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From: Marcin Wojtas <mw@semihalf.com>
To: mpatocka@redhat.com
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Joao Pinto <Joao.Pinto@synopsys.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-pci@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Matt Sealey <neko@bakuhatsu.net>,
	Jingoo Han <jingoohan1@gmail.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: framebuffer corruption due to overlapping stp instructions on arm64
Date: Mon, 6 Aug 2018 15:41:34 +0200	[thread overview]
Message-ID: <CAPv3WKdxwoW5MAOvy6uEBEuMpsigMo98hyO+TpKMsFrKR9oBzg@mail.gmail.com> (raw)
In-Reply-To: <99fff4fe-afa9-f12f-a518-472a9dd1c530@arm.com>

Hi Mikulas,

pon., 6 sie 2018 o 14:42 Robin Murphy <robin.murphy@arm.com> napisał(a):
>
> On 06/08/18 11:25, Mikulas Patocka wrote:
> [...]
> >> None of this explains why some transactions fail to make it across
> >> entirely. The overlapping writes in question write the same data to
> >> the memory locations that are covered by both, and so the ordering in
> >> which the transactions are received should not affect the outcome.
> >
> > You're right that the corruption couldn't be explained just by reordering
> > writes. My hypothesis is that the PCIe controller tries to disambiguate
> > the overlapping writes, but the disambiguation logic was not tested and it
> > is buggy. If there's a barrier between the overlapping writes, the PCIe
> > controller won't see any overlapping writes, so it won't trigger the
> > faulty disambiguation logic and it works.
> >
> > Could the ARM engineers look if there's some chicken bit in Cortex-A72
> > that could insert barriers between non-cached writes automatically?
>
> I don't think there is, and even if there was I imagine it would have a
> pretty hideous effect on non-coherent DMA buffers and the various other
> places in which we have Normal-NC mappings of actual system RAM.
>
> > I observe these kinds of corruptions:
> > - failing to write a few bytes
>
> That could potentially be explained by the reordering/atomicity issues
> Matt mentioned, i.e. the load is observing part of the store, before the
> store has fully completed.
>
> > - writing a few bytes that were written 16 bytes before
> > - writing a few bytes that were written 16 bytes after
>
> Those sound more like the interconnect or root complex ignoring the byte
> strobes on an unaligned burst, of which I think the simplistic view
> would be "it's broken".
>
> FWIW I stuck my old Nvidia 7600GT card in my Arm Juno r2 board (2x
> Cortex-A72), built your test program natively with GCC 8.1.1 at -O2, and
> it's still happily flickering pixels in the corner of the console after
> nearly an hour (in parallel with some iperf3 just to ensure plenty of
> PCIe traffic). I would strongly suspect this issue is particular to
> Armada 8k, so its' probably one for the Marvell folks to take a closer
> look at - I believe some previous interconnect issues on those SoCs were
> actually fixable in firmware.
>
>

On my Macchiato I use GT630 card (nuveau driver) + debian + xfce
desktop and in dual monitor mode, I could run a couple of 1080p
streams. All smooth and I've never noticed any image corruption
whatsoever (I spent a lot of time in front of such setup). Just to be
on a safe side, can you send me a bootlog and your board revision? I'd
like to see your firware version and type.

Thanks,
Marcin

  parent reply	other threads:[~2018-08-06 13:41 UTC|newest]

