Re: [RFC PATCH 01/12] drivers/char: Add support for Xue USB3 debugger

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Mon, Jun 06, 2022 at 12:57:26PM -0400, Tamas K Lengyel wrote:
> On Mon, Jun 6, 2022 at 10:10 AM Tamas K Lengyel
> <tamas.k.lengyel@gmail.com> wrote:
> >
> > On Mon, Jun 6, 2022 at 10:03 AM Marek Marczykowski-Górecki
> > <marmarek@invisiblethingslab.com> wrote:
> > >
> > > On Mon, Jun 06, 2022 at 09:32:52AM -0400, Tamas K Lengyel wrote:
> > > > > +/* Supported xHC PCI configurations */
> > > > > +#define XUE_XHC_CLASSC 0xC0330ULL
> > > > > +#define XUE_XHC_VEN_INTEL 0x8086ULL
> > > > > +#define XUE_XHC_DEV_Z370 0xA2AFULL
> > > > > +#define XUE_XHC_DEV_Z390 0xA36DULL
> > > > > +#define XUE_XHC_DEV_WILDCAT_POINT 0x9CB1ULL
> > > > > +#define XUE_XHC_DEV_SUNRISE_POINT 0x9D2FULL
> > > > > +#define XUE_XHC_DEV_CANNON_POINT 0x9DEDULL
> > > >
> > > > I had to add an extra device ID here to get it working on my NUC,
> > > > would be nice if we could add that to the list of supported configs so
> > > > I don't need to custom patch:
> > > >
> > > > #define XUE_XHC_DEV_COMET_LAKE 0x02EDULL
> > > >
> > > > The patch is here:
> > > > https://github.com/tklengyel/xen/commit/dd0423aba6caa4ef41dff65470598a1c0c1105ae
> > >
> > > Interesting, I think known_xhc() is used only in the EFI variant of Xue.
> > > Xen one just looks for any XHC based on the device class. And indeed, I
> > > works for me on Tiger Lake that is not included here.
> > >
> > > I did need to select specific controller, since I have 3 of them:
> > > 00:0d.0 USB controller: Intel Corporation Tiger Lake-LP Thunderbolt 4 USB Controller (rev 01)
> > > 00:0d.2 USB controller: Intel Corporation Tiger Lake-LP Thunderbolt 4 NHI #0 (rev 01)
> > > 00:14.0 USB controller: Intel Corporation Tiger Lake-LP USB 3.2 Gen 2x1 xHCI Host Controller (rev 20)
> > >
> > > So, I need dbgp=xue2 or dbgp=xue@pci00:14.0.
> >
> > Interesting! OK, I'll give that a shot and see if it works that way
> > for me too, it's certainly been a while since I last tested :)
> 
> Yeap, with console=dbgp dbgp=xue@pci00:14.0 it works as expected.
> Xen's boot does hang if you don't have a debug cable connected or if
> the other end is not plugged into the right USB3 port. Not sure if
> that behavior is documented anywhere. Once I found the right USB3 port
> on the machine that receives the debug output it started booting and
> everything works expected (ie. one-way communication only).

Indeed, the indefinite wait for the connection is not the most
convenient. For debugging, I added some timeout, but it was based on
the loop iterations not an actual time (not sure if there is any time
source available at this early stage...). I'll see if this can be
improved.

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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