media: dvb_frontend: add missing DSS switch cases

While the documentation mentions the delivery system DSS as a satellite
system, it was missing from all but one switch statement in the DVB
frontend code, leading to tuning failures, because the frequency was not
correctly handled as being in kHz rather than Hz.

Add the missing switch cases so that DSS is handled like the other
satellite systems. For the rolloff, assume 0.20 as per one publication
found via Internet search.

Link: https://lore.kernel.org/linux-media/trinity-5f5afda9-657a-4a91-bf15-842f4f249535-1641958421391@3c-app-gmx-bap21
Signed-off-by: Robert Schlabbach <robert_s@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/dvb-core/dvb_frontend.c

@@ -918,6 +918,7 @@ static void dvb_frontend_get_frequency_limits(struct dvb_frontend *fe,
 
 	/* If the standard is for satellite, convert frequencies to kHz */
 	switch (c->delivery_system) {
+	case SYS_DSS:
 	case SYS_DVBS:
 	case SYS_DVBS2:
 	case SYS_TURBO:
@@ -943,6 +944,7 @@ static u32 dvb_frontend_get_stepsize(struct dvb_frontend *fe)
 	u32 step = max(fe_step, tuner_step);
 
 	switch (c->delivery_system) {
+	case SYS_DSS:
 	case SYS_DVBS:
 	case SYS_DVBS2:
 	case SYS_TURBO:
@@ -974,6 +976,7 @@ static int dvb_frontend_check_parameters(struct dvb_frontend *fe)
 
 	/* range check: symbol rate */
 	switch (c->delivery_system) {
+	case SYS_DSS:
 	case SYS_DVBS:
 	case SYS_DVBS2:
 	case SYS_TURBO:
@@ -1040,6 +1043,10 @@ static int dvb_frontend_clear_cache(struct dvb_frontend *fe)
 	c->scrambling_sequence_index = 0;/* default sequence */
 
 	switch (c->delivery_system) {
+	case SYS_DSS:
+		c->modulation = QPSK;
+		c->rolloff = ROLLOFF_20;
+		break;
 	case SYS_DVBS:
 	case SYS_DVBS2:
 	case SYS_TURBO:
@@ -1821,6 +1828,7 @@ static void prepare_tuning_algo_parameters(struct dvb_frontend *fe)
 	} else {
 		/* default values */
 		switch (c->delivery_system) {
+		case SYS_DSS:
 		case SYS_DVBS:
 		case SYS_DVBS2:
 		case SYS_ISDBS:
@@ -2288,6 +2296,9 @@ static int dtv_set_frontend(struct dvb_frontend *fe)
 	case SYS_DVBC_ANNEX_C:
 		rolloff = 113;
 		break;
+	case SYS_DSS:
+		rolloff = 120;
+		break;
 	case SYS_DVBS:
 	case SYS_TURBO:
 	case SYS_ISDBS: