V4L/DVB (13331): mxl5005s: provide ability to override QAM gain for HVR-1600

The HVR-1600 doesn't use the standard mechanism for computing the gain when
in QAM mode, instead always forcing it to be 0x02.  Provide the ability to
override the algorithm on a per-board basis.

This change results in an improvement of 0.4-0.6 dB for QAM tuning.

This work was sponsored by ONELAN Limited.

Cc: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/media/common/tuners/mxl5005s.c b/drivers/media/common/tuners/mxl5005s.c
index 0803dab58fff..605e28b73263 100644
--- a/drivers/media/common/tuners/mxl5005s.c
+++ b/drivers/media/common/tuners/mxl5005s.c
@@ -2789,7 +2789,10 @@ static u16 MXL_TuneRF(struct dvb_frontend *fe, u32 RF_Freq)
 
         /* add for 2.6.5 Special setting for QAM */
         if (state->Mod_Type == MXL_QAM) {
-                if (state->RF_IN < 680000000)
+                if (state->config->qam_gain != 0)
+                        status += MXL_ControlWrite(fe, RFSYN_CHP_GAIN,
+                                                   state->config->qam_gain);
+                else if (state->RF_IN < 680000000)
                         status += MXL_ControlWrite(fe, RFSYN_CHP_GAIN, 3);
                 else
                         status += MXL_ControlWrite(fe, RFSYN_CHP_GAIN, 2);