONTROL            0x0278
 #define REG_UNKNOWN_27C                        0x027c
 #define REG_START_SYNCHRO              0x02e0
-- 
2.15.0