Thread overview: 95+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-02 19:31 framebuffer corruption due to overlapping stp instructions on arm64 Mikulas Patocka
     [not found] ` <CAHCPf3tFGqkYEcWNN4LaWThw_rVqT316pzLv6T7RfxwO-eZ0EA@mail.gmail.com>
2018-08-03  6:35   ` Mikulas Patocka
2018-08-03  7:16     ` Ard Biesheuvel
2018-08-03  9:41       ` Will Deacon
2018-08-03 17:09         ` Mikulas Patocka
2018-08-03 17:32           ` Sinan Kaya
2018-08-03 17:33           ` Ard Biesheuvel
2018-08-03 18:25             ` Mikulas Patocka
2018-08-03 20:44               ` Matt Sealey
2018-08-03 21:20                 ` Ard Biesheuvel
2018-08-06 10:25                   ` Mikulas Patocka
2018-08-06 12:42                     ` Robin Murphy
2018-08-06 12:53                       ` Ard Biesheuvel
2018-08-06 13:41                       ` Marcin Wojtas [this message]
2018-08-06 13:48                         ` Ard Biesheuvel
2018-08-06 14:07                           ` Marcin Wojtas
2018-08-06 14:13                             ` Mikulas Patocka
2018-08-06 15:47                       ` Ard Biesheuvel
2018-08-06 17:09                         ` Mikulas Patocka
2018-08-06 17:21                           ` Ard Biesheuvel
2018-08-06 19:54                             ` Mikulas Patocka
2018-08-06 20:11                               ` Ard Biesheuvel
2018-08-06 20:31                                 ` Mikulas Patocka
2018-08-07 16:40                                 ` Marcin Wojtas
2018-08-07 17:39                                   ` Mikulas Patocka
2018-08-07 18:07                                     ` Ard Biesheuvel
2018-08-07 18:17                                       ` Mikulas Patocka
     [not found]                                     ` <CAPv3WKcKoEe=Qysp6Oac2C=G9bUhUQf1twSRCY+_qJ6XEC-iag@mail.gmail.com>
2018-08-08 14:10                                       ` Mikulas Patocka
2018-08-06 17:13                         ` Catalin Marinas
2018-08-06 17:19                           ` Mikulas Patocka
2018-08-08 18:31                       ` Mikulas Patocka
2018-08-04 13:29                 ` Mikulas Patocka
2018-08-08 12:16                 ` Catalin Marinas
2018-08-08 13:02                   ` David Laight
2018-08-08 13:46                     ` Mikulas Patocka
2018-08-08 14:26                       ` David Laight
2018-08-08 14:50                         ` Catalin Marinas
2018-08-08 16:21                           ` Mikulas Patocka
2018-08-08 16:31                             ` Arnd Bergmann
2018-08-08 16:43                               ` David Laight
2018-08-08 18:56                                 ` Mikulas Patocka
2018-08-08 18:37                         ` Mikulas Patocka
2018-08-08 11:39           ` Catalin Marinas
2018-08-08 14:12             ` Mikulas Patocka
2018-08-08 14:28               ` Catalin Marinas
2018-08-08 18:40                 ` Mikulas Patocka
2018-08-08 15:01               ` Richard Earnshaw (lists)
2018-08-08 15:14                 ` Catalin Marinas
2018-08-08 16:01                   ` Arnd Bergmann
2018-08-08 18:25                     ` Mikulas Patocka
2018-08-08 21:51                       ` Arnd Bergmann
2018-08-09 15:29                         ` Arnd Bergmann
2018-08-03  7:11 ` Andrew Pinski
2018-08-03  7:53   ` Florian Weimer
2018-08-03  9:12     ` Szabolcs Nagy
2018-08-03  9:15     ` Ramana Radhakrishnan
2018-08-03  9:29       ` Ard Biesheuvel
2018-08-03  9:37         ` Ramana Radhakrishnan
2018-08-03  9:42         ` Richard Earnshaw (lists)
2018-08-04  0:58           ` Mikulas Patocka
2018-08-04  1:13             ` Andrew Pinski
2018-08-04 11:04               ` Mikulas Patocka
2018-08-05 18:33                 ` Florian Weimer
2018-08-06  8:02                   ` Mikulas Patocka
2018-08-06  8:10                     ` Ard Biesheuvel
2018-08-06 10:31                       ` Mikulas Patocka
2018-08-06 10:37                         ` Ard Biesheuvel
2018-08-06 10:42                           ` Mikulas Patocka
2018-08-06 10:48                             ` Ard Biesheuvel
2018-08-06 12:09                               ` Mikulas Patocka
2018-08-06 12:19                                 ` Ard Biesheuvel
2018-08-06 12:22                                   ` Ard Biesheuvel
2018-08-07 14:14                                   ` Mikulas Patocka
2018-08-07 14:40                                     ` Ard Biesheuvel
2018-08-08 19:15                                   ` Mikulas Patocka
2018-08-06 11:19                         ` Siddhesh Poyarekar
2018-08-06 11:29                           ` Ard Biesheuvel
2018-08-06 14:26                   ` Tulio Magno Quites Machado Filho
2018-08-05 21:51                 ` Pavel Machek
2018-08-06 14:30                   ` Mikulas Patocka
2018-08-03 11:24         ` David Laight
2018-08-03 12:04           ` Mikulas Patocka
2018-08-03 13:04             ` David Laight
2018-08-05 14:36               ` Mikulas Patocka
2018-08-06 10:18                 ` David Laight
2018-08-07 14:07                   ` Mikulas Patocka
2018-08-07 14:33                     ` David Laight
2018-08-08 14:21                       ` Mikulas Patocka
2018-08-03 13:20     ` Mikulas Patocka
2018-08-03 13:31   ` Mikulas Patocka
2018-08-03 14:17     ` Richard Earnshaw (lists)
2018-08-05 21:36   ` Pavel Machek
2018-08-06  8:04     ` Ramana Radhakrishnan
2018-08-06  8:44       ` Pavel Machek
2018-08-06  9:11         ` Ard Biesheuvel

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