[media] it913x-fe ver 1.15 read signal strenght using reg VAR_P_INBAND

Read signal strength using VAR_P_INBAND and apply FEC preferred values.

Note this does not work on IT9137 devices even with dvb-usb-it9135-01.fw
firmware.

Config read_sl allows switch between read signal strength and signal
level.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 81 insertions, 10 deletions

diff --git a/drivers/media/dvb/frontends/it913x-fe.c b/drivers/media/dvb/frontends/it913x-fe.c
index ccc36bf2deb..84df03c2917 100644
--- a/drivers/media/dvb/frontends/it913x-fe.c
+++ b/drivers/media/dvb/frontends/it913x-fe.c
@@ -57,6 +57,7 @@ struct it913x_fe_state {
         u32 frequency;
         fe_modulation_t constellation;
         fe_transmit_mode_t transmission_mode;
+        u8 priority;
         u32 crystalFrequency;
         u32 adcFrequency;
         u8 tuner_type;
@@ -500,19 +501,87 @@ static int it913x_fe_read_status(struct dvb_frontend *fe, fe_status_t *status)
         return 0;
 }
 
+/* FEC values based on fe_code_rate_t non supported values 0*/
+int it913x_qpsk_pval[] = {0, -93, -91, -90, 0, -89, -88};
+int it913x_16qam_pval[] = {0, -87, -85, -84, 0, -83, -82};
+int it913x_64qam_pval[] = {0, -82, -80, -78, 0, -77, -76};
+
+static int it913x_get_signal_strength(struct dvb_frontend *fe)
+{
+        struct dtv_frontend_properties *p = &fe->dtv_property_cache;
+        struct it913x_fe_state *state = fe->demodulator_priv;
+        u8 code_rate;
+        int ret, temp;
+        u8 lna_gain_os;
+
+        ret = it913x_read_reg_u8(state, VAR_P_INBAND);
+        if (ret < 0)
+                return ret;
+
+        /* VHF/UHF gain offset */
+        if (state->frequency < 300000000)
+                lna_gain_os = 7;
+        else
+                lna_gain_os = 14;
+
+        temp = (ret - 100) - lna_gain_os;
+
+        if (state->priority == PRIORITY_HIGH)
+                code_rate = p->code_rate_HP;
+        else
+                code_rate = p->code_rate_LP;
+
+        if (code_rate >= ARRAY_SIZE(it913x_qpsk_pval))
+                return -EINVAL;
+
+        deb_info("Reg VAR_P_INBAND:%d Calc Offset Value:%d", ret, temp);
+
+        /* Apply FEC offset values*/
+        switch (p->modulation) {
+        case QPSK:
+                temp -= it913x_qpsk_pval[code_rate];
+                break;
+        case QAM_16:
+                temp -= it913x_16qam_pval[code_rate];
+                break;
+        case QAM_64:
+                temp -= it913x_64qam_pval[code_rate];
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        if (temp < -15)
+                ret = 0;
+        else if ((-15 <= temp) && (temp < 0))
+                ret = (2 * (temp + 15)) / 3;
+        else if ((0 <= temp) && (temp < 20))
+                ret = 4 * temp + 10;
+        else if ((20 <= temp) && (temp < 35))
+                ret = (2 * (temp - 20)) / 3 + 90;
+        else if (temp >= 35)
+                ret = 100;
+
+        deb_info("Signal Strength :%d", ret);
+
+        return ret;
+}
+
 static int it913x_fe_read_signal_strength(struct dvb_frontend *fe,
                 u16 *strength)
 {
         struct it913x_fe_state *state = fe->demodulator_priv;
-        int ret = it913x_read_reg_u8(state, SIGNAL_LEVEL);
-        /*SIGNAL_LEVEL always returns 100%! so using FE_HAS_SIGNAL as switch*/
-        if (state->it913x_status & FE_HAS_SIGNAL)
-                ret = (ret * 0xff) / 0x64;
-        else
-                ret = 0x0;
-        ret |= ret << 0x8;
-        *strength = ret;
-        return 0;
+        int ret = 0;
+        if (state->config->read_slevel) {
+                if (state->it913x_status & FE_HAS_SIGNAL)
+                        ret = it913x_read_reg_u8(state, SIGNAL_LEVEL);
+        } else
+                ret = it913x_get_signal_strength(fe);
+
+        if (ret >= 0)
+                *strength = (u16)((u32)ret * 0xffff / 0x64);
+
+        return (ret < 0) ? -ENODEV : 0;
 }
 
 static int it913x_fe_read_snr(struct dvb_frontend *fe, u16 *snr)
@@ -606,6 +675,8 @@ static int it913x_fe_get_frontend(struct dvb_frontend *fe)
         if (reg[2] < 4)
                 p->hierarchy = fe_hi[reg[2]];
 
+        state->priority = reg[5];
+
         p->code_rate_HP = (reg[6] < 6) ? fe_code[reg[6]] : FEC_NONE;
         p->code_rate_LP = (reg[7] < 6) ? fe_code[reg[7]] : FEC_NONE;
 
@@ -972,5 +1043,5 @@ static struct dvb_frontend_ops it913x_fe_ofdm_ops = {
 
 MODULE_DESCRIPTION("it913x Frontend and it9137 tuner");
 MODULE_AUTHOR("Malcolm Priestley tvboxspy@gmail.com");
-MODULE_VERSION("1.13");
+MODULE_VERSION("1.15");
 MODULE_LICENSE("GPL");