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From:   Tom Psyborg <pozega.tomislav@gmail.com>
Date:   Mon, 14 Jan 2019 10:22:09 +0100
Message-ID: <CAKR_QV+L083Lsjh4M_9+KuPBVgPKaivpmb7P5uFcGAV3fMrwvQ@mail.gmail.com>
Subject: Re: MT76x2U crashes XHCI driver on AMD Ryzen system
To:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc:     Rosen Penev <rosenp@gmail.com>,
        linux-wireless <linux-wireless@vger.kernel.org>
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On 14/01/2019, 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
>
> Regards,
> Lorenzo
>

updating grub, not reinstalling