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From:   Rosen Penev <rosenp@gmail.com>
Date:   Mon, 14 Jan 2019 12:06:12 -0800
Message-ID: <CAKxU2N8ioMszBCyQcH7CVhgBdW4aj7yZ+kYQe14DCV5OSAnxrg@mail.gmail.com>
Subject: Re: MT76x2U crashes XHCI driver on AMD Ryzen system
To:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>
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Sender: linux-wireless-owner@vger.kernel.org
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On Mon, Jan 14, 2019 at 1:18 AM Lorenzo Bianconi
<lorenzo.bianconi@redhat.com> wrote:
>
> > On Sun, Jan 13, 2019 at 11:00 AM Lorenzo Bianconi
> > <lorenzo.bianconi@redhat.com> wrote:
> > >
> > > >
> > > >
> > > > On Sun, Jan 13, 2019 at 5:33 AM, Lorenzo Bianconi <lorenzo.bianconi@redhat.com> wrote:
> > > >
> > > > Direct. No VM used. This is the only peripheral causing this issue.
> > > >
> > > > Is the device connected to a usb3.0 port? If so, could you please try to connect the dongle to a 2.0 one?
> > > >
> > > > I tried through a USB 2.0 port. Shouldn't make a difference as they both use the xhci driver.
> > > >
> > >
> > > mt76x2u supports scatter-gather on usb 3.0 (not on 2.0)
> > Tried a USB 3 port. Same result.
> > >
> > > > Could you please double check if IOMMU is enabled?
> > > >
> > >
> > > Have you tried to disable it? Does it make any difference?
> > No idea how. UEFI doesn't seem to show anything similar.
> >
> > Similar bug report: https://bugzilla.kernel.org/show_bug.cgi?id=202241
>
> You should be able to disable iommu using GRUB_CMDLINE_LINUX in
> /etc/default/grub (I guess setting iommu=off and reinstalling grub)
> https://wiki.gentoo.org/wiki/IOMMU_SWIOTLB
Yep. Working great now. I wonder what mt76 is doing to cause the crash though...
>
> Regards,
> Lorenzo