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>

2 files changed, 8 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);
diff --git a/drivers/media/common/tuners/mxl5005s.h b/drivers/media/common/tuners/mxl5005s.h
index 7ac6815b30aa..fc8a1ffc53b4 100644
--- a/drivers/media/common/tuners/mxl5005s.h
+++ b/drivers/media/common/tuners/mxl5005s.h
@@ -108,6 +108,10 @@ struct mxl5005s_config {
 #define MXL_LOW_IF  1
         u8 if_mode;
 
+        /* Some boards need to override the built-in logic for determining
+           the gain when in QAM mode (the HVR-1600 is one such case) */
+        u8 qam_gain;
+
         /* Stuff I don't know what to do with */
         u8 AgcMasterByte;
 };