[media] m88ds3103: calculate DiSEqC message sending time

DiSEqC message sending takes 13.5 ms per byte, which is 54 ms total
when typical 4 byte message is sent. Don't hard-code time limit to
54 ms, but calculate it. Time limit is only used to determine when to
start poll "DiSEqC Tx ready" status from the chip.
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/dvb-frontends/m88ds3103.c

@@ -1116,8 +1116,9 @@ static int m88ds3103_diseqc_send_master_cmd(struct dvb_frontend *fe,
 	#define SEND_MASTER_CMD_TIMEOUT 120
 	timeout = jiffies + msecs_to_jiffies(SEND_MASTER_CMD_TIMEOUT);
 
-	/* DiSEqC message typical period is 54 ms */
-	usleep_range(50000, 54000);
+	/* DiSEqC message period is 13.5 ms per byte */
+	utmp = diseqc_cmd->msg_len * 13500;
+	usleep_range(utmp - 4000, utmp);
 
 	for (utmp = 1; !time_after(jiffies, timeout) && utmp;) {
 		ret = regmap_read(dev->regmap, 0xa1, &utmp);