linux-kernel - Re: [RFC 0/3] Unify CPU topology across ARM64 & RISC-V

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Date:   Mon, 19 Nov 2018 09:46:44 -0800
From:   Atish Patra <atish.patra@....com>
To:     Jeffrey Hugo <jhugo@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Damien Le Moal <Damien.LeMoal@....com>,
        "juri.lelli@....com" <juri.lelli@....com>,
        "anup@...infault.org" <anup@...infault.org>,
        "palmer@...ive.com" <palmer@...ive.com>,
        "jeremy.linton@....com" <jeremy.linton@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "sudeep.holla@....com" <sudeep.holla@....com>,
        "mick@....forth.gr" <mick@....forth.gr>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC 0/3] Unify CPU topology across ARM64 & RISC-V

On 11/15/18 10:31 AM, Jeffrey Hugo wrote:
> On 11/8/2018 6:50 PM, 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
>> to 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.
>>
>> The socket changes[2] can be merged on top of this series or vice
>> versa.
>>
>> [1] https://lkml.org/lkml/2018/11/6/19
>> [2] https://lkml.org/lkml/2018/11/7/918
>>
>> Atish Patra (3):
>>     dt-binding: cpu-topology: Move cpu-map to a common binding.
>>     cpu-topology: Move cpu topology code to common code.
>>     RISC-V: Parse cpu topology during boot.
>>
>>    Documentation/devicetree/bindings/arm/topology.txt | 475 -------------------
>>    .../devicetree/bindings/cpu/cpu-topology.txt       | 526 +++++++++++++++++++++
>>    arch/arm64/include/asm/topology.h                  |  23 +-
>>    arch/arm64/kernel/topology.c                       | 305 +-----------
>>    arch/riscv/Kconfig                                 |   1 +
>>    arch/riscv/kernel/smpboot.c                        |   6 +-
>>    drivers/base/arch_topology.c                       | 303 ++++++++++++
>>    include/linux/arch_topology.h                      |  23 +
>>    include/linux/topology.h                           |   1 +
>>    9 files changed, 864 insertions(+), 799 deletions(-)
>>    delete mode 100644 Documentation/devicetree/bindings/arm/topology.txt
>>    create mode 100644 Documentation/devicetree/bindings/cpu/cpu-topology.txt
>>
> 
> I was interested in testing these on QDF2400, an ARM64 platform, since
> this series touches core ARM64 code and I'd hate to see a regression.
> However, I can't figure out what baseline to use to apply these.
> Different patches cause different conflicts of a variety of baselines I
> attempted.
> 
> What are these intended to apply to?
> 
I had rebased them on top of 4.20-rc1.

> Also, you might want to run them through checkpatch next time.  There
> are several whitespace errors.
> 
Sorry I missed couple of them.
Thanks for trying to test the patches. I will send a next version as Rob 
suggested. Please test that.


Regards,
Atish