Re: [PATCH v2] sparc: Use generic idle loop

[Thomas Gleixner <tglx@linutronix.de>]

On Thu, 11 Apr 2013, Sam Ravnborg wrote:

> Add generic cpu_idle support
> 
> sparc32:
> - replace call to cpu_idle() with cpu_startup_entry()
> - add arch_cpu_idle()
> 
> sparc64:
> - smp_callin() now include cpu_startup_entry() call so we can
>   skip calling cpu_idle from assembler
> - add arch_cpu_idle() and arch_cpu_idle_dead()

Nice !

If Dave acks it, I'll pick it up 

Thanks,

	tglx

 
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Reviewed-by: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
> Cc: David S. Miller <davem@davemloft.net>
> ---
> v1->v2:
> - simplified arch_cpu_idle() - former sparc64_yield() based on comments from Srivatsa
> - dropped TIF_POLLING_NRFLAG handling
> - dropped smp_mb__after_clear_bit() - this is done in generic code using rmb()
> - dropped the out-most while (!need_resched() && !cpu_is_offline(cpu))
> - always enable irq on exit in arch_cpu_idle (both sparc32 and sparc64)
> - added comment from davem why we need to clear IE bit in sparc64 arch_cpu_idle()
> 
> 	Sam
> 
> 
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 3d361f2..ee5eacc 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -37,6 +37,7 @@ config SPARC
>  	select GENERIC_SMP_IDLE_THREAD
>  	select GENERIC_CMOS_UPDATE
>  	select GENERIC_CLOCKEVENTS
> +	select GENERIC_IDLE_LOOP
>  	select GENERIC_STRNCPY_FROM_USER
>  	select GENERIC_STRNLEN_USER
>  	select MODULES_USE_ELF_RELA
> diff --git a/arch/sparc/kernel/hvtramp.S b/arch/sparc/kernel/hvtramp.S
> index 9365432..605c960 100644
> --- a/arch/sparc/kernel/hvtramp.S
> +++ b/arch/sparc/kernel/hvtramp.S
> @@ -128,8 +128,7 @@ hv_cpu_startup:
>  
>  	call		smp_callin
>  	 nop
> -	call		cpu_idle
> -	 mov		0, %o0
> +
>  	call		cpu_panic
>  	 nop
>  
> diff --git a/arch/sparc/kernel/process_32.c b/arch/sparc/kernel/process_32.c
> index 62eede1..c852410 100644
> --- a/arch/sparc/kernel/process_32.c
> +++ b/arch/sparc/kernel/process_32.c
> @@ -64,23 +64,12 @@ extern void fpsave(unsigned long *, unsigned long *, void *, unsigned long *);
>  struct task_struct *last_task_used_math = NULL;
>  struct thread_info *current_set[NR_CPUS];
>  
> -/*
> - * the idle loop on a Sparc... ;)
> - */
> -void cpu_idle(void)
> +/* Idle loop support. */
> +void arch_cpu_idle(void)
>  {
> -	set_thread_flag(TIF_POLLING_NRFLAG);
> -
> -	/* endless idle loop with no priority at all */
> -	for (;;) {
> -		while (!need_resched()) {
> -			if (sparc_idle)
> -				(*sparc_idle)();
> -			else
> -				cpu_relax();
> -		}
> -		schedule_preempt_disabled();
> -	}
> +	if (sparc_idle)
> +		(*sparc_idle)();
> +	local_irq_enable();
>  }
>  
>  /* XXX cli/sti -> local_irq_xxx here, check this works once SMP is fixed. */
> diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
> index cdb80b2..9fbf0d1 100644
> --- a/arch/sparc/kernel/process_64.c
> +++ b/arch/sparc/kernel/process_64.c
> @@ -52,20 +52,17 @@
>  
>  #include "kstack.h"
>  
