linux-kernel - Re: Scanning for TV channels over DVB-T and DVB-T2

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Message-ID: <71c3a7c3-0661-c4ac-6f72-8409fa38211b@free.fr>
Date:   Fri, 19 Jun 2020 22:15:19 +0200
From:   Marc Gonzalez <marc.w.gonzalez@...e.fr>
To:     linux-media <linux-media@...r.kernel.org>,
        Sean Young <sean@...s.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jan Pieter van Woerkom <jp@...w.nl>,
        Brad Love <brad@...tdimension.cc>,
        Antti Palosaari <crope@....fi>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: Scanning for TV channels over DVB-T and DVB-T2

On 10/06/2020 17:22, Marc Gonzalez wrote:

> FTR, on IRC, Brad pointed out this patch of his:
> https://patchwork.kernel.org/patch/10744999/

I suggest the following patch on top of Brad's patch:

Author: Marc Gonzalez <marc.w.gonzalez@...e.fr>
Date:   Fri Jun 19 22:09:26 2020 +0200

    si2168: wait for carrier lock before next step

diff --git a/drivers/media/dvb-frontends/si2168.c b/drivers/media/dvb-frontends/si2168.c
index 31d3dc0216c2..e127e842f671 100644
--- a/drivers/media/dvb-frontends/si2168.c
+++ b/drivers/media/dvb-frontends/si2168.c
@@ -152,6 +152,11 @@ static int si2168_ts_bus_ctrl(struct dvb_frontend *fe, int acquire)
 	return ret;
 }
 
+static bool carrier_locked(struct si2168_cmd *cmd)
+{
+	return cmd->args[2] & BIT(1);
+}
+
 static int si2168_read_status(struct dvb_frontend *fe, enum fe_status *status)
 {
 	struct i2c_client *client = fe->demodulator_priv;
@@ -180,6 +185,9 @@ static int si2168_read_status(struct dvb_frontend *fe, enum fe_status *status)
 		if (ret)
 			goto err;
 
+		if (!carrier_locked(&cmd))
+			goto parse_response;
+
 		if ((cmd.args[3] & 0x0f) == 7)
 			sys = SYS_DVBT2;
 	}
@@ -206,27 +214,10 @@ static int si2168_read_status(struct dvb_frontend *fe, enum fe_status *status)
 	}
 
 	ret = si2168_cmd_execute(client, &cmd);
-	if (dvbt_auto_plp && (ret == -EREMOTEIO)) {
-		/* In auto-PLP mode it is possible to read 0x8701 while
-		 * the frontend is in switchover transition. This causes
-		 * a status read failure, due to incorrect system. Check
-		 * the other sys if we hit this race condition.
-		 */
-		if (sys == SYS_DVBT) {
-			memcpy(cmd.args, "\x50\x01", 2); /* DVB-T2 */
-			cmd.wlen = 2;
-			cmd.rlen = 14;
-			ret = si2168_cmd_execute(client, &cmd);
-		} else if (sys == SYS_DVBT2) {
-			memcpy(cmd.args, "\xa0\x01", 2); /* DVB-T */
-			cmd.wlen = 2;
-			cmd.rlen = 13;
-			ret = si2168_cmd_execute(client, &cmd);
-		}
-	}
 	if (ret)
 		goto err;
 
+parse_response:
 	switch ((cmd.args[2] >> 1) & 0x03) {
 	case 0x01:
 		*status = FE_HAS_SIGNAL | FE_HAS_CARRIER;