On Mon, May 31, 2021 at 11:22 PM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
> On Mon, May 31, 2021 at 6:45 PM Andy Shevchenko
> <andy.shevchenko@xxxxxxxxx> wrote:
> >
> > On Mon, May 31, 2021 at 5:49 PM Greg Kroah-Hartman
> > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > On Mon, May 31, 2021 at 05:33:02PM +0300, Andy Shevchenko wrote:
> > > > Hi!
> > > >
> > > > The only patch that made v5.13-rc4 effectively broke USB on Intel Merrifield.
> > > >
> > > > My reproducer:
> > > > 1. Boot with switch in gadget mode
> > > > 2. Enable USB ethernet
> > > > 3. Switch to host
> > > > 4. wait a bit for device enumeration, etc
> > > > 5. Switch back
> > > > 6. No gadget mode, kernel RCU stall detected (USB become unusable, so
> > > > does the system)
> > > >
> > > > [ 115.792620] rcu: INFO: rcu_sched self-detected stall on CPU
> > > > [ 115.798410] rcu: 0-....: (24089 ticks this GP)
> > > > idle=886/1/0x4000000000000000 softirq=3796/3797 fqs=5240
> > > > [ 115.808333] (t=21000 jiffies g=6505 q=12158)
> > > > [ 115.812847] NMI backtrace for cpu 0
> > > > [ 115.816472] CPU: 0 PID: 23 Comm: kworker/0:1 Not tainted 5.13.0-rc4+ #213
> > > > ...
> > > >
> > > > [ 115.977913] add_dma_entry+0xd4/0x1d0
> > > > [ 115.981760] dma_map_page_attrs+0xd8/0x220
> > > > [ 115.986063] usb_hcd_map_urb_for_dma+0x3b6/0x4f0
> > > > [ 115.990895] usb_hcd_submit_urb+0x98/0xbf0
> > > > [ 115.995263] dln2_rx+0x1ae/0x280 [dln2]
> > > > ...
> > > >
> > > > 100% Reproducibility, revert of the 25dda9fc56bd ("usb: dwc3: gadget:
> > > > Properly track pending and queued SG") fixes the issue.
> > > >
> > > > Please, fix it properly or revert. Thanks!
> > >
> > > Care to send the revert?
> >
> > Sure, But I want to give Thinh a chance to react to this, maybe it
> > would be a better idea.
> > Let's say if nothing happens I will send it on Wednesday.
>
> Please, hold on, I have to perform additional testing (something odd
> is going on on my side).
It appears that the reported patch has nothing to do with the issue.
It "luckily" helped, but under more tests I managed to dive as deep as
v5.11 and got the same issue. I will continue investigating and will
inform / send patch / etc when I find more robust reproducer. Anyway
it's not the reported patch for sure, sorry for the noise.
(It seems I'm looking in a wrong corner< I have some ideas, but it
requires time to check)
--
With Best Regards,
Andy Shevchenko