> -static void sparc64_yield(int cpu)
> +/* Idle loop support on sparc64. */
> +void arch_cpu_idle(void)
>  {
>  	if (tlb_type != hypervisor) {
>  		touch_nmi_watchdog();
> -		return;
> -	}
> -
> -	clear_thread_flag(TIF_POLLING_NRFLAG);
> -	smp_mb__after_clear_bit();
> -
> -	while (!need_resched() && !cpu_is_offline(cpu)) {
> +	} else {
>  		unsigned long pstate;
>  
> -		/* Disable interrupts. */
> +                /* The sun4v sleeping code requires that we have PSTATE.IE cleared over
> +                 * the cpu sleep hypervisor call.
> +                 */
>  		__asm__ __volatile__(
>  			"rdpr %%pstate, %0\n\t"
>  			"andn %0, %1, %0\n\t"
> @@ -73,7 +70,7 @@ static void sparc64_yield(int cpu)
>  			: "=&r" (pstate)
>  			: "i" (PSTATE_IE));
>  
> -		if (!need_resched() && !cpu_is_offline(cpu))
> +		if (!need_resched() && !cpu_is_offline(smp_processor_id()))
>  			sun4v_cpu_yield();
>  
>  		/* Re-enable interrupts. */
> @@ -84,36 +81,16 @@ static void sparc64_yield(int cpu)
>  			: "=&r" (pstate)
>  			: "i" (PSTATE_IE));
>  	}
> -
> -	set_thread_flag(TIF_POLLING_NRFLAG);
> +	local_irq_enable();
>  }
>  
> -/* The idle loop on sparc64. */
> -void cpu_idle(void)
> -{
> -	int cpu = smp_processor_id();
> -
> -	set_thread_flag(TIF_POLLING_NRFLAG);
> -
> -	while(1) {
> -		tick_nohz_idle_enter();
> -		rcu_idle_enter();
> -
> -		while (!need_resched() && !cpu_is_offline(cpu))
> -			sparc64_yield(cpu);
> -
> -		rcu_idle_exit();
> -		tick_nohz_idle_exit();
> -
>  #ifdef CONFIG_HOTPLUG_CPU
> -		if (cpu_is_offline(cpu)) {
> -			sched_preempt_enable_no_resched();
> -			cpu_play_dead();
> -		}
> -#endif
> -		schedule_preempt_disabled();
> -	}
> +void arch_cpu_idle_dead()
> +{
> +	sched_preempt_enable_no_resched();
> +	cpu_play_dead();
>  }
> +#endif
>  
>  #ifdef CONFIG_COMPAT
>  static void show_regwindow32(struct pt_regs *regs)
> diff --git a/arch/sparc/kernel/smp_32.c b/arch/sparc/kernel/smp_32.c
> index 9e7e6d7..e3f2b81 100644
> --- a/arch/sparc/kernel/smp_32.c
> +++ b/arch/sparc/kernel/smp_32.c
> @@ -369,7 +369,7 @@ void __cpuinit sparc_start_secondary(void *arg)
>  	local_irq_enable();
>  
>  	wmb();
> -	cpu_idle();
> +	cpu_startup_entry(CPUHP_ONLINE);
>  
>  	/* We should never reach here! */
>  	BUG();
> diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
> index 537eb66..c025ffc 100644
> --- a/arch/sparc/kernel/smp_64.c
> +++ b/arch/sparc/kernel/smp_64.c
> @@ -127,6 +127,8 @@ void __cpuinit smp_callin(void)
>  
>  	/* idle thread is expected to have preempt disabled */
>  	preempt_disable();
> +
> +	cpu_startup_entry(CPUHP_ONLINE);
>  }
>  
>  void cpu_panic(void)
> diff --git a/arch/sparc/kernel/trampoline_64.S b/arch/sparc/kernel/trampoline_64.S
> index da1b781..2e973a2 100644
> --- a/arch/sparc/kernel/trampoline_64.S
> +++ b/arch/sparc/kernel/trampoline_64.S
> @@ -407,8 +407,7 @@ after_lock_tlb:
>  
>  	call		smp_callin
>  	 nop
> -	call		cpu_idle
> -	 mov		0, %o0
> +
>  	call		cpu_panic
>  	 nop
>  1:	b,a,pt		%xcc, 1b
>