2 files changed, 132 insertions, 126 deletions

diff --git a/drivers/media/dvb/frontends/lgdt330x.c b/drivers/media/dvb/frontends/lgdt330x.c
index 9a354708bd20..db3ef58dafba 100644
--- a/drivers/media/dvb/frontends/lgdt330x.c
+++ b/drivers/media/dvb/frontends/lgdt330x.c
@@ -31,9 +31,6 @@
  *   Air2PC/AirStar 2 ATSC 3rd generation (HD5000)
  *   pcHDTV HD5500
  *
- * TODO:
- * signal strength always returns 0.
- *
  */
 
 #include <linux/kernel.h>
@@ -46,9 +43,13 @@
 #include <asm/byteorder.h>
 
 #include "dvb_frontend.h"
+#include "dvb_math.h"
 #include "lgdt330x_priv.h"
 #include "lgdt330x.h"
 
+/* Use Equalizer Mean Squared Error instead of Phaser Tracker MSE */
+/* #define USE_EQMSE */
+
 static int debug = 0;
 module_param(debug, int, 0644);
 MODULE_PARM_DESC(debug,"Turn on/off lgdt330x frontend debugging (default:off).");
@@ -68,6 +69,7 @@ struct lgdt330x_state
 
         /* Demodulator private data */
         fe_modulation_t current_modulation;
+        u32 snr; /* Result of last SNR calculation */
 
         /* Tuner private data */
         u32 current_frequency;
@@ -543,151 +545,150 @@ static int lgdt3303_read_status(struct dvb_frontend* fe, fe_status_t* status)
         return 0;
 }
 
-static int lgdt330x_read_signal_strength(struct dvb_frontend* fe, u16* strength)
+/* Calculate SNR estimation (scaled by 2^24)
+
+   8-VSB SNR equations from LGDT3302 and LGDT3303 datasheets, QAM
+   equations from LGDT3303 datasheet.  VSB is the same between the '02
+   and '03, so maybe QAM is too?  Perhaps someone with a newer datasheet
+   that has QAM information could verify?
+
+   For 8-VSB: (two ways, take your pick)
+   LGDT3302:
+     SNR_EQ = 10 * log10(25 * 24^2 / EQ_MSE)
+   LGDT3303:
+     SNR_EQ = 10 * log10(25 * 32^2 / EQ_MSE)
+   LGDT3302 & LGDT3303:
+     SNR_PT = 10 * log10(25 * 32^2 / PT_MSE)  (we use this one)
+   For 64-QAM:
+     SNR    = 10 * log10( 688128   / MSEQAM)
+   For 256-QAM:
+     SNR    = 10 * log10( 696320   / MSEQAM)
+
+   We re-write the snr equation as:
+     SNR * 2^24 = 10*(c - intlog10(MSE))
+   Where for 256-QAM, c = log10(696320) * 2^24, and so on. */
+
+static u32 calculate_snr(u32 mse, u32 c)
 {
-        /* not directly available. */
-        *strength = 0;
-        return 0;
+        if (mse == 0) /* No signal */
+                return 0;
+
+        mse = intlog10(mse);
+        if (mse > c) {
+                /* Negative SNR, which is possible, but realisticly the
+                demod will lose lock before the signal gets this bad.  The
+                API only allows for unsigned values, so just return 0 */
+                return 0;
+        }
+        return 10*(c - mse);
 }
 
