From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] [v3] powerpc/4xx: work around CHIP11 errata in a more PAGE_SIZE-friendly way From: Michael Ellerman To: Hollis Blanchard In-Reply-To: <1227557235.17746.25.camel@localhost.localdomain> References: <4b6790c7a989dce8c200000687275224@bga.com> <84e16946c1ed4b782568f6492931512a@bga.com> <200811141609.44161.hollisb@us.ibm.com> <1227557235.17746.25.camel@localhost.localdomain> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-QTZOR8VqaJtq43VWoXMH" Date: Tue, 25 Nov 2008 11:10:28 +1100 Message-Id: <1227571828.20022.5.camel@localhost> Mime-Version: 1.0 Cc: Milton Miller , Wolfgang Denk , Ilya Yanok , linux-ppc Reply-To: michael@ellerman.id.au List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-QTZOR8VqaJtq43VWoXMH Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Mon, 2008-11-24 at 14:07 -0600, Hollis Blanchard wrote: > On Fri, 2008-11-14 at 16:09 -0600, Hollis Blanchard wrote: > >=20 > > If this is all too much, then I'm close to giving up and burning a > > 64KB page, which requires only ALIGN_DOWN() in the kernel. >=20 > ppc: force memory size to be a multiple of PAGE_SIZE >=20 > Ensure that total memory size is page-aligned, because otherwise > bootmem.c gets upset. >=20 > This error case was triggered by using 64 KiB pages in the kernel while > arch/powerpc/boot/4xx.c arbitrarily reduced the amount of memory by 4096 = (to > work around the "CHIP11" errata which affects the last 256 bytes of physi= cal memory). >=20 > Signed-off-by: Hollis Blanchard > --- > This is on a common code path, and lmb_enforce_memory_limit() will now > always take action, so wider testing would be good. >=20 > This patch supercedes http://patchwork.ozlabs.org/patch/8211/ . >=20 > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c > --- a/arch/powerpc/kernel/prom.c > +++ b/arch/powerpc/kernel/prom.c > @@ -1200,6 +1200,11 @@ void __init early_init_devtree(void *par > early_reserve_mem(); > phyp_dump_reserve_mem(); > =20 > + /* Ensure that total memory size is page-aligned, because otherwise > + * bootmem.c gets upset. */ > + lmb_analyze(); > + memory_limit =3D lmb_phys_mem_size() & PAGE_MASK; All of the current code using memory_limit looks like it'll be safe with this change, although there are several cases of this we could remove: if (memory_limit && ) Because memory_limit will now always be true. Still, I think it would be better to only set memory_limit when the mem size is not a multiple of the PAGE_SIZE - so that memory_limit retains it's function as both the value of the limit and a boolean. cheers --=20 Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person --=-QTZOR8VqaJtq43VWoXMH Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEABECAAYFAkkrQnQACgkQdSjSd0sB4dL5tQCfZwshklvLovD4NiD/ULTft8Oy 8pEAniVaRA2e4KwsbQURYITR/fvqOABC =QGFM -----END PGP SIGNATURE----- --=-QTZOR8VqaJtq43VWoXMH--