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From: Morten Rasmussen <morten.rasmussen@arm.com>
To: Atish Patra <atish.patra@wdc.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, Albert Ou <aou@eecs.berkeley.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Juri Lelli <juri.lelli@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Dmitriy Cherkasov <dmitriy@oss-tech.org>,
	Anup Patel <anup@brainfault.org>,
	Palmer Dabbelt <palmer@sifive.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	Jeremy Linton <jeremy.linton@arm.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	"Peter Zijlstra \(Intel\)" <peterz@infradead.org>,
	Rob Herring <robh+dt@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	linux-riscv@lists.infradead.org, Ingo Molnar <mingo@kernel.org>,
	"moderated list:ARM64 PORT \(AARCH64 ARCHITECTURE\)"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFT PATCH v1 0/4] Unify CPU topology across ARM64 & RISC-V
Date: Fri, 7 Dec 2018 13:45:21 +0000
Message-ID: <20181207134509.GA5913@e105550-lin.cambridge.arm.com> (raw)
In-Reply-To: <1543534100-3654-1-git-send-email-atish.patra@wdc.com>

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

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  parent reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-29 23:28 Atish Patra
2018-11-29 23:28 ` [RFT PATCH v1 1/4] Documentation: DT: arm: add support for sockets defining package boundaries Atish Patra
2018-12-03 16:46   ` Sudeep Holla
2018-12-12  2:18   ` Rob Herring
2018-11-29 23:28 ` [RFT PATCH v1 2/4] dt-binding: cpu-topology: Move cpu-map to a common binding Atish Patra
2018-12-03 16:55   ` Sudeep Holla
2018-12-03 17:23     ` Atish Patra
2018-12-03 17:33       ` Sudeep Holla
2018-12-03 17:40         ` Atish Patra
2018-12-12  2:21       ` Rob Herring
2018-12-12  2:31   ` Rob Herring
2018-12-12 18:23     ` Atish Patra
2018-11-29 23:28 ` [RFT PATCH v1 3/4] cpu-topology: Move cpu topology code to common code Atish Patra
2018-12-03 16:58   ` Will Deacon
2018-12-03 17:12     ` Sudeep Holla
2018-12-04  9:50       ` Juri Lelli
2018-12-03 17:16   ` Sudeep Holla
2018-12-03 17:31     ` Atish Patra
2018-11-29 23:28 ` [RFT PATCH v1 4/4] RISC-V: Parse cpu topology during boot Atish Patra
2018-12-03 16:59   ` Sudeep Holla
2018-12-05 17:53 ` [RFT PATCH v1 0/4] Unify CPU topology across ARM64 & RISC-V Jeffrey Hugo
2018-12-11  0:26   ` Atish Patra
2018-12-07 13:45 ` Morten Rasmussen [this message]
2018-12-07 15:04   ` Sudeep Holla
2018-12-11  0:11   ` Atish Patra

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