Re: mceusb xhci issue?

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On Sat, 9 Jul 2016, Mauro Carvalho Chehab wrote:

> C/C linux-usb Mailing list:
> 
> 
> Em Wed, 18 May 2016 08:52:28 -0600
> Wade Berrier <wberrier@xxxxxxxxx> escreveu:

...

> > > That message above links to some other threads describing the issue.
> > > Here's a post with a patch that supposedly works:
> > > 
> > > http://www.gossamer-threads.com/lists/mythtv/users/587930
> > > 
> > > No idea if that's the "correct" way to fix this.
> > > 
> > > I'll be trying that out and then report back...  
> > 
> > Indeed, this patch does fix the issue:
> > 
> > ----------------------
> > 
> > diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> > index 31ccdcc..03321d4 100644
> > --- a/drivers/usb/core/config.c
> > +++ b/drivers/usb/core/config.c
> > @@ -247,7 +247,7 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
> >  			/* For low-speed, 10 ms is the official minimum.
> >  			 * But some "overclocked" devices might want faster
> >  			 * polling so we'll allow it. */
> > -			n = 32;
> > +			n = 10;
> >  			break;
> >  		}
> >  	} else if (usb_endpoint_xfer_isoc(d)) {
> > 
> > 
> > ----------------------
> > 
> > Is this change appropriate to be pushed upstream?  Where to go from
> > here?
> 
> This issue is at the USB core. So, it should be reported to the
> linux-usb mailing list. 
> 
> The people there should help about how to proceed to get this
> fixed upstream.

Here's a proper version of that patch.  If this is okay, it can be 
merged.

Alan Stern



Index: usb-4.x/drivers/usb/core/config.c
===================================================================
--- usb-4.x.orig/drivers/usb/core/config.c
+++ usb-4.x/drivers/usb/core/config.c
@@ -213,8 +213,10 @@ static int usb_parse_endpoint(struct dev
 	memcpy(&endpoint->desc, d, n);
 	INIT_LIST_HEAD(&endpoint->urb_list);
 
-	/* Fix up bInterval values outside the legal range. Use 32 ms if no
-	 * proper value can be guessed. */
+	/*
+	 * Fix up bInterval values outside the legal range.
+	 * Use 10 or 8 ms if no proper value can be guessed.
+	 */
 	i = 0;		/* i = min, j = max, n = default */
 	j = 255;
 	if (usb_endpoint_xfer_int(d)) {
@@ -223,13 +225,15 @@ static int usb_parse_endpoint(struct dev
 		case USB_SPEED_SUPER_PLUS:
 		case USB_SPEED_SUPER:
 		case USB_SPEED_HIGH:
-			/* Many device manufacturers are using full-speed
+			/*
+			 * Many device manufacturers are using full-speed
 			 * bInterval values in high-speed interrupt endpoint
 			 * descriptors. Try to fix those and fall back to a
-			 * 32 ms default value otherwise. */
+			 * 8 ms default value otherwise.
+			 */
 			n = fls(d->bInterval*8);
 			if (n == 0)
-				n = 9;	/* 32 ms = 2^(9-1) uframes */
+				n = 7;	/* 8 ms = 2^(7-1) uframes */
 			j = 16;
 
 			/*
@@ -247,7 +251,7 @@ static int usb_parse_endpoint(struct dev
 			/* For low-speed, 10 ms is the official minimum.
 			 * But some "overclocked" devices might want faster
 			 * polling so we'll allow it. */
-			n = 32;
+			n = 10;
 			break;
 		}
 	} else if (usb_endpoint_xfer_isoc(d)) {
@@ -255,10 +259,10 @@ static int usb_parse_endpoint(struct dev
 		j = 16;
 		switch (to_usb_device(ddev)->speed) {
 		case USB_SPEED_HIGH:
-			n = 9;		/* 32 ms = 2^(9-1) uframes */
+			n = 7;		/* 8 ms = 2^(7-1) uframes */
 			break;
 		default:		/* USB_SPEED_FULL */
-			n = 6;		/* 32 ms = 2^(6-1) frames */
+			n = 4;		/* 8 ms = 2^(4-1) frames */
 			break;
 		}
 	}

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