From 4fb65ae3e84f536a9b924082b7c59a30d5802e6b Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Sun, 21 Jun 2020 21:36:50 +0200
Subject: [PATCH] devusb: keep isochronous ep->hz consistent with maxpkt, ntds
 and pollival

The sample frequency is an artificial parameter used for
isochronous out transfers to better match the target
frequency (usually, a sound card).

when hz is set, devusb adjusts the endpoint's maxpkt to get
the requested frequency and a multiple of the samplesize per
packet.

however, when hz is not set, then we should calculate the
frequency from maxpkt, ntds and pollival, so all parameters
will be consistent with each other.
---
 sys/src/9/port/devusb.c | 104 ++++++++++++++++++++++++----------------
 1 file changed, 62 insertions(+), 42 deletions(-)

diff --git a/sys/src/9/port/devusb.c b/sys/src/9/port/devusb.c
index 4d439b46d..e395df265 100644
--- a/sys/src/9/port/devusb.c
+++ b/sys/src/9/port/devusb.c
@@ -525,8 +525,8 @@ newdevep(Ep *ep, int i, int tt, int mode)
 	case Tiso:
 		nep->tmout = Xfertmout;
 		nep->pollival = 10;
-		nep->samplesz = 4;
-		nep->hz = 44100;
+		nep->samplesz = 1;
+		nep->hz = 0;
 		nep->uframes = 0;
 		break;
 	}
@@ -859,6 +859,58 @@ usbload(int speed, int maxpkt)
 	return l / 1000UL;	/* in µs */
 }
 
+static void
+isotiming(Ep *ep)
+{
+	long spp, max;
+
+	switch(ep->dev->speed){
+	case Fullspeed:
+		max = 1024;
+		break;
+	case Highspeed:
+		max = 3*1024;
+		break;
+	case Superspeed:
+		max = 48*1024;
+		break;
+	default:
+		error(Egreg);
+		return;
+	}
+
+	if(ep->ntds <= 0)
+		error(Egreg);
+	max /= ep->ntds;
+	if(max < ep->samplesz)
+		error(Egreg);
+	if(ep->pollival <= 0)
+		error(Egreg);
+
+	if(ep->hz <= 0){
+		spp = ep->maxpkt / ep->samplesz;
+		spp *= ep->ntds;
+		if(ep->dev->speed == Fullspeed || ep->dev->speed == Lowspeed)
+			ep->hz = (1000 * spp) / ep->pollival;
+		else
+			ep->hz = (8000 * spp) / ep->pollival;
+		if(ep->hz <= 0)
+			error(Egreg);
+	}
+	if(ep->dev->speed == Fullspeed || ep->dev->speed == Lowspeed)
+		spp = (ep->hz * ep->pollival + 999) / 1000;
+	else
+		spp = (ep->hz * ep->pollival + 7999) / 8000;
+	spp /= ep->ntds;
+	ep->maxpkt = spp * ep->samplesz;
+	if(ep->maxpkt > max){
+		print("ep%d.%d: maxpkt %ld > %ld for %s, truncating\n",
+			ep->dev->nb, ep->nb,
+			ep->maxpkt, max, spname[ep->dev->speed]);
+		ep->maxpkt = max;
+	}
+}
+
 static Chan*
 usbopen(Chan *c, int omode)
 {
@@ -901,6 +953,9 @@ usbopen(Chan *c, int omode)
 		error(Enotconf);
 	ep->clrhalt = 0;
 	ep->rhrepl = -1;
+
+	if(ep->ttype == Tiso)
+		isotiming(ep);
 	if(ep->load == 0 && ep->dev->speed != Superspeed)
 		ep->load = usbload(ep->dev->speed, ep->maxpkt);
 	ep->hp->epopen(ep);
@@ -1159,40 +1214,6 @@ usbread(Chan *c, void *a, long n, vlong offset)
 	return n;
 }
 
-static void
-setmaxpkt(Ep *ep, char* s)
-{
-	long spp, max;	/* samples per packet */
-
-	if(ep->dev->speed == Fullspeed)
-		spp = (ep->hz * ep->pollival + 999) / 1000;
-	else
-		spp = (ep->hz * ep->pollival * ep->ntds + 7999) / 8000;
-	ep->maxpkt = spp * ep->samplesz;
-	deprint("usb: %s: setmaxpkt: hz %ld poll %ld"
-		" ntds %d %s speed -> spp %ld maxpkt %ld\n", s,
-		ep->hz, ep->pollival, ep->ntds, spname[ep->dev->speed],
-		spp, ep->maxpkt);
-	switch(ep->dev->speed){
-	case Fullspeed:
-		max = 1024;
-		break;
-	case Highspeed:
-		max = 3*1024;
-		break;
-	case Superspeed:
-		max = 48*1024;
-		break;
-	default:
-		return;
-	}
-	if(ep->maxpkt*ep->ntds > max){
-		print("usb: %s: maxpkt %ld > %ld for %s, truncating\n",
-			s, ep->maxpkt*ep->ntds, max, spname[ep->dev->speed]);
-		ep->maxpkt = max/ep->ntds;
-	}
-}
-
 /*
  * Many endpoint ctls. simply update the portable representation
  * of the endpoint. The actual controller driver will look
@@ -1287,6 +1308,7 @@ epctl(Ep *ep, Chan *c, void *a, long n)
 			error("maxpkt not in [1:1024]");
 		qlock(ep);
 		ep->maxpkt = l;
+		ep->hz = 0; /* recalculate */
 		qunlock(ep);
 		break;
 	case CMntds:
@@ -1296,6 +1318,7 @@ epctl(Ep *ep, Chan *c, void *a, long n)
 			error("ntds not in [1:3]");
 		qlock(ep);
 		ep->ntds = l;
+		ep->hz = 0; /* recalculate */
 		qunlock(ep);
 		break;
 	case CMpollival:
@@ -1313,8 +1336,7 @@ epctl(Ep *ep, Chan *c, void *a, long n)
 		}
 		qlock(ep);
 		ep->pollival = l;
-		if(ep->ttype == Tiso)
-			setmaxpkt(ep, "pollival");
+		ep->hz = 0; /* recalculate */
 		qunlock(ep);
 		break;
 	case CMsamplesz:
@@ -1326,7 +1348,6 @@ epctl(Ep *ep, Chan *c, void *a, long n)
 			error("samplesz not in [1:8]");
 		qlock(ep);
 		ep->samplesz = l;
-		setmaxpkt(ep, "samplesz");
 		qunlock(ep);
 		break;
 	case CMhz:
@@ -1334,11 +1355,10 @@ epctl(Ep *ep, Chan *c, void *a, long n)
 			error("not an iso endpoint");
 		l = strtoul(cb->f[1], nil, 0);
 		deprint("usb epctl %s %d\n", cb->f[0], l);
-		if(l <= 0 || l > 100000)
-			error("hz not in [1:100000]");
+		if(l <= 0 || l > 1000000000)
+			error("hz not in [1:1000000000]");
 		qlock(ep);
 		ep->hz = l;
-		setmaxpkt(ep, "hz");
 		qunlock(ep);
 		break;
 	case CMuframes: