Messages in this thread | | | Date | Fri, 3 Jun 2022 18:37:07 +0800 | Subject | Re: [PATCH V15 11/24] LoongArch: Add boot and setup routines | From | WANG Xuerui <> |
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On 6/3/22 18:02, Arnd Bergmann wrote: > On Fri, Jun 3, 2022 at 11:27 AM WANG Xuerui <kernel@xen0n.name> wrote: >> On 6/3/22 15:20, Huacai Chen wrote: >>> Add basic boot, setup and reset routines for LoongArch. Now, LoongArch >>> machines use UEFI-based firmware. The firmware passes configuration >>> information to the kernel via ACPI and DMI/SMBIOS. >>> >>> Currently an existing interface between the kernel and the bootloader >>> is 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. >>> >>> The standard UEFI boot protocol (EFISTUB) will be added later. >>> >>> Cc: linux-efi@vger.kernel.org >>> Cc: Ard Biesheuvel <ardb@kernel.org> >>> Reviewed-by: WANG Xuerui <git@xen0n.name> >>> Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com> >>> Co-developed-by: Yun Liu <liuyun@loongson.cn> >>> Signed-off-by: Yun Liu <liuyun@loongson.cn> >>> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> >> Would you please look at this patch, which has all the arch-independent >> changes backed out, and Ack if it is fit for mainlining? >> >> I communicated a little with Huacai about the approach for supporting >> alternative boot protocols down the road, and we agreed to carry the >> respective changes downstream. And if needs truly arise for modifying >> common EFI logic, we can do so in a non-rushed manner later. >> >> For the current status of the code, apparently it just accepts the >> standard efistub-shape FDT pointer from (whatever booting the image), >> and everything onwards are fully using the common code without >> modification as you can see from the diffstat. I rebased my BPI support >> patch on top of this (basically translating Loongson BPI data structures >> into the expected FDT form), and can confirm the boot can progress to >> the same point as before -- indeed the SVAM changes etc. are not >> necessary for a working system, and the code remains working. > I'm a bit lost here: Does this mean the v15 version is back to the old > pre-efistub interface and allows booting with existing firmware, or > is it now left out completely? I still see a kernel_entry() function > in head.S, and I see references to loongson_sysconf, but I don't > see if that is what gets passed in from the bootloader. It's not the same interface as in some of the very early revisions; the earlier versions relied on "struct bootparamsinterface" or BPI, while it's the same FDT-based interface to initialize EFI from, as in arch/arm64 and arch/riscv I believe. No Loongson-specific things remain now. > > I really want to make sure that without the EFI stub, there is no > other way to boot the kernel that would have to get maintained > in the long run. Yeah this is the case right now. No LoongArch bootloader that I know of can prepare the EFI stub-shaped FDT that the current code expects, and I don't know of any future Loongson plan to do that either (Loongson's previous in-house efforts all looked something different). So it's pretty safe to say the current code wouldn't get frozen once mainlined. > > Arnd
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