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

[Programmingkid]

> 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.