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From:   Puma Hsu <pumahsu@google.com>
Date:   Wed, 29 Dec 2021 13:53:04 +0800
Message-ID: <CAGCq0Lb8ZoGpbkLNhXG=OyWgvz_Qn3ABmq_uvMPJdyEKygMH+Q@mail.gmail.com>
Subject: Re: [PATCH] xhci: re-initialize the HC during resume if HCE was set
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     mathias.nyman@intel.com, Albert Wang <albertccwang@google.com>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
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This commit is not used to fix a specific commit. We find a condition
that when XHCI runs the resume process but the HCE flag is set, then
the Run/Stop bit of USBCMD cannot be set so that HC would not be
enabled. In fact, HC may already meet a problem at this moment.
Besides, in xHCI requirements specification revision 1.2, Table 5-21
BIT(12) claims that Software should re-initialize the xHC when HCE is
set. Therefore, I think this commit could be the error handling for
HCE.

Thanks in advance.


Thanks in advance.


  =E2=80=A2  Puma Hsu =E8=A8=B1=E8=AA=8C=E5=AE=8F
  =E2=80=A2  Software Engineer, Pixel Phone
  =E2=80=A2  Tel: +886 2 8729 0870
  =E2=80=A2  pumahsu@google.com


On Tue, Dec 28, 2021 at 4:26 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Dec 28, 2021 at 02:02:46PM +0800, Puma Hsu wrote:
> > When HCE(Host Controller Error) is set, it means an internal
> > error condition has been detected. It needs to re-initialize
> > the HC too.
> >
> > Signed-off-by: Puma Hsu <pumahsu@google.com>
> > ---
> >  drivers/usb/host/xhci.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index dc357cabb265..c546d9533410 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -1146,8 +1146,8 @@ int xhci_resume(struct xhci_hcd *xhci, bool hiber=
nated)
> >               temp =3D readl(&xhci->op_regs->status);
> >       }
> >
> > -     /* If restore operation fails, re-initialize the HC during resume=
 */
> > -     if ((temp & STS_SRE) || hibernated) {
> > +     /* If restore operation fails or HC error is detected, re-initial=
ize the HC during resume */
> > +     if ((temp & STS_SRE) || (temp & STS_HCE) || hibernated) {
> >
> >               if ((xhci->quirks & XHCI_COMP_MODE_QUIRK) &&
> >                               !(xhci_all_ports_seen_u0(xhci))) {
> > --
> > 2.34.1.448.ga2b2bfdf31-goog
> >
>
> What commit does this fix?  Does it need to be backported to older
> kernels as well?
>
> thanks,
>
> greg k-h