Re: [External] [PATCH v2 1/3] riscv: obtain ACPI RSDP from FFI.

From: "Björn Töpel" <bjorn@kernel.org>
To: 运辉崔 <cuiyunhui@bytedance.com>,
	"Jessica Clarke" <jrtc27@jrtc27.com>,
	"Emil Renner Berthing" <emil.renner.berthing@gmail.com>
Cc: Andrew Jones <ajones@ventanamicro.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	rminnich@gmail.com, Mark Rutland <mark.rutland@arm.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Len Brown <lenb@kernel.org>,
	jdelvare@suse.com, yc.hung@mediatek.com,
	angelogioacchino.delregno@collabora.com,
	allen-kh.cheng@mediatek.com,
	pierre-louis.bossart@linux.intel.com, tinghan.shen@mediatek.com,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-acpi@vger.kernel.org, geshijian@bytedance.com,
	weidong.wd@bytedance.com
Subject: Re: [External] [PATCH v2 1/3] riscv: obtain ACPI RSDP from FFI.
Date: Wed, 05 Jul 2023 16:42:33 +0200	[thread overview]
Message-ID: <87bkgql8rq.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <50F3BD62-78F1-456E-A44A-0C7D9A2D4113@jrtc27.com>

Jessica Clarke <jrtc27@jrtc27.com> writes:

> On 3 Jul 2023, at 19:58, Emil Renner Berthing <emil.renner.berthing@gmail.com> wrote:
>> 
>> On Mon, 3 Jul 2023 at 15:33, 运辉崔 <cuiyunhui@bytedance.com> wrote:
>>> 
>>> Hi drew,
>>> 
>>> On Mon, Jul 3, 2023 at 9:01 PM Andrew Jones <ajones@ventanamicro.com> wrote:
>>>> 
>>>> 
>>>> (This is a reply to a non-existent cover letter.)
>>> 
>>> This has been discussed many times with Ard, Please refer to :
>>> https://patches.linaro.org/project/linux-acpi/patch/20230426034001.16-1-cuiyunhui@bytedance.com/
>> 
>> Hi Yunhui,
>> 
>> From that discussion it was mentioned that that arm supports 3 methods
>> of booting:
>>  direct + devicetree
>>  EFI + devicetree
>>  EFI + ACPI
>> ..but not
>>  direct + ACPI
>> 
>> To me it isn't obvious from that or this thread, and since arm seems
>> to be doing fine without the 4th option I'm curious why that's
>> necessary on riscv?
>
> If anything we should be removing option 1, because that’s not a
> cross-OS standard (though RISC-V’s SBI direct booting is at least not
> tied to the OS). Any application-class platform spec is going to
> mandate EFI, because, whatever your thoughts of EFI are, that is *the*
> standard. And if you’re willing to pick up all the complexity of ACPI,
> what’s a bit of EFI (especially if you only go for a minimal one a la
> U-Boot)?

Well said!

Yunhui, why not simply add a minimal UEFI stub to Coreboot (like Jess
points out above)?

IMO what U-boot (or
https://github.com/cloud-hypervisor/rust-hypervisor-firmware if you're
into Rust ;-)) is doing, and just having a small UEFI shim is the way to
go.

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