Re: [PATCH 3/3] [RFC] ARM: shmobile: defconfig: Disable PL310_ERRATA_588369

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Simon Horman <horms@verge.net.au>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
	Magnus Damm <magnus.damm@gmail.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 3/3] [RFC] ARM: shmobile: defconfig: Disable PL310_ERRATA_588369
Date: Fri, 23 Aug 2019 11:49:19 +0200	[thread overview]
Message-ID: <CAMuHMdX1uryY5wbbJ7n1w2_XHdCMwLst4w-nbQw-iAxORTJyuw@mail.gmail.com> (raw)
In-Reply-To: <20190822085804.rgyjxisnznmnura5@verge.net.au>

Hi Simon,

On Thu, Aug 22, 2019 at 10:58 AM Simon Horman <horms@verge.net.au> wrote:
> On Wed, Aug 21, 2019 at 02:46:02PM +0200, Geert Uytterhoeven wrote:
> > PL310 Erratum 588369 affects PL310 cache controller revisions older than
> > r2p0.
> >
> > As Renesas ARM SoCs contain the following revisions:
> >   - SH-Mobile AG5: r3p1,
> >   - R-Mobile A1: r3p1-50rel0,
> >   - R-Car H1: r3p2,
> >   - RZ/A1: r3p2,
> >   - RZ/A2: r3p3,
> > none of them are affected, and support for the errata can be disabled
> > safely.
> >
> > The EMMA Mobile EV2 documentation doesn't mention the revision of its
> > PL310 cache controller, so this SoC might be affected.  However, the L2
> > cache controller is not enabled by Linux.
>
> If the controller is not enabled by Linux then I would think that the
> Errata is not needed. If that is true then I agree with this patch.
>
> Regarding making assumptions about the version of the PL310 cache
> controller, I suggest that we cannot assume that it is not affected
> without further information.

I agree, so this needs more investigation.

It seems this was included in shmobile_defconfig based on the old
armadillo800eav_defconfig, which enabled several errata options since
commit e0ef0984ae346c54 ("ARM: shmobile: armadillo800eva: enable all
errata for cache on defconfig").
Based on my current knowledge, PL310_ERRATA_769419 is the only one that
affects Renesas SoCs (ignoring EMEV2 for now) with a PL310, and thus
should be enabled, too.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds