Re: [PATCH v2] USB: Disable USB2 LPM at shutdown

Greg KH
2019-08-05T13:26:23Z

On Mon, Aug 05, 2019 at 08:58:33PM +0800, Kai-Heng Feng wrote:
> Hi Greg,
>
> at 17:22, Kai-Heng Feng <kai.heng.feng@canonical.com> wrote:
>
> > at 22:17, Alan Stern <stern@rowland.harvard.edu> wrote:
> > >
> > > I agree with Kai-Heng, this seems like a fairly light-weight solution
> > > to a reasonable problem.
> >
> > Thanks for your review.
> >
> > > As to the issue of how much it will slow down system shutdowns, I have
> > > no idea. Probably not very much, unless somebody has an unusually
> > > large number of USB devices plugged in, but only testing can give a
> > > real answer.
> >
> > In addition to that, only USB2 devices that enable LPM will slow down
> > shutdown process.
> > Right now only internally connected USB2 devices enable LPM, so the
> > numbers are even lower.
> >
> > > I suppose we could add an HCD flag for host controllers which require
> > > this workaround. Either way, it's probably not a very big deal.
> >
> > IMO this is not necessary. Only xHCI that reports hw_lpm_support will be
> > affected. At least for PC, this only became true after Whiskey Lake.
> >
> > Kai-Heng
> >
> > > Alan Stern
>
> This patch is included in Ubuntu’s kernel for a while now, and there’s no
> regression report so far.
> Please consider merge this patch.

I do not see a patch here at all, sorry. Please resend it.

greg k-h