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Message-ID: <20140813222553.GA685@e102568-lin.cambridge.arm.com>
Date: Wed, 13 Aug 2014 23:25:53 +0100
From: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To: Juri Lelli <juri.lelli@....com>
Cc: Russell King - ARM Linux <linux@....linux.org.uk>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Juri Lelli <juri.lelli@...il.com>
Subject: Re: [PATCH] cpuidle/cpuidle-big_little: fix reading cpu id part
number
On Wed, Aug 13, 2014 at 12:14:40PM +0100, Juri Lelli wrote:
> On 13/08/14 11:44, Russell King - ARM Linux wrote:
> > On Wed, Aug 13, 2014 at 11:04:13AM +0100, Juri Lelli wrote:
> >> Thanks a lot for the comment. Does what below address it?
> >
> > Yes, thanks, but a few of nitpicks though.
> >
> >> +/*
> >> + * smp_cpuid_part() - return part id for a given cpu
> >> + *
> >> + * @cpu: logical cpu id
> >> + *
> >> + * Return: part id of logical cpu passed as argument
> >> + *
> >> + */
> >
> > If this is supposed to be a kerneldoc-compatible comment, please read
> > Documentation/kernel-doc-nano-HOWTO.txt for the correct format.
> >
> >> +static inline unsigned int smp_cpuid_part(int cpu)
> >> +{
> >> + struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpu);
> >> +
> >> + return is_smp() ? (cpu_info->cpuid & ARM_CPU_PART_MASK) :
> >
> > Parens are not required, and there's a double space before &.
> >
> > The BNF for the ?: operator is:
> >
> > cond-expr:
> > log-or-expr ? expr : cond-expr
> >
> > So the compiler knows that whatever is between the ? and : is a single
> > expression, and the parens are surplus.
> >
> >> -static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int cpu_id)
> >> +static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int match_id)
> >
> > If we're changing the name, "part_id" would probably be better than the
> > opaque "match_id" here.
> >
>
> Right, thanks! What follows has those fixed. Should I send it as a new post?
I think that you can drop it as a v2 on LAKML as a separate post, and
unless Russell has any further objections then put it in his patch
system.
Thanks,
Lorenzo
>
> Thanks,
>
> - Juri
>
> From 61b88de0f021213f894e843c8e4673203f953ca9 Mon Sep 17 00:00:00 2001
> From: Juri Lelli <juri.lelli@....com>
> Date: Thu, 7 Aug 2014 17:26:54 +0100
> Subject: [PATCH] cpuidle/cpuidle-big_little: fix reading cpu id part number
>
> Commit af040ffc9ba1e079ee4c0748aff64fa3d4716fa5 by Russell King changed
> ARM_CPU_PART_X masks, and the way they are returned and checked against.
> Usage of read_cpuid_part_number() is now deprecated, and calling places
> updated accordingly. This actually broke cpuidle-big_little initialization,
> as bl_idle_driver_init() performs a check using and hardcoded mask on
> cpu_id.
>
> Create an interface to perform the check (that is now even easier to read).
> Define also a proper mask (ARM_CPU_PART_MASK) that makes this kind of checks
> cleaner and helps preventing bugs in the future. Update usage accordingly.
>
> Signed-off-by: Juri Lelli <juri.lelli@....com>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> ---
> arch/arm/include/asm/cputype.h | 3 ++-
> arch/arm/include/asm/smp_plat.h | 15 +++++++++++++++
> drivers/cpuidle/cpuidle-big_little.c | 13 +++----------
> 3 files changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h
> index 963a251..819777d 100644
> --- a/arch/arm/include/asm/cputype.h
> +++ b/arch/arm/include/asm/cputype.h
> @@ -74,6 +74,7 @@
> #define ARM_CPU_PART_CORTEX_A12 0x4100c0d0
> #define ARM_CPU_PART_CORTEX_A17 0x4100c0e0
> #define ARM_CPU_PART_CORTEX_A15 0x4100c0f0
> +#define ARM_CPU_PART_MASK 0xff00fff0
>
> #define ARM_CPU_XSCALE_ARCH_MASK 0xe000
> #define ARM_CPU_XSCALE_ARCH_V1 0x2000
> @@ -179,7 +180,7 @@ static inline unsigned int __attribute_const__ read_cpuid_implementor(void)
> */
> static inline unsigned int __attribute_const__ read_cpuid_part(void)
> {
> - return read_cpuid_id() & 0xff00fff0;
> + return read_cpuid_id() & ARM_CPU_PART_MASK;
> }
>
> static inline unsigned int __attribute_const__ __deprecated read_cpuid_part_number(void)
> diff --git a/arch/arm/include/asm/smp_plat.h b/arch/arm/include/asm/smp_plat.h
> index a252c0b..0ad7d49 100644
> --- a/arch/arm/include/asm/smp_plat.h
> +++ b/arch/arm/include/asm/smp_plat.h
> @@ -8,6 +8,7 @@
> #include <linux/cpumask.h>
> #include <linux/err.h>
>
> +#include <asm/cpu.h>
> #include <asm/cputype.h>
>
> /*
> @@ -25,6 +26,20 @@ static inline bool is_smp(void)
> #endif
> }
>
> +/**
> + * smp_cpuid_part() - return part id for a given cpu
> + * @cpu: logical cpu id.
> + *
> + * Return: part id of logical cpu passed as argument.
> + */
> +static inline unsigned int smp_cpuid_part(int cpu)
> +{
> + struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpu);
> +
> + return is_smp() ? cpu_info->cpuid & ARM_CPU_PART_MASK :
> + read_cpuid_part();
> +}
> +
> /* all SMP configurations have the extended CPUID registers */
> #ifndef CONFIG_MMU
> #define tlb_ops_need_broadcast() 0
> diff --git a/drivers/cpuidle/cpuidle-big_little.c b/drivers/cpuidle/cpuidle-big_little.c
> index 344d79fa..ef94c3b 100644
> --- a/drivers/cpuidle/cpuidle-big_little.c
> +++ b/drivers/cpuidle/cpuidle-big_little.c
> @@ -138,25 +138,18 @@ static int bl_enter_powerdown(struct cpuidle_device *dev,
> return idx;
> }
>
> -static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int cpu_id)
> +static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int part_id)
> {
> - struct cpuinfo_arm *cpu_info;
> struct cpumask *cpumask;
> - unsigned long cpuid;
> int cpu;
>
> cpumask = kzalloc(cpumask_size(), GFP_KERNEL);
> if (!cpumask)
> return -ENOMEM;
>
> - for_each_possible_cpu(cpu) {
> - cpu_info = &per_cpu(cpu_data, cpu);
> - cpuid = is_smp() ? cpu_info->cpuid : read_cpuid_id();
> -
> - /* read cpu id part number */
> - if ((cpuid & 0xFFF0) == cpu_id)
> + for_each_possible_cpu(cpu)
> + if (smp_cpuid_part(cpu) == part_id)
> cpumask_set_cpu(cpu, cpumask);
> - }
>
> drv->cpumask = cpumask;
>
> --
> 2.0.4
--
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