linux-kernel - Re: [Nouveau] nouveau broken on Riva TNT2 in 5.9.0-rc8: GPU not supported on big-endian

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Message-Id: <202010282115.32811.linux@zary.sk>
Date:   Wed, 28 Oct 2020 21:15:32 +0100
From:   Ondrej Zary <linux@...y.sk>
To:     Karol Herbst <kherbst@...hat.com>
Cc:     Ilia Mirkin <imirkin@...m.mit.edu>,
        nouveau <nouveau@...ts.freedesktop.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        "dri-devel" <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Nouveau] nouveau broken on Riva TNT2 in 5.9.0-rc8: GPU not supported on big-endian

On Saturday 10 October 2020 02:02:42 Karol Herbst wrote:
> On Sat, Oct 10, 2020 at 12:23 AM Ilia Mirkin <imirkin@...m.mit.edu> wrote:
> >
> > On Fri, Oct 9, 2020 at 5:54 PM Karol Herbst <kherbst@...hat.com> wrote:
> > >
> > > On Fri, Oct 9, 2020 at 11:35 PM Ondrej Zary <linux@...y.sk> wrote:
> > > >
> > > > Hello,
> > > > I'm testing 5.9.0-rc8 and found that Riva TNT2 stopped working:
> > > > [    0.000000] Linux version 5.9.0-rc8+ (zary@...l) (gcc (Debian 8.3.0-6) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #326 SMP Fri Oct 9 22:31:40 CEST 2020
> > > > ...
> > > > [   14.771464] nouveau 0000:01:00.0: GPU not supported on big-endian
> > > > [   14.771782] nouveau: probe of 0000:01:00.0 failed with error -38
> > > >
> > > > big-endian? WTF? The machine is x86.
> > > >
> > >
> > > mhh, we reworked the endianess checks a bit and apparently that broke
> > > something... I will give it some thoughts, but could you be so kind
> > > and create an mmiotrace under 5.9 with nouveau? You won't need to
> > > start X or anything while doing it. Just enable the trace and modprobe
> > > nouveau and collect the trace.
> >
> > Looks like nvkm_device_endianness unconditionally reads out 0x4. I
> > don't think that reg is there pre-NV11. At least NV4, NV5, NV10 and
> > maybe NV15 (which is logically pre-NV11) don't support big-endian
> > mode. Not sure about NV1A, which was the IGP of the series and IIRC
> > logically pre-NV11 as well (but clearly could only be used with x86
> > chips, since it was part of the motherboard).
> >
> > Aha, it's documented in rnndb:
> >
> > https://github.com/envytools/envytools/blob/master/rnndb/bus/pmc.xml
> > <reg32 offset="0x004" name="ENDIAN" variants="NV1A-"/>
> >
> 
> ohh, I should have checked there.. yeah, will write a fix for it then.
> Before my patch we just always tried to switch it, but never threw an
> error.

Any progress with the patch?

-- 
Ondrej Zary