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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Thu, 14 Jul 2022 12:52:48 -0400
Message-ID: <CADnq5_ME1DsZsmC1NbHOyzfKbBp_jcKycG7Fh1HMN8y3AejWKg@mail.gmail.com>
Subject: Re: Linux 5.19-rc6
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Harry Wentland <harry.wentland@amd.com>,
        Leo Li <sunpeng.li@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Balbir Singh <bsingharora@gmail.com>,
        Daniel Axtens <dja@axtens.net>,
        Paul Mackerras <paulus@ozlabs.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>
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On Wed, Jul 13, 2022 at 5:32 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Wed, Jul 13, 2022 at 2:01 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> >
> > If you want to apply Guenter's patch original patch:
> > https://patchwork.freedesktop.org/patch/490184/
> > That's fine with me.
>
> Honestly, by this time I feel that it's too little, too late.
>
> The ppc people apparently didn't care at all about the fact that this
> driver didn't compile.
>
> At least Michael Ellerman and Daniel Axtens were cc'd on that thread
> with the proposed fix originally.
>
> I don't see any replies from ppc people as to why it happened, even
> though apparently a bog-standard "make allmodconfig" just doesn't
> build.
>
> I'd try it myself, since I do have a cross-build environment for some
> earlier cross-build verification I did.
>
> But since my upgrade to F36 it now uses gcc-12, and possibly due to
> that I get hundreds of errors long before I get to any drm drivers:
>
>   Cannot find symbol for section 19: .text.create_section_mapping.
>   arch/powerpc/mm/mem.o: failed
>   ...
>   Cannot find symbol for section 19: .text.cpu_show_meltdown.
>   drivers/base/cpu.o: failed
>   Error: External symbol 'memset' referenced from prom_init.c
>
> this cross environment used to work for me, but something changed (I
> mention gcc-12, but honestly, that's based on nothing at all, except
> for the few problems it caused on x86-64. It could be something
> entirely unrelated, but it does look like some bad interaction with
> -ffunction-sections).
>
> So considering that the ppc people ignored this whole issue since the
> merge window, I think it's entirely unreasonable to then apply a
> ppc-specific patch for this at this time, when people literally asked
> "why is this needed", and there was no reply from the powerpc side.
>
> Does any of that sound like "we should support this driver on powerpc" to you?

Fair enough.  I don't have a strong opinion on the matter.  Users will
hopefully likely notice the failure after release because most people
don't test until after a release and then we'll apply the fix and
re-enable it for 5.20 so that would leave 5.19 broken for PPC64 users
which would not be ideal.  But as you said, no one has cared up to
this point.

Alex

>
>                  Linus