Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
Feedback-ID: ifd894703:Fastmail
User-Agent: Cyrus-JMAP/3.9.0-alpha0-1234-gac66594aae-fm-20231122.001-gac66594a
MIME-Version: 1.0
Message-Id: <8ca730b9-fa8c-46ea-bdc5-158da0f29c3a@app.fastmail.com>
In-Reply-To: <c7cuvhuu6py5vxhhvkhekv6ned5sro4a3wzzn7v45oahfw42ud@gyqmucagt5e2>
References: <20231122182419.30633-1-fancer.lancer@gmail.com>
 <20231122182419.30633-2-fancer.lancer@gmail.com>
 <b996b542-4cd3-4f9d-b221-00b2d5ef224e@app.fastmail.com>
 <c7cuvhuu6py5vxhhvkhekv6ned5sro4a3wzzn7v45oahfw42ud@gyqmucagt5e2>
Date:   Thu, 23 Nov 2023 12:13:11 +0000
From:   "Jiaxun Yang" <jiaxun.yang@flygoat.com>
To:     "Serge Semin" <fancer.lancer@gmail.com>,
        "Arnd Bergmann" <arnd@arndb.de>
Cc:     "Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
        "Andrew Morton" <akpm@linux-foundation.org>,
        "Mike Rapoport" <rppt@kernel.org>,
        "Matthew Wilcox" <willy@infradead.org>,
        "Tiezhu Yang" <yangtiezhu@loongson.cn>,
        "Huacai Chen" <chenhuacai@kernel.org>,
        "Yinglu Yang" <yangyinglu@loongson.cn>,
        "Alexey Malahov" <Alexey.Malahov@baikalelectronics.ru>,
        "Aleksandar Rikalo" <aleksandar.rikalo@syrmia.com>,
        "Aleksandar Rikalo" <arikalo@gmail.com>,
        "Dragan Mladjenovic" <dragan.mladjenovic@syrmia.com>,
        "Chao-ying Fu" <cfu@wavecomp.com>, "Marc Zyngier" <maz@kernel.org>,
        "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/7] mips: dmi: Fix early remap on MIPS32
Content-Type: text/plain;charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk


=E5=9C=A82023=E5=B9=B411=E6=9C=8823=E6=97=A5=E5=8D=81=E4=B8=80=E6=9C=88 =
=E4=B8=8A=E5=8D=889:32=EF=BC=8CSerge Semin=E5=86=99=E9=81=93=EF=BC=9A
> Hi Arnd
>
> On Wed, Nov 22, 2023 at 08:35:01PM +0100, Arnd Bergmann wrote:
>> On Wed, Nov 22, 2023, at 19:23, Serge Semin wrote:
>> > dmi_early_remap() has been defined as ioremap_cache() which on MIPS=
32 gets
>> > to be converted to the VM-based mapping. DMI early remapping is per=
formed
>> > at the setup_arch() stage with no VM available. So calling the
>> > dmi_early_remap() for MIPS32 causes the system to crash at the earl=
y boot
>> > time. Fix that by converting dmi_early_remap() to the uncached rema=
pping
>> > which is always available on both 32 and 64-bits MIPS systems.
>> >
>> > Fixes: be8fa1cb444c ("MIPS: Add support for Desktop Management Inte=
rface (DMI)")
>> > Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
>> > ---
>> >  arch/mips/include/asm/dmi.h | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/arch/mips/include/asm/dmi.h b/arch/mips/include/asm/dm=
i.h
>> > index 27415a288adf..525aad1572d1 100644
>> > --- a/arch/mips/include/asm/dmi.h
>> > +++ b/arch/mips/include/asm/dmi.h
>> > @@ -5,7 +5,7 @@
>> >  #include <linux/io.h>
>> >  #include <linux/memblock.h>
>> >=20
>> > -#define dmi_early_remap(x, l)		ioremap_cache(x, l)
>> > +#define dmi_early_remap(x, l)		ioremap_uc(x, l)
>>=20
>
>> Please don't use ioremap_uc() in new code, we are in the (long)
>> process of removing it from the kernel for everything except
>> x86-32, and it already returns NULL on most of them.
>>=20
>> Would the normal ioremap() work for you here? It seems to
>> do the same thing as ioremap_uc() on mips and a couple of=20
>> other architectures that have not yet killed it off.
>
> Ok. Thanks for the heads up. I'll fix the patch to be using ioremap()
> in v2. ioremap_uc() is just an macro-alias of ioremap() on MIPS.

Perhaps we need to fix ioremap_cache so it can give a KSEG1 address?
AFAIK for Loongson DMI is located at cached memory so using ioremap_uc
blindly will cause inconsistency.

Thanks
- Jiaxun

>
> -Serge(y)
>
>>=20
>>    Arnd

--=20
- Jiaxun