Re: [PATCH v4 04/14] irqchip: mips-gic: Support multi-cluster in for_each_online_cpu_gic()

[Thomas Gleixner]

On Sat, May 11 2024 at 12:43, Aleksandar Rikalo wrote:
> From: Paul Burton <paulburton@xxxxxxxxxx>
>
> Introduce support for multi-cluster GIC register access in
> __gic_with_next_online_cpu(), and therefore in its user
> for_each_online_cpu_gic(). We access registers in remote clusters
> using the CM's GCR_CL_REDIRECT register, and so here we delegate
> to mips_cm_lock_other() in order to configure this access.

Again: We do nothing. See docs.

> @@ -70,6 +70,20 @@ static int __gic_with_next_online_cpu(int prev)
>  {
>  	unsigned int cpu;
>  
> +	/*
> +	 * Unlock access to the previous CPU's GIC local register block.
> +	 *
> +	 * Delegate to the CM locking code in the multi-cluster case, since
> +	 * other clusters can only be accessed using GCR_CL_REDIRECT.
> +	 *
> +	 * In the single cluster case we don't need to do anything; the caller
> +	 * is responsible for maintaining gic_lock & nothing should be
> +	 * expecting any particular value of GIC_VL_OTHER so we can leave it
> +	 * as-is.
> +	 */
> +	if ((prev != -1) && mips_cps_multicluster_cpus())
> +		mips_cm_unlock_other();

Eew.

static inline void gic_unlock_cluster(void)
{
	if (mips_cps_multicluster_cpus())
		mips_cm_unlock_other();
}

#define for_each_online_cpu_gic(cpu, gic_lock)		\
	guard(raw_spinlock_irqsave)(gic_lock);		\
	for ((cpu) = __gic_with_next_online_cpu(-1);	\
	     (cpu) < nr_cpu_ids;			\
             gic_unlock_cluster(),			\
	     (cpu) = __gic_with_next_online_cpu(cpu);)

No?

Thanks,

        tglx