 static int lgdt3302_read_snr(struct dvb_frontend* fe, u16* snr)
 {
-#ifdef SNR_IN_DB
-        /*
-         * Spec sheet shows formula for SNR_EQ = 10 log10(25 * 24**2 / noise)
-         * and SNR_PH = 10 log10(25 * 32**2 / noise) for equalizer and phase tracker
-         * respectively. The following tables are built on these formulas.
-         * The usual definition is SNR = 20 log10(signal/noise)
-         * If the specification is wrong the value retuned is 1/2 the actual SNR in db.
-         *
-         * This table is a an ordered list of noise values computed by the
-         * formula from the spec sheet such that the index into the table
-         * starting at 43 or 45 is the SNR value in db. There are duplicate noise
-         * value entries at the beginning because the SNR varies more than
-         * 1 db for a change of 1 digit in noise at very small values of noise.
-         *
-         * Examples from SNR_EQ table:
-         * noise SNR
-         *   0    43
-         *   1    42
-         *   2    39
-         *   3    37
-         *   4    36
-         *   5    35
-         *   6    34
-         *   7    33
-         *   8    33
-         *   9    32
-         *   10   32
-         *   11   31
-         *   12   31
-         *   13   30
-         */
-
-        static const u32 SNR_EQ[] =
-                { 1,     2,      2,      2, 3,      3,      4,     4,     5,     7,
-                  9,     11,     13,     17, 21,     26,     33,    41,    52,    65,
-                  81,    102,    129,    162, 204,    257,    323,   406,   511,   644,
-                  810,   1020,   1284,   1616, 2035,   2561,   3224,  4059,  5110,  6433,
-                  8098,  10195,  12835,  16158, 20341,  25608,  32238, 40585, 51094, 64323,
-                  80978, 101945, 128341, 161571, 203406, 256073, 0x40000
-                };
-
-        static const u32 SNR_PH[] =
-                { 1,     2,      2,      2,      3,      3,     4,     5,     6,     8,
-                  10,    12,     15,     19,     23,     29, 37,    46,    58,    73,
-                  91,    115,    144,    182,    229,    288, 362,   456,   574,   722,
-                  909,   1144,   1440,   1813,   2282,   2873, 3617,  4553,  5732,  7216,
-                  9084,  11436,  14396,  18124,  22817,  28724,  36161, 45524, 57312, 72151,
-                  90833, 114351, 143960, 181235, 228161, 0x080000
-                };
-
-        static u8 buf[5];/* read data buffer */
-        static u32 noise;   /* noise value */
-        static u32 snr_db;  /* index into SNR_EQ[] */
         struct lgdt330x_state* state = (struct lgdt330x_state*) fe->demodulator_priv;
+        u8 buf[5];      /* read data buffer */
+        u32 noise;      /* noise value */
+        u32 c;          /* per-modulation SNR calculation constant */
 
