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Date: Mon, 10 Dec 2018 16:11:21 -0800 From: Atish Patra <atish.patra@....com> To: Morten Rasmussen <morten.rasmussen@....com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 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>, Juri Lelli <juri.lelli@....com>, "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" <linux-arm-kernel@...ts.infradead.org>, "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>, Mark Rutland <mark.rutland@....com>, Palmer Dabbelt <palmer@...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>, Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will.deacon@....com> Subject: Re: [RFT PATCH v1 0/4] Unify CPU topology across ARM64 & RISC-V On 12/7/18 5:45 AM, Morten Rasmussen wrote: > Hi, > > On Thu, Nov 29, 2018 at 03:28:16PM -0800, Atish Patra wrote: >> The cpu-map DT entry in ARM64 can describe the CPU topology in >> much better way compared to other existing approaches. RISC-V can >> easily adopt this binding to represent it's 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 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. >> >> The patches have been tested for RISC-V and compile tested for >> ARM64 & x86. > > The cpu-map bindings are used for arch/arm too, and so is > arch_topology.c. In fact, it was introduced to allow code-sharing > between arm and arm64. Applying patch three breaks arm. > > Moving the DT parsing to arch_topology.c we have to unify all three > architectures. Be aware that arm and arm64 have some differences in how > they detect cpu capacities. I think we might have to look at the split > of code between arch/* and arch_topology.c again :-/ > > Morten > Thank you for bringing this up. I will send a new version and make sure that it works on arm32 as well. Regards, Atish
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