Date:	Sat, 02 Jun 2012 21:28:35 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Sam Ravnborg <sam@...nborg.org>
CC:	David Miller <davem@...emloft.net>, tglx@...utronix.de,
	peterz@...radead.org, paulmck@...ux.vnet.ibm.com,
	rusty@...tcorp.com.au, mingo@...nel.org, yong.zhang0@...il.com,
	akpm@...ux-foundation.org, vatsa@...ux.vnet.ibm.com, rjw@...k.pl,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	nikunj@...ux.vnet.ibm.com, vapier@...too.org, konrad@...sler.com,
	tkhai@...dex.ru, sparclinux@...r.kernel.org
Subject: Re: [UPDATED PATCH 21/27] sparc32, smpboot: Use generic SMP booting
 infrastructure

On 06/02/2012 08:43 PM, Sam Ravnborg wrote:

>>
>>> I will try to dive into this and see if I on the sparc32 side
>>> can make leon behave like the other platforms, and then 
>>> unify some of the smp cpu boot stuff such that we then
>>> can introduce the generalization from your patch.
> 
> This is what I came up with.
> I modelled this over your patch-set to make it
> simpler to convert to the generic scheme.
> 


Thanks a lot for doing this :-)

> I realised a bit more how CPU's are started up on sparc32.
> So I think all of leon, sun4m and sun4d should work with this.
> 
> But my SUN box is defunct atm. so I have not tested it.
> Comments appreciated!
> 
> PS. I used the ugly __names for now.
> As soon as you have found a better set of names this should
> be fixed here too.
>


As I mentioned in my other mail, I am thinking of changing them to
arch_cpu_pre_starting(), arch_cpu_pre_online() and arch_cpu_post_online().
Let me know what you think of those names.

Would you kindly add a changelog and your sign-off to this patch?

> 
> diff --git a/arch/sparc/kernel/kernel.h b/arch/sparc/kernel/kernel.h
> index 291bb5d..2bc1c6d 100644
> --- a/arch/sparc/kernel/kernel.h
> +++ b/arch/sparc/kernel/kernel.h
> @@ -48,6 +48,10 @@ extern void sun4m_init_IRQ(void);
>  extern void sun4m_unmask_profile_irq(void);
>  extern void sun4m_clear_profile_irq(int cpu);
> 
> +/* sun4m_smp.c */
> +void sun4m_cpu_pre_starting(void);
> +void sun4m_cpu_pre_online(void);
> +
>  /* sun4d_irq.c */
>  extern spinlock_t sun4d_imsk_lock;
> 
> @@ -60,6 +64,14 @@ extern int show_sun4d_interrupts(struct seq_file *, void *);
>  extern void sun4d_distribute_irqs(void);
>  extern void sun4d_free_irq(unsigned int irq, void *dev_id);
> 
> +/* sun4d_smp.c */
> +void sun4d_cpu_pre_starting(void);
> +void sun4d_cpu_pre_online(void);
> +
> +/* leon_smp.c */
> +void leon_cpu_pre_starting(void);
> +void leon_cpu_pre_online(void);
> +
>  /* head_32.S */
>  extern unsigned int t_nmi[];
>  extern unsigned int linux_trap_ipi15_sun4d[];
> diff --git a/arch/sparc/kernel/leon_smp.c b/arch/sparc/kernel/leon_smp.c
> index 0f3fb6d..0b028b3 100644
> --- a/arch/sparc/kernel/leon_smp.c
> +++ b/arch/sparc/kernel/leon_smp.c
> @@ -69,31 +69,20 @@ static inline unsigned long do_swap(volatile unsigned long *ptr,
>  	return val;
>  }
> 
> -void __cpuinit leon_callin(void)
> +void __cpuinit leon_cpu_pre_starting(void)
>  {
> -	int cpuid = hard_smp_processor_id();
> -
> -	local_ops->cache_all();
> -	local_ops->tlb_all();
>  	leon_configure_cache_smp();
> +}
> 
> -	notify_cpu_starting(cpuid);
> -
> -	/* Get our local ticker going. */
> -	register_percpu_ce(cpuid);
> -
> -	calibrate_delay();
> -	smp_store_cpu_info(cpuid);
> 
> -	local_ops->cache_all();
> -	local_ops->tlb_all();
> +void __cpuinit cpu_cpu_pre_starting(void *unused)


Shouldn't this be leon_cpu_pre_online()? And the parameters
should be consistent too (here it expects a void*, but it is
called with no arguments...)

