linux-kernel - Re: [RFT/RFC PATCH v3 0/5] Unify CPU topology across ARM & RISC-V

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Message-ID: <12c9f8b0-cdeb-2b9c-5662-6c5a08cd0a95@wdc.com>
Date:   Wed, 10 Apr 2019 15:49:54 -0700
From:   Atish Patra <atish.patra@....com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Dmitriy Cherkasov <dmitriy@...-tech.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Johan Hovold <johan@...nel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Otto Sabart <ottosabart@...erm.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [RFT/RFC PATCH v3 0/5] Unify CPU topology across ARM & RISC-V

On 3/20/19 4:48 PM, Atish Patra wrote:
> The cpu-map DT entry in ARM can describe the CPU topology in much better
> way compared to other existing approaches. RISC-V can easily adopt this
> binding to represent its own CPU topology. Thus, both cpu-map DT
> binding and topology parsing code can be moved to a common location so
> that RISC-V or any other architecture can leverage that.
> 
> The relevant discussion regarding unifying cpu topology can be found in
> [1].
> 
> arch_topology seems to be a perfect place to move the common code. I
> have not introduced any significant functional changes in the moved code.
> The only downside in this approach is that the capacity code will be
> executed for RISC-V as well. But, it will exit immediately after not
> able to find the appropriate DT node. If the overhead is considered too
> much, we can always compile out capacity related functions under a
> different config for the architectures that do not support them.
> 
> There was an opportunity to unify topology data structure for ARM32 done
> by patch 3/4. But, I refrained from making any other changes as I am not
> very well versed with original intention for some functions that
> are present in arch_topology.c. I hope this patch series can be served
> as a baseline for such changes in the future.
> 
> The patches have been tested for RISC-V and compile tested for ARM64,
> ARM32 & x86.
> 
> The socket change[2] is also now part of this series.
> 
> [1] https://lkml.org/lkml/2018/11/6/19
> [2] https://lkml.org/lkml/2018/11/7/918
> 
> QEMU changes for RISC-V topology are available at
> 
> https://github.com/atishp04/qemu/tree/riscv_topology_dt
> 
> HiFive Unleashed DT with topology node is available here.
> https://github.com/atishp04/opensbi/tree/HiFive_unleashed_topology
> 
> It can be verified with OpenSBI with following additional compile time
> option.
> 
> FW_PAYLOAD_FDT="unleashed_topology.dtb"
> 
> Changes from v2->v3
> 1. Cover letter update with experiment DT for topology changes.
> 2. Added the patch for [2].
> 
> Changes from v1->v2
> 1. ARM32 can now use the common code as well.
> 
> Atish Patra (4):
> dt-binding: cpu-topology: Move cpu-map to a common binding.
> cpu-topology: Move cpu topology code to common code.
> arm: Use common cpu_topology
> RISC-V: Parse cpu topology during boot.
> 
> Sudeep Holla (1):
> Documentation: DT: arm: add support for sockets defining package
> boundaries
> 
> .../topology.txt => cpu/cpu-topology.txt}     | 134 ++++++--
> arch/arm/include/asm/topology.h               |  22 +-
> arch/arm/kernel/topology.c                    |  10 +-
> arch/arm64/include/asm/topology.h             |  23 --
> arch/arm64/kernel/topology.c                  | 303 +-----------------
> arch/riscv/Kconfig                            |   1 +
> arch/riscv/kernel/smpboot.c                   |   3 +
> drivers/base/arch_topology.c                  | 298 ++++++++++++++++-
> drivers/base/topology.c                       |   1 +
> include/linux/arch_topology.h                 |  36 +++
> 10 files changed, 453 insertions(+), 378 deletions(-)
> rename Documentation/devicetree/bindings/{arm/topology.txt => cpu/cpu-topology.txt} (66%)
> 
> --
> 2.21.0
> 
> 

Ping?

Specifically, patch 3 & 4 affects ARM & ARM64. Any tests on real 
hardware would be great.

Regards,
Atish