1 files changed, 26 insertions, 6 deletions

diff --git a/drivers/media/common/tuners/xc5000.c b/drivers/media/common/tuners/xc5000.c
index 1e28f7dcb26..aa1b2e844d3 100644
--- a/drivers/media/common/tuners/xc5000.c
+++ b/drivers/media/common/tuners/xc5000.c
@@ -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)
 {
@@ -688,21 +697,32 @@ 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_256:
+                case QAM_AUTO:
                 case QAM_16:
                 case QAM_32:
                 case QAM_64:
                 case QAM_128:
-                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 {