[PATCH] media: cx231xx: fix si2157 inversion for Hauppauge WinTV-HVR-935C

[PATCH] media: cx231xx: fix si2157 inversion for Hauppauge WinTV-HVR-935C

[Dimitris Kerasiotis]

On the Hauppauge WinTV-HVR-935C (USB ID 2040:b151) the si2157 tuner
is configured with inversion = true. On at least some hardware
revisions (tested: Hauppauge model 111519, rev G2I6) this is wrong:
tuner and demod probe successfully, firmware loads (si2157 patch
3.0.5, si2168 B 4.0.25), signal strength is reported correctly and
the Si2168 briefly reports FE_HAS_SIGNAL | FE_HAS_CARRIER, but it
never achieves lock on any DVB-T mux, on any frequency, regardless
of signal quality (tested down to -48 dBm, C/N 38 dB). The same
unit works under the vendor's Windows driver.

Setting inversion = false results in immediate lock (FE_HAS_LOCK,
postBER 0) and a successful scan of all eight DVB-T muxes receivable
in Attica, Greece. This matches the configuration already used for
the Evromedia Full Hybrid Full HD, which uses the same
cx231xx + si2168 + si2157 chip combination.

Tested on kernels 6.1 and 6.12 with identical results.

Signed-off-by: Dimitris Kerasiotis <dkerasiotis@gmail.com>
---
 drivers/media/usb/cx231xx/cx231xx-dvb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/cx231xx/cx231xx-dvb.c b/drivers/media/usb/cx231xx/cx231xx-dvb.c
index 472a4405a..a5486bcca 100644
--- a/drivers/media/usb/cx231xx/cx231xx-dvb.c
+++ b/drivers/media/usb/cx231xx/cx231xx-dvb.c
@@ -1014,7 +1014,7 @@ static int dvb_init(struct cx231xx *dev)
 		si2157_config.mdev = dev->media_dev;
 #endif
 		si2157_config.if_port = 1;
-		si2157_config.inversion = true;
+		si2157_config.inversion = false;
 
 		/* perform probe/init/attach */
 		client = dvb_module_probe("si2157", NULL, tuner_i2c,
-- 
2.47.3