linux-kernel - Re: [PATCH v1 2/2] usb: dwc3: Force full reset on xhci removal

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Message-ID: <CA+zupgwRNNsZumGduPf-s0eCSGzaFvTGVuuzWY1aXOBa3OxRFQ@mail.gmail.com>
Date: Thu, 15 May 2025 11:57:00 -0700
From: Roy Luo <royluo@...gle.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Thinh.Nguyen@...opsys.com, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] usb: dwc3: Force full reset on xhci removal

On Thu, May 15, 2025 at 12:34 AM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Thu, May 15, 2025 at 04:02:59AM +0000, Roy Luo wrote:
> > During an xhci host controller reset (via `USBCMD.HCRST`), reading DWC3
> > registers can return zero instead of their actual values. This applies
> > not only to registers within the xhci memory space but also those in
> > the broader DWC3 IP block.
> >
> > By default, the xhci driver doesn't wait for the reset handshake to
> > complete during teardown. This can cause problems when the DWC3 controller
> > is operating as a dual role device and is switching from host to device
> > mode, the invalid register read caused by ongoing HCRST could lead to
> > gadget mode startup failures and unintended register overwrites.
> >
> > To mitigate this, enable xhci-full-reset-on-remove-quirk to ensure that
> > xhci_reset() completes its full reset handshake during xhci removal.
> >
> > Signed-off-by: Roy Luo <royluo@...gle.com>
> > ---
> >  drivers/usb/dwc3/host.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
>
> What commit id does this fix?  Should it also go to stable kernels?  If
> so, how far back?
>
> thanks,
>
> greg k-h

Added Fixes tag and cc stable in v2.

Thanks,
Roy