-        /* read both equalizer and phase tracker noise data */
-        i2c_read_demod_bytes(state, EQPH_ERR0, buf, sizeof(buf));
-
-        if (state->current_modulation == VSB_8) {
-                /* Equalizer Mean-Square Error Register for VSB */
+        switch(state->current_modulation) {
+        case VSB_8:
+                i2c_read_demod_bytes(state, LGDT3302_EQPH_ERR0, buf, 5);
+#ifdef USE_EQMSE
+                /* Use Equalizer Mean-Square Error Register */
+                /* SNR for ranges from -15.61 to +41.58 */
                 noise = ((buf[0] & 7) << 16) | (buf[1] << 8) | buf[2];
-
-                /*
-                 * Look up noise value in table.
-                 * A better search algorithm could be used...
-                 * watch out there are duplicate entries.
-                 */
-                for (snr_db = 0; snr_db < sizeof(SNR_EQ); snr_db++) {
-                        if (noise < SNR_EQ[snr_db]) {
-                                *snr = 43 - snr_db;
-                                break;
-                        }
-                }
-        } else {
-                /* Phase Tracker Mean-Square Error Register for QAM */
-                noise = ((buf[0] & 7<<3) << 13) | (buf[3] << 8) | buf[4];
-
-                /* Look up noise value in table. */
-                for (snr_db = 0; snr_db < sizeof(SNR_PH); snr_db++) {
-                        if (noise < SNR_PH[snr_db]) {
-                                *snr = 45 - snr_db;
-                                break;
-                        }
-                }
-        }
+                c = 69765745; /* log10(25*24^2)*2^24 */
 #else
-        /* Return the raw noise value */
-        static u8 buf[5];/* read data buffer */
-        static u32 noise;   /* noise value */
-        struct lgdt330x_state* state = (struct lgdt330x_state*) fe->demodulator_priv;
-
-        /* read both equalizer and pase tracker noise data */
-        i2c_read_demod_bytes(state, EQPH_ERR0, buf, sizeof(buf));
-
-        if (state->current_modulation == VSB_8) {
-                /* Phase Tracker Mean-Square Error Register for VSB */
+                /* Use Phase Tracker Mean-Square Error Register */
+                /* SNR for ranges from -13.11 to +44.08 */
                 noise = ((buf[0] & 7<<3) << 13) | (buf[3] << 8) | buf[4];
-        } else {
-
-                /* Carrier Recovery Mean-Square Error for QAM */
-                i2c_read_demod_bytes(state, 0x1a, buf, 2);
+                c = 73957994; /* log10(25*32^2)*2^24 */
+#endif
+                break;
+        case QAM_64:
+        case QAM_256:
+                i2c_read_demod_bytes(state, CARRIER_MSEQAM1, buf, 2);
                 noise = ((buf[0] & 3) << 8) | buf[1];
+                c = state->current_modulation == QAM_64 ? 97939837 : 98026066;
+                /* log10(688128)*2^24 and log10(696320)*2^24 */
+                break;
+        default:
+                printk(KERN_ERR "lgdt330x: %s: Modulation set to unsupported value\n",
+                       __FUNCTION__);
+                return -EREMOTEIO; /* return -EDRIVER_IS_GIBBERED; */
         }
 
-        /* Small values for noise mean signal is better so invert noise */
-        *snr = ~noise;
-#endif
+        state->snr = calculate_snr(noise, c);
+        *snr = (state->snr) >> 16; /* Convert from 8.24 fixed-point to 8.8 */
 
-        dprintk("%s: noise = 0x%05x, snr = %idb\n",__FUNCTION__, noise, *snr);
+        dprintk("%s: noise = 0x%08x, snr = %d.%02d dB\n", __FUNCTION__, noise,
+                state->snr >> 24, (((state->snr>>8) & 0xffff) * 100) >> 16);
 
         return 0;
 }
 
 static int lgdt3303_read_snr(struct dvb_frontend* fe, u16* snr)
 {
-        /* Return the raw noise value */
-        static u8 buf[5];/* read data buffer */
-        static u32 noise;   /* noise value */
         struct lgdt330x_state* state = (struct lgdt330x_state*) fe->demodulator_priv;
+        u8 buf[5];      /* read data buffer */
+        u32 noise;      /* noise value */
+        u32 c;          /* per-modulation SNR calculation constant */
 
-        if (state->current_modulation == VSB_8) {
-
-                i2c_read_demod_bytes(state, 0x6e, buf, 5);
-                /* Phase Tracker Mean-Square Error Register for VSB */
+        switch(state->current_modulation) {
+        case VSB_8:
+                i2c_read_demod_bytes(state, LGDT3303_EQPH_ERR0, buf, 5);
+#ifdef USE_EQMSE
+                /* Use Equalizer Mean-Square Error Register */
+                /* SNR for ranges from -16.12 to +44.08 */
+                noise = ((buf[0] & 0x78) << 13) | (buf[1] << 8) | buf[2];
+                c = 73957994; /* log10(25*32^2)*2^24 */
+#else
+                /* Use Phase Tracker Mean-Square Error Register */
+                /* SNR for ranges from -13.11 to +44.08 */
                 noise = ((buf[0] & 7) << 16) | (buf[3] << 8) | buf[4];
-        } else {
-
-                /* Carrier Recovery Mean-Square Error for QAM */
-                i2c_read_demod_bytes(state, 0x1a, buf, 2);
+                c = 73957994; /* log10(25*32^2)*2^24 */
+#endif
+                break;
+        case QAM_64:
+        case QAM_256:
+                i2c_read_demod_bytes(state, CARRIER_MSEQAM1, buf, 2);
                 noise = (buf[0] << 8) | buf[1];
+                c = state->current_modulation == QAM_64 ? 97939837 : 98026066;
+                /* log10(688128)*2^24 and log10(696320)*2^24 */
+                break;
+        default:
+                printk(KERN_ERR "lgdt330x: %s: Modulation set to unsupported value\n",
+                       __FUNCTION__);
+                return -EREMOTEIO; /* return -EDRIVER_IS_GIBBERED; */
         }
 