> +{
> +	int cpuid = hard_smp_processor_id();
> 
> -	/*
> -	 * Unblock the master CPU _only_ when the scheduler state
> -	 * of all secondary CPUs will be up-to-date, so after
> -	 * the SMP initialization the master will be just allowed
> -	 * to call the scheduler code.
> -	 * Allow master to continue.
> +	/* Allow master to continue. The master will then give us the
> +	 * go-ahead by setting the smp_commenced_mask and will wait without
> +	 * timeouts until our setup is completed fully (signified by
> +	 * our bit being set in the cpu_online_mask).
>  	 */
>  	do_swap(&cpu_callin_map[cpuid], 1);
> 
> @@ -110,9 +99,6 @@ void __cpuinit leon_callin(void)
> 
>  	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
>  		mb();
> -
> -	local_irq_enable();
> -	set_cpu_online(cpuid, true);
>  }
> 
>  /*
> diff --git a/arch/sparc/kernel/smp_32.c b/arch/sparc/kernel/smp_32.c
> index 79db45e..2e2990f 100644
> --- a/arch/sparc/kernel/smp_32.c
> +++ b/arch/sparc/kernel/smp_32.c
> @@ -20,6 +20,7 @@
>  #include <linux/seq_file.h>
>  #include <linux/cache.h>
>  #include <linux/delay.h>
> +#include <linux/cpu.h>
> 
>  #include <asm/ptrace.h>
>  #include <linux/atomic.h>
> @@ -32,8 +33,10 @@
>  #include <asm/cacheflush.h>
>  #include <asm/tlbflush.h>
>  #include <asm/cpudata.h>
> +#include <asm/timer.h>
>  #include <asm/leon.h>
> 
> +#include "kernel.h"
>  #include "irq.h"
> 
>  volatile unsigned long cpu_callin_map[NR_CPUS] __cpuinitdata = {0,};
> @@ -294,6 +297,89 @@ int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *tidle)
>  	return ret;
>  }
> 
> +void __cpuinit __cpu_pre_starting(void *unused)
> +{
> +	local_ops->cache_all();
> +	local_ops->tlb_all();
> +
> +	switch(sparc_cpu_model) {
> +	case sun4m:
> +		sun4m_cpu_pre_starting();


Wouldn't it be better to have a provision to pass the
pointer down to these functions as well?

> +		break;
> +	case sun4d:
> +		sun4d_cpu_pre_starting();
> +		break;
> +	case sparc_leon:
> +		leon_cpu_pre_starting();
> +		break;
> +	default:
> +		BUG();
> +	}
> +}
> +
> +void __cpuinit __cpu_pre_online(void *unused)
> +{
> +	unsigned int cpuid = hard_smp_processor_id();
> +
> +	register_percpu_ce(cpuid);
> +
> +	calibrate_delay();
> +	smp_store_cpu_info(cpuid);
> +
> +	local_ops->cache_all();
> +	local_ops->tlb_all();
> +
> +	switch(sparc_cpu_model) {
> +	case sun4m:
> +		sun4m_cpu_pre_online();
> +		break;
> +	case sun4d:
> +		sun4d_cpu_pre_online();
> +		break;
> +	case sparc_leon:
> +		leon_cpu_pre_starting();


Shouldn't this be leon_cpu_pre_online()?

> +		break;
> +	default:
> +		BUG();
> +	}
> +}
> +
> +void __cpuinit sparc_start_secondary(void *unused)
> +{
> +	unsigned int cpu;
> +
> +	/*
> +	 * SMP booting is extremely fragile in some architectures. So run
> +	 * the cpu initialization code first before anything else.
> +	 */
> +	__cpu_pre_starting(NULL);
> +


Why not pass the pointer to __cpu_pre_starting() as well as the rest of
the functions?

