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

* [RFT/RFC PATCH v3 0/5] Unify CPU topology across ARM & RISC-V
@ 2019-03-20 23:48 Atish Patra
  2019-03-20 23:48 ` [RFT/RFC PATCH v3 1/5] Documentation: DT: arm: add support for sockets defining package boundaries Atish Patra
                   ` (5 more replies)
  0 siblings, 6 replies; 17+ messages in thread
From: Atish Patra @ 2019-03-20 23:48 UTC (permalink / raw)
  To: linux-kernel
  Cc: Mark Rutland, Rafael J. Wysocki, Peter Zijlstra (Intel),
	Catalin Marinas, Palmer Dabbelt, Will Deacon, Atish Patra,
	linux-riscv, Ingo Molnar, Dmitriy Cherkasov, Anup Patel,
	Morten Rasmussen, devicetree, Albert Ou, Johan Hovold,
	Rob Herring, Paul Walmsley, Ard Biesheuvel, Greg Kroah-Hartman,
	Jeremy Linton, Otto Sabart, Sudeep Holla

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

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