Subject: Re: [PATCH 2/7] powerpc/85xx: add HOTPLUG_CPU support

From: Benjamin Herrenschmidt <[email-masked]>
Date: Fri, 11 Nov 2011 15:22:56 +1100

On Fri, 2011-11-04 at 20:31 +0800, Zhao Chenhui wrote:

>  #ifdef CONFIG_SMP
>  /* When we get here, r24 needs to hold the CPU # */
>  	.globl __secondary_start
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 7bf2187..12a54f0 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -381,8 +381,14 @@ void generic_cpu_die(unsigned int cpu)
>  
>  	for (i = 0; i < 100; i++) {
>  		smp_rmb();
> -		if (per_cpu(cpu_state, cpu) == CPU_DEAD)
> +		if (per_cpu(cpu_state, cpu) == CPU_DEAD) {
> +			/*
> +			 * After another core sets cpu_state to CPU_DEAD,
> +			 * it needs some time to die.
> +			 */
> +			msleep(10);
>  			return;
> +		}
>  		msleep(100);
>  	}
>  	printk(KERN_ERR "CPU%d didn't die...\n", cpu);

I don't really see why you need to wait. This loop is about waiting for
the CPU to mark itself DEAD, not necessarily to be physically powered
off.

> +struct epapr_entry {
> +	u32	addr_h;
> +	u32	addr_l;
> +	u32	r3_h;
> +	u32	r3_l;
> +	u32	reserved;
> +	u32	pir;
> +	u32	r6_h;
> +	u32	r6_l;
> +};

This should probably be in a generic location.

> +static int is_corenet;

This global is a bit gross...

 ...

> +
> +static void __cpuinit smp_85xx_reset_core(int nr)
> +{
> +	__iomem u32 *vaddr, *pir_vaddr;
> +	u32 val, cpu_mask;
> +
> +	/* If CoreNet platform, use BRR as release register. */
> +	if (is_corenet) {
> +		cpu_mask = 1 << nr;
> +		vaddr = ioremap(get_immrbase() + MPC85xx_BRR_OFF, 4);
> +	} else {
> +		cpu_mask = 1 << (24 + nr);
> +		vaddr = ioremap(get_immrbase() + MPC85xx_ECM_EEBPCR_OFF, 4);
> +	}

Instead, can't you instead have two functions using a common helper and
pick/hook the right one ?

Also in what context is that reset_core() called ? Doing ioremap isn't
something you can do at any random time...

Cheers,
Ben.