Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <14f922495a09898017e4db3baed5b434acadac12.camel@xry111.site>
Subject: Re: [PATCH V11 09/22] LoongArch: Add boot and setup routines
From:   Xi Ruoyao <xry111@xry111.site>
To:     Huacai Chen <chenhuacai@loongson.cn>,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Airlie <airlied@linux.ie>,
        Jonathan Corbet <corbet@lwn.net>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc:     linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, Xuefeng Li <lixuefeng@loongson.cn>,
        Yanteng Si <siyanteng@loongson.cn>,
        Huacai Chen <chenhuacai@gmail.com>,
        Guo Ren <guoren@kernel.org>, Xuerui Wang <kernel@xen0n.name>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        linux-efi@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>
Date:   Tue, 24 May 2022 16:27:13 +0800
In-Reply-To: <20220518092619.1269111-10-chenhuacai@loongson.cn>
References: <20220518092619.1269111-1-chenhuacai@loongson.cn>
         <20220518092619.1269111-10-chenhuacai@loongson.cn>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.1 
MIME-Version: 1.0
Precedence: bulk

On Wed, 2022-05-18 at 17:26 +0800, Huacai Chen wrote:
> Currently an existing interface between the kernel and the bootloader
> is=C2=A0 implemented. Kernel gets 2 values from the bootloader, passed in
> registers a0 and a1; a0 is an "EFI boot flag" distinguishing UEFI and
> non-UEFI firmware, while a1 is a pointer to an FDT with systable,
> memmap, cmdline and initrd information.

If I understand this correctly, we can:

- set a0 to 0
- set a1 a pointer (virtual address or physical address?) to the FDT
with these information

in the bootloader before invoking the kernel, then it will be possible
to boot this kernel w/o firmware update?

I'd prefer to receive a firmware update anyway, but we need an
alternative if some vendor just say "no way, our customized distro works
fine and you should use it".  (I'm not accusing LoongArch: such annoying
behavior is common among vendors of all architectures, and even worse
with x86 because they often say "just use Windoge".)
--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University