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Subject: Re: [External] [PATCH v3 0/4] Obtain SMBIOS and ACPI entry from FFI
From:   Jessica Clarke <jrtc27@jrtc27.com>
In-Reply-To: <CAEEQ3wnhCRnDsa2Un=J_VOo2JZqf0nMXX11okqpyhMbLAWsKJQ@mail.gmail.com>
Date:   Sat, 8 Jul 2023 04:58:49 +0100
Cc:     Dong Wei <Dong.Wei@arm.com>, Conor Dooley <conor@kernel.org>,
        =?utf-8?B?6JGb5aOr5bu6?= <geshijian@bytedance.com>,
        Sunil V L <sunilvl@ventanamicro.com>,
        Conor Dooley <conor.dooley@microchip.com>,
        ron minnich <rminnich@gmail.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        "kernel@esmil.dk" <kernel@esmil.dk>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        Mark Rutland <Mark.Rutland@arm.com>,
        "lpieralisi@kernel.org" <lpieralisi@kernel.org>,
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        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
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To:     =?utf-8?B?6L+Q6L6J5bSU?= <cuiyunhui@bytedance.com>
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On 8 Jul 2023, at 04:22, =E8=BF=90=E8=BE=89=E5=B4=94 =
<cuiyunhui@bytedance.com> wrote:
>=20
> Hey,
>=20
> On Sat, Jul 8, 2023 at 12:39=E2=80=AFAM Dong Wei <Dong.Wei@arm.com> =
wrote:
>>=20
>>=20
>>=20
>>> I don't think that's the limitation on RISC-V. BTW, how does OSPM =
find the
>>=20
>>> RSDP on ARM systems? Does it meet 5.2.5?
>>=20
>>>=20
>>=20
>>=20
>>=20
>> On Arm systems today, the ACPI RSDP is found using the UEFI =
Configuration Table. This is true for all Arm SystemReady compliant =
systems: 1) SystemReady LS: LBBRv1 is using a minimal UEFI FW to load =
LinuxBoot, that minimal UEFI FW is producing the UEFI Configuration =
Table. We are working on LBBRv2. LBBRv2 is based on Coreboot loading =
LinuxBoot. But we do not have a way today to get CoreBoot to produce =
this pointer to ACPI RSDP. Arm does not support x86 E820 BIOS interface. =
2) SystemReady IR: this solution uses DT rather than ACPI. 3) =
SystemReady ES: this solution can use UBoot or EDK2, and it requires =
ACPI. Since both UBoot and EDK2 support UEFI now, so ACPI RSDP can be =
found using the UEFI Configuration Table. 4) SystemReady SR: this =
solution typically uses EDK2 and requires ACPI, so no issue finding RSDP =
via UEFI Configuration Table.
>=20
> Looks like ARM has a similar problem,

If by =E2=80=9Cproblem=E2=80=9D you mean =E2=80=9Cthere=E2=80=99s only =
one standard that I=E2=80=99m choosing
to not follow=E2=80=9D.

> Indeed, as Ron said, many companies may encounter this issue. More
> developers are embracing Coreboot. When the platform guided by
> Coreboot requires ACPI support, they are faced with how to pass ACPI
> RSDP to Linux.

It=E2=80=99s called UEFI. EBBR=E2=80=99s requirements are pretty =
minimal.

Please just follow the one standard. Having one standard is good for
compatibility; there needs to be a very good reason beyond =E2=80=9CI =
don=E2=80=99t
like the standard=E2=80=9D to introduce a competing one and the =
fragmentation
that results from it that becomes shared pain for the ecosystem.

Jess

>> So the ACPI RSDP issue only exist if we want to remove the minimum =
UEFI FW and go to CoreBoot completely to load LinuxBoot. We are =
currently exploring how to solve that issue=E2=80=A6
>>=20
>>=20
>>=20
>> -DW
>>=20
>>=20
>>=20
>> IMPORTANT NOTICE: The contents of this email and any attachments are =
confidential and may also be privileged. If you are not the intended =
recipient, please notify the sender immediately and do not disclose the =
contents to any other person, use it for any purpose, or store or copy =
the information in any medium. Thank you.
>=20
> Thanks,
> Yunhui