Re: [PATCH] cpuidle/cpuidle-big_little: fix reading cpu id part number

[Lorenzo Pieralisi]

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@xxxxxxx>
> 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@xxxxxxx>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> ---
>  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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