-        /* Small values for noise mean signal is better so invert noise */
-        *snr = ~noise;
+        state->snr = calculate_snr(noise, c);
+        *snr = (state->snr) >> 16; /* Convert from 8.24 fixed-point to 8.8 */
+
+        dprintk("%s: noise = 0x%08x, snr = %d.%02d dB\n", __FUNCTION__, noise,
+                state->snr >> 24, (((state->snr >> 8) & 0xffff) * 100) >> 16);
+
+        return 0;
+}
+
+static int lgdt330x_read_signal_strength(struct dvb_frontend* fe, u16* strength)
+{
+        /* Calculate Strength from SNR up to 35dB */
+        /* Even though the SNR can go higher than 35dB, there is some comfort */
+        /* factor in having a range of strong signals that can show at 100%   */
+        struct lgdt330x_state* state = (struct lgdt330x_state*) fe->demodulator_priv;
+        u16 snr;
+        int ret;
 
-        dprintk("%s: noise = 0x%05x, snr = %idb\n",__FUNCTION__, noise, *snr);
+        ret = fe->ops.read_snr(fe, &snr);
+        if (ret != 0)
+                return ret;
+        /* Rather than use the 8.8 value snr, use state->snr which is 8.24 */
+        /* scale the range 0 - 35*2^24 into 0 - 65535 */
+        if (state->snr >= 8960 * 0x10000)
+                *strength = 0xffff;
+        else
+                *strength = state->snr / 8960;
 
         return 0;
 }
diff --git a/drivers/media/dvb/frontends/lgdt330x_priv.h b/drivers/media/dvb/frontends/lgdt330x_priv.h
index 59b7c5b9012d..38c76695abfe 100644
--- a/drivers/media/dvb/frontends/lgdt330x_priv.h
+++ b/drivers/media/dvb/frontends/lgdt330x_priv.h
@@ -51,14 +51,19 @@ enum I2C_REG {
         AGC_RFIF_ACC2= 0x3b,
         AGC_STATUS= 0x3f,
         SYNC_STATUS_VSB= 0x43,
-        EQPH_ERR0= 0x47,
-        EQ_ERR1= 0x48,
-        EQ_ERR2= 0x49,
-        PH_ERR1= 0x4a,
-        PH_ERR2= 0x4b,
         DEMUX_CONTROL= 0x66,
+        LGDT3302_EQPH_ERR0= 0x47,
+        LGDT3302_EQ_ERR1= 0x48,
+        LGDT3302_EQ_ERR2= 0x49,
+        LGDT3302_PH_ERR1= 0x4a,
+        LGDT3302_PH_ERR2= 0x4b,
         LGDT3302_PACKET_ERR_COUNTER1= 0x6a,
         LGDT3302_PACKET_ERR_COUNTER2= 0x6b,
+        LGDT3303_EQPH_ERR0= 0x6e,
+        LGDT3303_EQ_ERR1= 0x6f,
+        LGDT3303_EQ_ERR2= 0x70,
+        LGDT3303_PH_ERR1= 0x71,
+        LGDT3303_PH_ERR2= 0x72,
         LGDT3303_PACKET_ERR_COUNTER1= 0x8b,
         LGDT3303_PACKET_ERR_COUNTER2= 0x8c,
 };