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Date:   Mon, 6 Aug 2018 08:09:50 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@redhat.com>
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc:     Florian Weimer <fweimer@redhat.com>,
        Andrew Pinski <pinskia@gmail.com>,
        Richard Earnshaw <Richard.Earnshaw@arm.com>,
        Ramana Radhakrishnan <ramana.gcc@googlemail.com>,
        Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
        GNU C Library <libc-alpha@sourceware.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Russell King <linux@armlinux.org.uk>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: framebuffer corruption due to overlapping stp instructions on
 arm64
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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?


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.

Radeon HD 6350 (pre-GCN), doesn't lock up, but OpenGL (and Glamour) has 
many artifacts and corrupted textures. When I switch it to EXA 
acceleration and don't use OpenGL, it works.

The artifacts are not fixed by preloading a glibc with fixed memcpy, so 
there's supposedly some other bug somewhere.


Unfortunatelly, there's no low-power GCN card.

Mikulas