[PATCH 00/12] Some improvements on boot sequence

[Anup Patel]

On Fri, Jun 20, 2025 at 5:52 PM Xiang W <wxjstz at 126.com> wrote:
>
> 在 2025-06-16一的 20:20 +0800，Xiang W写道：
> > 在 2025-06-16一的 17:25 +0530，Anup Patel写道：
> > > On Wed, Jun 11, 2025 at 5:42 PM Xiang W <wxjstz at 126.com> wrote:
> > > >
> > > > This series of patches mainly merges init_coldboot and init_warm_startup,
> > >
> > > The existing code of having clearly separate coldboot, warm_startup, and
> > > warm_resume paths are straightforward to understand and maintain. Even,
> > > Linux has separate start_kernel() (for boot/primary HART), smp_callin()
> > > (for non-boot/secondary HARTs) and __cpu_resume_enter() (for HART
> > > resume).
> > >
> > > > and separates sbi_hsm_hart_wait from sbi_hsm_init, so that non-coldboot
> > > > HART can perform more initialization tasks before entering HSM wait. In
> > > > order to improve some multi HARTs related codes.
> > >
> > > Performing more initialization on non-coldboot HART before
> > > sbi_hsm_hart_wait() is redundant because non-coldboot HART
> > > will have to anyway wait until coldboot HART uses SBI HSM
> > > start call.
> > >
> > > On the contrary, doing sbi_hsm_hart_wait() as the first thing for
> > > non-coldboot HART ensures that HART is fully initialized only
> > > after coldboot HART decides to bring it up (via SBI HSM start)
> > > which also enables us to poweroff non-coldboot HART on
> > > platforms with full hart-hotplug.
> > >
> > > >
> > > > Xiang W (12):
> > > >   lib: sbi: Add coldboot parameters to some initialization functions
> > > >   lib: sbi: Optimise the boot sequence
> > > >   lib: sbi: Implement synchronisation and wait between multiple HARTs
> > > >   lib: sbi: Remove wait_for_coldboot and wake_coldboot_harts
> > > >   lib: sbi: Add wait operations in some initialization functions
> > > >   lib/utils: Make fdt_parse_isa_extensions reentrant
> > > >   lib: sbi: Initialize as much as possible before sbi_hsm_init
> > > >   lib: sbi: Remove cold_boot from sbi_hsm_init
> > > >   lib: sbi: Ensure that all Harts complete sbi_hart_init
> > > >   lib/utils: Fix Zicntr detection in fdt_cpu_fixup
> > > >   lib: sbi: Fix dtbr initialization
> > > >   lib: sbi: Remove cold_boot from sbi_double_trap_init
> > >
> > > This all seems unnecessary churn and I still find it hard
> > > to understand the underlying problem.
> >
> > When initialization depends on other HART extensions, the
> > old startup process is completely unaware of other HART
> > extensions.For example, the issues fixed by PATCH10/PATCH11
> > /PATCH12 all assume that the extensions supported by HART
> > are the same.
>
> We should assume that asymmetric processors may appear.
>
> asymmetric CPU example: SpacemiT K1
>
> > Two asymmetric CPU Clusters included: Cluster0 integrates Quad
> > RISC-V SpacemiT® X60™Cores with 2.0TOPS AI-Power extension
> > while Cluster1 includes Quad RISC-V SpacemiT® X60™ Cores without
> > AI Capability
> https://docs.banana-pi.org/en/BPI-F3/SpacemiT_K1_datasheet
>
> AI Capability is achieved through custom extended IME
> https://github.com/space-mit/riscv-ime-extension-spec

To some extent we already support asymmetric harts because we
have per-hart features and capabilities detected at boot-time. There
might be some minor improvements possible but boot-flow changes
(almost all changes) in this series are not needed.

Regards,
Anup