Re: Implementing isochronous transfers in hw/hcd-ohci.c

[Programmingkid]

> On Sep 11, 2021, at 5:46 AM, Howard Spoelstra <hsp.cat7@gmail.com> wrote:
> 
> 
> 
> On Fri, Sep 10, 2021 at 9:23 PM Programmingkid <programmingkidx@gmail.com> 
> wrote:
> 
> 
> > On Sep 10, 2021, at 7:51 AM, BALATON Zoltan <balaton@eik.bme.hu> wrote:
> > 
> > On Fri, 10 Sep 2021, Howard Spoelstra wrote:
> >> On Fri, Sep 10, 2021 at 7:07 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
> >> 
> >>> On Thu, Sep 09, 2021 at 05:06:17PM -0400, Programmingkid wrote:
> >>>> Hi Gerd,
> >>>> 
> >>>> Howard and I were talking about USB audio problems with Mac OS guests.
> >>> We think the issue might be with frames being sent to the USB audio card
> >>> too soon. My guess is only one frame is suppose to be transmitted every 1
> >>> millisecond. I was also reading the todo notes in the file hw/hcd-ohci.c.
> >>> This is what it says:
> >>>> 
> >>>> * TODO:
> >>>> *  o Isochronous transfers
> >>>> *  o Allocate bandwidth in frames properly
> >>>> *  o Disable timers when nothing needs to be done, or remove timer usage
> >>>> *    all together.
> >>>> *  o BIOS work to boot from USB storage
> >>>> */
> >>>> 
> >>>> Do you think implementing isochronous transfers would fix the audio
> >>> problems Mac OS guest are experiencing?
> >>> 
> >>> Most likely yes, audio devices typically use iso endpints.
> >>> 
> >>> take care,
> >>>  Gerd
> >>> 
> >> 
> >> Hi,
> >> 
> >> Below I pasted the first lines mentioning isochronous traffic from a pcap
> >> file when running fedora12 with the usb-audio device and the first lines
> >> from a pcap file running Mac OS 9.2 with the usb-audio device
> >> 
> >> Fedora:
> >> 91 56.715001 host 0.5.1 USB 256 URB_ISOCHRONOUS out
> >> 92 56.715018 0.5.1 host USB 64 URB_ISOCHRONOUS out
> >> 
> >> MacOS:
> >> 143 56.031989 host 0.16.1 USB 256 URB_ISOCHRONOUS out
> >> 144 56.032026 0.16.1 host USB 64 URB_ISOCHRONOUS out
> >> 
> >> The usb-audio device works for the fedora guest, so would this not indicate
> >> that the iso endpoints are already working?
> >> 
> >> The usb-audio device also work (for a limited amount of time) when running
> >> MacOS. Looking at USB logging in the Mac OS guest, to me it seems the MacOS
> >> side runs into timing issues when packages drift too far apart. It then
> >> finally gives up trying to keep the stream open.
> > 
> > I was also trying to find why the usb-audio device does not work with 
> > MorphOS but I could not figure it out. Now I have two machines (mac99 and 
> > pegasos2) that can boot MorphOS but usb-audio does not work with either so 
> > maybe it's not because of the USB controller. I've found there is a debug 
> > property that enables some logging: -device usb-audio,debug=1 but that did 
> > not reveal much more. It looks like MorphOS tries to query the device but 
> > replies come very slow (not sure if that's normal or a problem) then just 
> > gives up after a while. Maybe you can try comparing what Fedora and other 
> > OSes query as it may be we're missing some info in USB descriptors that 
> > other drivers than Linux's rely on but that's just a guess I haven't tested 
> > with Linux guest on pegasos2 or mac99 yet.
> > 
> > Regards,
> > BALATON Zoltan
> 
> Thank for the info everyone. When I try to use the USB-Audio device in Mac OS 
> 10.4.11, the operating system doesn't use it. It does show up in the System 
> Profiler application. In Mac OS 9.2 the sound from it is perfect sounding, 
> but the operating system crashes after less than a minute. In Mac OS 10.2.3 
> the operating system does set it as its output device but it does not work.
> 
> To find out what is wrong we would probably have to build the USB audio 
> drivers in Mac OS X and enable debug output to see what is wrong. They are 
> open source and I have done this in the past. As for Mac OS 9, I'm not sure 
> how to debug its driver.
> 
> See the screen shot attached for the warnings about timing in MacOS 9.2 
> before the stream collapses.This was after some system sounds were played 
> successfully.
> <usb-audiolog.png>
> Best,
> Howard

So the question to answer is what is the wr gap?