@@ -628,6 +628,15 @@ static void xc_debug_dump(struct xc5000_priv *priv)
dprintk(1, "*** Quality (0:<8dB, 7:>56dB) = %d\n", quality);
}
+/*
+ * As defined on EN 300 429, the DVB-C roll-off factor is 0.15.
+ * So, the amount of the needed bandwith is given by:
+ * Bw = Symbol_rate * (1 + 0.15)
+ * As such, the maximum symbol rate supported by 6 MHz is given by:
+ * max_symbol_rate = 6 MHz / 1.15 = 5217391 Bauds
+ */
+#define MAX_SYMBOL_RATE_6MHz 5217391
+
static int xc5000_set_params(struct dvb_frontend *fe,
struct dvb_frontend_parameters *params)
{
@@ -688,7 +697,6 @@ static int xc5000_set_params(struct dvb_frontend *fe,
}
priv->rf_mode = XC_RF_MODE_AIR;
} else if (fe->ops.info.type == FE_QAM) {
- dprintk(1, "%s() QAM\n", __func__);
switch (params->u.qam.modulation) {
case QAM_16:
case QAM_32:
@@ -697,12 +705,24 @@ static int xc5000_set_params(struct dvb_frontend *fe,
case QAM_256:
case QAM_AUTO:
dprintk(1, "%s() QAM modulation\n", __func__);
- priv->bandwidth = BANDWIDTH_8_MHZ;
- priv->video_standard = DTV7_8;
- priv->freq_hz = params->frequency - 2750000;
priv->rf_mode = XC_RF_MODE_CABLE;
+ /*
+ * Using a 8MHz bandwidth sometimes fail
+ * with 6MHz-spaced channels, due to inter-carrier
+ * interference. So, use DTV6 firmware
+ */
+ if (params->u.qam.symbol_rate <= MAX_SYMBOL_RATE_6MHz) {
+ priv->bandwidth = BANDWIDTH_6_MHZ;
+ priv->video_standard = DTV6;
+ priv->freq_hz = params->frequency - 1750000;
+ } else {
+ priv->bandwidth = BANDWIDTH_8_MHZ;
+ priv->video_standard = DTV7_8;
+ priv->freq_hz = params->frequency - 2750000;
+ }
break;
default:
+ dprintk(1, "%s() Unsupported QAM type\n", __func__);
return -EINVAL;
}
} else {