linux-kernel - Re: framebuffer corruption due to overlapping stp instructions on arm64

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Date:   Mon, 6 Aug 2018 14:22:00 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Florian Weimer <fweimer@...hat.com>,
        Andrew Pinski <pinskia@...il.com>,
        Richard Earnshaw <Richard.Earnshaw@....com>,
        Ramana Radhakrishnan <ramana.gcc@...glemail.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        GNU C Library <libc-alpha@...rceware.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Russell King <linux@...linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: framebuffer corruption due to overlapping stp instructions on arm64

On 6 August 2018 at 14:19, Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> On 6 August 2018 at 14:09, Mikulas Patocka <mpatocka@...hat.com> wrote:
>>
>>
>> On Mon, 6 Aug 2018, Ard Biesheuvel wrote:
>>
>>> >> Are we talking about a quirk for the Armada 8040 or about PCIe on ARM
>>> >> in general?
>>> >
>>> > I don't know - there are not any other easily available PCIe ARM boards
>>> > except for Armada 8040.
>>>
>>> ... indeed, and sadly, the ones that are available all have this
>>> horrible Synopsys DesignWare PCIe IP that does not implement a true
>>> root complex at all, but is simply repurposed endpoint IP with some
>>> tweaks so it vaguely resembles a root complex.
>>>
>>> But this is exactly why I am asking: I use a AMD Seattle Overdrive as
>>> my main Linux development system, and it runs the gnome-shell stack
>>> flawlessly (using the nouveau driver), as well as a UEFI framebuffer
>>> using efifb. So my suspicion is that this is either a Synopsys IP
>>> issue or an interconnect issue, and has nothing to do with the
>>> impedance mismatch between AMBA and PCIe.
>>
>> If you run the program for testing memcpy on framebuffer that I posted in
>> this thread - does it detect some corruption for you?
>>
>
> I won't be able to check that for a while - I'm currently travelling.
>
>>
>> BTW. does the Radeon GPU driver work for you?
>>
>> My observation is that OpenGL with Nouveau works, but it's slow and the
>> whole system locks up when playing video in chromium.
>>

Are you setting the pstate to auto? That helps a lot in my experience.

I.e.,

echo auto > /sys/kernel/debug/dri/0/pstate