linux-kernel - Re: [PATCH] powerpc/powernv/pci: remove dead code from !CONFIG

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Date:   Tue, 18 May 2021 16:13:50 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Daniel Axtens <dja@...ens.net>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Joe Perches <joe@...ches.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc/powernv/pci: remove dead code from !CONFIG_EEH

Nick Desaulniers <ndesaulniers@...gle.com> writes:
> On Thu, Apr 22, 2021 at 6:13 PM Oliver O'Halloran <oohall@...il.com> wrote:
>>
>> On Fri, Apr 23, 2021 at 9:09 AM Daniel Axtens <dja@...ens.net> wrote:
>> >
>> > Hi Nick,
>> >
>> > > While looking at -Wundef warnings, the #if CONFIG_EEH stood out as a
>> > > possible candidate to convert to #ifdef CONFIG_EEH, but it seems that
>> > > based on Kconfig dependencies it's not possible to build this file
>> > > without CONFIG_EEH enabled.
>> >
>> > This seemed odd to me, but I think you're right:
>> >
>> > arch/powerpc/platforms/Kconfig contains:
>> >
>> > config EEH
>> >         bool
>> >         depends on (PPC_POWERNV || PPC_PSERIES) && PCI
>> >         default y
>> >
>> > It's not configurable from e.g. make menuconfig because there's no prompt.
>> > You can attempt to explicitly disable it with e.g. `scripts/config -d EEH`
>> > but then something like `make oldconfig` will silently re-enable it for
>> > you.
>> >
>> > It's been forced on since commit e49f7a9997c6 ("powerpc/pseries: Rivet
>> > CONFIG_EEH for pSeries platform") in 2012 which fixed it for
>> > pseries. That moved out from pseries to pseries + powernv later on.
>> >
>> > There are other cleanups in the same vein that could be made, from the
>> > Makefile (which has files only built with CONFIG_EEH) through to other
>> > source files. It looks like there's one `#ifdef CONFIG_EEH` in
>> > arch/powerpc/platforms/powernv/pci-ioda.c that could be pulled out, for
>> > example.
>> >
>> > I think it's probably worth trying to rip out all of those in one patch?
>>
>> The change in commit e49f7a9997c6 ("powerpc/pseries: Rivet CONFIG_EEH
>> for pSeries platform") never should have been made.
>
> I'll change my patch to keep the conditionals, but use #ifdef instead
> of #if then?

Yeah, please.

I'm not sure I agree with oohal that untangling pseries/powernv from
EEH is something we should do, but let's kick that can down the road by
just fixing up the ifdef.

cheers