linux-kernel - Re: [RFT/RFC PATCH v3 3/5] cpu-topology: Move cpu topology code to common code.

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Date:   Tue, 16 Apr 2019 14:23:24 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Atish Patra <atish.patra@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jeffrey Hugo <jhugo@...eaurora.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>,
        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>,
        Will Deacon <will.deacon@....com>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [RFT/RFC PATCH v3 3/5] cpu-topology: Move cpu topology code to
 common code.

On Mon, Apr 15, 2019 at 03:08:45PM -0700, Atish Patra wrote:
> On 4/15/19 8:27 AM, Sudeep Holla wrote:
> > Hi Atish,
> >
> > Thanks again for doing this. Overall changes look good except a couple
> > of minor nit, see below.
> >
> > On Wed, Mar 20, 2019 at 04:48:04PM -0700, Atish Patra wrote:
> > > Both RISC-V & ARM64 are using cpu-map device tree to describe
> > > their cpu topology. It's better to move the relevant code to
> > > a common place instead of duplicate code.
> > >
> > > Signed-off-by: Atish Patra <atish.patra@....com>
> > > Tested-by: Jeffrey Hugo <jhugo@...eaurora.org>
> > > ---
> > >   arch/arm64/include/asm/topology.h |  23 ---
> > >   arch/arm64/kernel/topology.c      | 303 +-----------------------------
> > >   drivers/base/arch_topology.c      | 298 ++++++++++++++++++++++++++++-
> > >   drivers/base/topology.c           |   1 +
> > >   include/linux/arch_topology.h     |  28 +++
> > >   5 files changed, 330 insertions(+), 323 deletions(-)
> > >
> >
> > [...]
> >
> > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> > > index edfcf8d9..6cc6a860 100644
> > > --- a/drivers/base/arch_topology.c
> > > +++ b/drivers/base/arch_topology.c
> > > @@ -6,8 +6,8 @@
> > >    * Written by: Juri Lelli, ARM Ltd.
> > >    */
> > > -#include <linux/acpi.h>
> > >   #include <linux/arch_topology.h>
> > > +#include <linux/acpi.h>
> > >   #include <linux/cpu.h>
> > >   #include <linux/cpufreq.h>
> > >   #include <linux/device.h>
> > > @@ -16,6 +16,11 @@
> > >   #include <linux/string.h>
> > >   #include <linux/sched/topology.h>
> > >   #include <linux/cpuset.h>
> > > +#include <linux/cpumask.h>
> > > +#include <linux/init.h>
> > > +#include <linux/percpu.h>
> > > +#include <linux/sched.h>
> > > +#include <linux/smp.h>
> > >   DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
> > > @@ -278,3 +283,294 @@ static void parsing_done_workfn(struct work_struct *work)
> > >   #else
> > >   core_initcall(free_raw_capacity);
> > >   #endif
> > > +
> > > +#if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
> >
> > Why can't the above one be just GENERIC_ARCH_TOPOLOGY ?
> > I may be missing to find it myself, but would like to know.
> >
> GENERIC_ARCH_TOPOLOGY is now used for both RISCV, ARM & ARM64.
> The below functions under this #ifdef have different implementation for ARM
> and ARM64.
>
> parse_dt_topology
> cpu_coregroup_mask
> update_siblings_masks
>
> While we can combine the later two functions and move them to common code as
> well, parse_dt_topology is significantly different.
>

Sure, had a quick glance and indeed they may look different, but won't
it defeat the purpose of this binding consolidation ?

> That's why we need some kind of #ifdef or renaming of parse_dt_topology for
> ARM32 code.
>

I am fine if we want to take this up later to keep the impact minimum.
But cpu_coregroup_mask and update_siblings_masks can and must be unified.
In fact the existing generic version must work on ARM32 too.

> Thanks for the review!!
>

You are welcome.

--
Regards,
Sudeep