Re: [PATCH 1/2] usb: pci-quirks: Correct AMD PLL quirk detection

From: Ryan Kennedy <ryan5544@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: mathias.nyman@intel.com, stern@rowland.harvard.edu,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] usb: pci-quirks: Correct AMD PLL quirk detection
Date: Fri, 5 Jul 2019 10:48:13 -0400	[thread overview]
Message-ID: <CAJRN7XN0rKVsLtfOTeEt7JN69pdOtPkV31iAnN3fLiyYtejcQw@mail.gmail.com> (raw)
In-Reply-To: <20190705052208.GE15821@kroah.com>

On Fri, Jul 5, 2019 at 1:22 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Thu, Jul 04, 2019 at 11:35:28AM -0400, Ryan Kennedy wrote:
> > The AMD PLL USB quirk is incorrectly enabled on newer Ryzen
> > chipsets. The logic in usb_amd_find_chipset_info currently checks
> > for unaffected chipsets rather than affected ones. This broke
> > once a new chipset was added in e788787ef. It makes more sense
> > to reverse the logic so it won't need to be updated as new
> > chipsets are added. Note that the core of the workaround in
> > usb_amd_quirk_pll does correctly check the chipset.
> >
> > Signed-off-by: Ryan Kennedy <ryan5544@gmail.com>
> > ---
> >  drivers/usb/host/pci-quirks.c | 31 +++++++++++++++++++------------
> >  1 file changed, 19 insertions(+), 12 deletions(-)
>
> Should this be backported to stable kernels?

The bug is fairly harmless, so I wouldn't say it's a must-have. I only
noticed this because I saw the log message and was curious what the
quirk was for. The fix saves us calling usb_amd_quirk_pll() and taking
the lock in there. Others here should know better than I what's stable
worthy.

Ryan

>
> thanks,
>
> greg k-h