dtv_demod: txlx atsc-t loses lock when play video for a long time [1/1]

PD#SWPL-3418

Problem:
[Einstein]when AC off/on,enter live TV ,
TV display blank screen and no signal about 5S

Solution:
use post-eq to track(0x912=0x50)

Verify:
verified by t962x_r311

Change-Id: I924c55a8f1c92328e4371cb730e1b03bd720457f
Signed-off-by: Zhiwei Yuan <zhiwei.yuan@amlogic.com>

drivers/amlogic/media/dtv_demod/amlfrontend.c

@@ -1952,6 +1952,9 @@ void atsc_polling(struct dvb_frontend *fe, enum fe_status *status)
 {
 	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
 
+	if (!demod_thread)
+		return;
+
 	if (c->modulation == QPSK) {
 		PR_DBG("mode is qpsk, return;\n");
 		/*return;*/
@@ -2515,6 +2518,9 @@ static int gxtv_demod_dvbc_tune(struct dvb_frontend *fe, bool re_tune,
 
 	*delay = HZ / 4;
 
+	if (!demod_thread)
+		return 0;
+
 	if (re_tune) {
 		/*first*/
 		dtvdd_devp->en_detect = 1;

drivers/amlogic/media/dtv_demod/atsc_func.c

@@ -565,6 +565,7 @@ if (!field_test_version) {
 	atsc_write_reg(0x54d, 0x08);
 	atsc_write_reg(0x54c, 0x08);
 	atsc_write_reg(0x53b, 0x0e);
+	atsc_write_reg(0x912, 0x50);
 }
 	ar_flag = 0;
 }