Received-SPF: pass (google.com: domain of linux-kernel+bounces-9506-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Message-ID: <ced9897c5db7ea22313d58ba95590e634e98e54b.camel@ew.tq-group.com>
Subject: Re: [PATCH] powerpc/6xx: set High BAT Enable flag on G2 cores
From: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>, "Aneesh Kumar K.V"
	 <aneesh.kumar@kernel.org>, "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>, 
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, 
	linux@ew.tq-group.com, Christophe Leroy <christophe.leroy@csgroup.eu>
Date: Fri, 22 Dec 2023 09:34:06 +0100
In-Reply-To: <875y0rkpe1.fsf@mail.lhotse>
References: <20231221124538.159706-1-matthias.schiffer@ew.tq-group.com>
	 <875y0rkpe1.fsf@mail.lhotse>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.4-0ubuntu2 
Precedence: bulk
MIME-Version: 1.0

On Fri, 2023-12-22 at 12:16 +1100, Michael Ellerman wrote:
> Matthias Schiffer <matthias.schiffer@ew.tq-group.com> writes:
> > MMU_FTR_USE_HIGH_BATS is set for G2-based cores (G2_LE, e300cX), but th=
e
> > high BATs need to be enabled in HID2 to work. Add register definitions
> > and introduce a G2 variant of __setup_cpu_603.
> >=20
> > This fixes boot on CPUs like the MPC5200B with STRICT_KERNEL_RWX enable=
d.
>=20
> Nice find.
>=20
> Minor nit on naming. The 32-bit code mostly uses the numeric names, eg.
> 603, 603e, 604 etc. Can we stick with that, rather than using "G2"?
>=20
> Wikipedia says G2 =3D=3D 603e. But looking at your patch you're not chang=
ing
> all the 603e cores, so I guess it's not that clear cut?
>=20
> If using "G2" makes the most sense then it would be nice to update
> Documentation/arch/powerpc/cpu_families.rst to mention it (not asking
> you to do it necessarily, more a note for us).

According to the 603e manual I could find (MPR603EUM-01), the HID2 register=
 does not exist in the
original 603e cores - the register was only added by Freescale in its exten=
ded implementations.

The manual of the MPC5200 calls its core an "e300", but that seems to be an=
 older implementation
than the "e300c[1-4]" cores described in the "e300" manual. I'm not sure if=
 "e300" (without "cX")
and "G2_LE" are synonymous.

So AFAIR either "G2" or "e300" could be an appropriate name for the family,=
 but which is better I
can't say.

Regards,
Matthias


>=20
> cheers

--=20
TQ-Systems GmbH | M=C3=BChlstra=C3=9Fe 2, Gut Delling | 82229 Seefeld, Germ=
any
Amtsgericht M=C3=BCnchen, HRB 105018
Gesch=C3=A4ftsf=C3=BChrer: Detlef Schneider, R=C3=BCdiger Stahl, Stefan Sch=
neider
https://www.tq-group.com/