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

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Message-ID: <20190805130621.GA25026@kroah.com>
Date:   Mon, 5 Aug 2019 15:06:21 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Linux USB List <linux-usb@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] USB: Disable USB2 LPM at shutdown

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@...onical.com> wrote:
> 
> > at 22:17, Alan Stern <stern@...land.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