> +	preempt_disable();
> +	cpu = smp_processor_id();
> +
> +	/* Invoke the CPU_STARTING notifier callbacks */
> +	notify_cpu_starting(cpu);
> +
> +	__cpu_pre_online(NULL);
> +
> +	/* Set the CPU in the cpu_online_mask */
> +	set_cpu_online(cpu, true);
> +
> +	/* Enable local interrupts now */
> +	local_irq_enable();
> +
> +	wmb();
> +	cpu_idle();
> +
> +	/* We should never reach here! */
> +	BUG();
> +}
> +
> +void __cpuinit smp_callin(void)
> +{
> +	sparc_start_secondary(NULL);
> +}
> +
>  void smp_bogo(struct seq_file *m)
>  {
>  	int i;
> diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
> index ddaea31..bfbbc46 100644
> --- a/arch/sparc/kernel/sun4d_smp.c
> +++ b/arch/sparc/kernel/sun4d_smp.c
> @@ -50,10 +50,9 @@ static inline void show_leds(int cpuid)
>  			      "i" (ASI_M_CTL));
>  }
> 
> -void __cpuinit smp4d_callin(void)
> +void __cpuinit sun4d_cpu_pre_starting(void)
>  {
>  	int cpuid = hard_smp_processor_id();
> -	unsigned long flags;
> 
>  	/* Show we are alive */
>  	cpu_leds[cpuid] = 0x6;
> @@ -61,24 +60,14 @@ void __cpuinit smp4d_callin(void)
> 
>  	/* Enable level15 interrupt, disable level14 interrupt for now */
>  	cc_set_imsk((cc_get_imsk() & ~0x8000) | 0x4000);
> +}
> 
> -	local_ops->cache_all();
> -	local_ops->tlb_all();
> -
> -	notify_cpu_starting(cpuid);
> -	/*
> -	 * Unblock the master CPU _only_ when the scheduler state
> -	 * of all secondary CPUs will be up-to-date, so after
> -	 * the SMP initialization the master will be just allowed
> -	 * to call the scheduler code.
> -	 */
> -	/* Get our local ticker going. */
> -	register_percpu_ce(cpuid);
> +void __cpuinit sun4d_cpu_pre_online(void)
> +{
> +	unsigned long flags;
> +	int cpuid;
> 
> -	calibrate_delay();
> -	smp_store_cpu_info(cpuid);
> -	local_ops->cache_all();
> -	local_ops->tlb_all();
> +	cpuid = hard_smp_processor_id();
> 
>  	/* Allow master to continue. */
>  	sun4d_swap((unsigned long *)&cpu_callin_map[cpuid], 1);
> @@ -106,16 +95,12 @@ void __cpuinit smp4d_callin(void)
>  	local_ops->cache_all();
>  	local_ops->tlb_all();
> 
> -	local_irq_enable();	/* We don't allow PIL 14 yet */
> -
>  	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
>  		barrier();
> 
>  	spin_lock_irqsave(&sun4d_imsk_lock, flags);
>  	cc_set_imsk(cc_get_imsk() & ~0x4000); /* Allow PIL 14 as well */
>  	spin_unlock_irqrestore(&sun4d_imsk_lock, flags);
> -	set_cpu_online(cpuid, true);
> -
>  }
> 
>  /*
> diff --git a/arch/sparc/kernel/sun4m_smp.c b/arch/sparc/kernel/sun4m_smp.c
> index 128af73..0cf6b4f 100644
> --- a/arch/sparc/kernel/sun4m_smp.c
> +++ b/arch/sparc/kernel/sun4m_smp.c
> @@ -34,30 +34,19 @@ swap_ulong(volatile unsigned long *ptr, unsigned long val)
>  	return val;
>  }
> 
> -void __cpuinit smp4m_callin(void)
> +void __cpuinit sun4m_cpu_pre_starting(void)
>  {
> -	int cpuid = hard_smp_processor_id();
> -
> -	local_ops->cache_all();
> -	local_ops->tlb_all();
> -
> -	notify_cpu_starting(cpuid);
> -
> -	register_percpu_ce(cpuid);
> -
> -	calibrate_delay();
> -	smp_store_cpu_info(cpuid);
> +}
> 
> -	local_ops->cache_all();
> -	local_ops->tlb_all();
> +void __cpuinit sun4m_cpu_pre_online(void)
> +{
> +	int cpuid = hard_smp_processor_id();
> 
> -	/*
> -	 * Unblock the master CPU _only_ when the scheduler state
> -	 * of all secondary CPUs will be up-to-date, so after
> -	 * the SMP initialization the master will be just allowed
> -	 * to call the scheduler code.
> +	/* Allow master to continue. The master will then give us the
> +	 * go-ahead by setting the smp_commenced_mask and will wait without
> +	 * timeouts until our setup is completed fully (signified by
> +	 * our bit being set in the cpu_online_mask).
>  	 */
> -	/* Allow master to continue. */
>  	swap_ulong(&cpu_callin_map[cpuid], 1);
> 
>  	/* XXX: What's up with all the flushes? */
> @@ -75,10 +64,6 @@ void __cpuinit smp4m_callin(void)
> 
>  	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
>  		mb();
> -
> -	local_irq_enable();
> -
> -	set_cpu_online(cpuid, true);
>  }
> 
>  /*
> diff --git a/arch/sparc/kernel/trampoline_32.S b/arch/sparc/kernel/trampoline_32.S
> index af27aca..6cdb08c 100644
> --- a/arch/sparc/kernel/trampoline_32.S
> +++ b/arch/sparc/kernel/trampoline_32.S
> @@ -79,18 +79,15 @@ cpu3_startup:
>  	 nop
> 
>  	/* Start this processor. */
> -	call	smp4m_callin
> +	call	smp_callin
>  	 nop
> 
> -	b,a	smp_do_cpu_idle
> +	b,a	smp_panic
> 
>  	.text
>  	.align	4
> 
> -smp_do_cpu_idle:
> -	call	cpu_idle
> -	 mov	0, %o0
> -
> +smp_panic:
>  	call	cpu_panic
>  	 nop
> 
> @@ -144,10 +141,10 @@ sun4d_cpu_startup:
>  	 nop
> 
>  	/* Start this processor. */
> -	call	smp4d_callin
> +	call	smp_callin
>  	 nop
> 
> -	b,a	smp_do_cpu_idle
> +	b,a	smp_panic
> 
>  	__CPUINIT
>  	.align	4
> @@ -201,7 +198,7 @@ leon_smp_cpu_startup:
>  	 nop
> 
>  	/* Start this processor. */
> -	call	leon_callin
> +	call	smp_callin


I still didn't get how this solves the original problem of
not having sparc_cpu_model set to sparc_leon. You mentioned
that by the time we reach leon_smp_cpu_startup, that variable
is not set. Even inside leon_smp_cpu_startup, I don't immediately
see where it is set. Am I missing something?

>  	 nop
> 
> -	b,a	smp_do_cpu_idle
> +	b,a	smp_panic
> 


Regards,
Srivatsa S. Bhat

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