linux-kernel - Re: [PATCH 11/13] arm: npcm: drop selecting non-existing ARM_ERRATA

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Message-ID: <CAKXUXMyrhrM2o-OEW_qTTKjfKgxt-Z6Nt69geU80AoFnM1OuMA@mail.gmail.com>
Date:   Tue, 2 Nov 2021 08:31:40 +0100
From:   Lukas Bulwahn <lukas.bulwahn@...il.com>
To:     Joel Stanley <joel@....id.au>
Cc:     Arnd Bergmann <arnd@...db.de>, Tomer Maimon <tmaimon77@...il.com>,
        Avi Fishman <avifishman70@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Sekhar Nori <nsekhar@...com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Linus Walleij <linusw@...nel.org>,
        Imre Kaloz <kaloz@...nwrt.org>,
        Krzysztof Halasa <khalasa@...p.pl>,
        Tali Perry <tali.perry1@...il.com>,
        Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        kernel-janitors <kernel-janitors@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 11/13] arm: npcm: drop selecting non-existing ARM_ERRATA_794072

On Fri, Oct 29, 2021 at 8:36 AM Joel Stanley <joel@....id.au> wrote:
>
> On Thu, 28 Oct 2021 at 14:57, Arnd Bergmann <arnd@...db.de> wrote:
> >
> > On Thu, Oct 28, 2021 at 4:19 PM Lukas Bulwahn <lukas.bulwahn@...il.com> wrote:
> > >
> > > There is no and never was a Kconfig for ARM_ERRATA_794072 in the kernel
> > > tree. So, there is no need to select ARM_ERRATA_794072 in
> > > ./arch/arm/mach-npcm/Kconfig.
> > >
> > > Simply drop selecting the non-existing ARM_ERRATA_794072.
> > >
> > > This issue was discovered with ./scripts/checkkconfigsymbols.py.
> > >
> > > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
> > > ---
> >
> > Could this be a typo? Maybe we need to enable a different errata workaround
> > here, or maybe that code is actually needed and has to get sent.
>
> Doing some searching, u-boot had a workaround for something called
> ARM_ERRATA_794072.
>
> https://github.com/u-boot/u-boot/commit/f71cbfe3ca5d2ad20159871700e8e248c8818ba8
>
> Lore has the review history for that patch:
>
> https://lore.kernel.org/all/6be32e0b5b454ed7b609317266a8e798@BLUPR03MB358.namprd03.prod.outlook.com/
>
> It looks like it's the same workaround as ARM_ERRATA_742230, which the
> kernel does implement.
>
> It would be good to hear from the Nuvoton people, or an Arm person.
>

I will happily update the patch to select ARM_ERRATA_742230 instead of
the dead non-existing ARM_ERRATA_794072.

In contrast to the current patch that basically only cleans up "dead
config" and has no effective functional change, the new patch would
change the behaviour. I cannot test this patch (beyond some basic
compile test) on the hardware; so, we certainly need someone to have
that hardware, knows how to test it or confirm otherwise that we
should select the ARM_ERRATA_742230 fix for this hardware.

The current patch should be subsumed by the new patch; the submission
of the new patch is deferred until that person shows up. Let's see.

Lukas