Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 21 Jan 2021 13:44:17 +0100 | Subject | Re: [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver. |
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On Wed, Jan 20, 2021 at 2:27 PM Mohamed Mediouni <mohamed.mediouni@caramail.com> wrote:
> +#ifdef CONFIG_SMP > +static void apple_aic_ipi_send_mask(struct irq_data *d, > + const struct cpumask *mask)
Not sure we care about the #ifdef here, given that arch/arm64 does not allow building a kernel without CONFIG_SMP.
> + /* > + * Ensure that stores to Normal memory are visible to the > + * other CPUs before issuing the IPI. > + */ > + wmb(); > + > + for_each_cpu (cpu, mask) { > + smp_mb__before_atomic(); > + atomic_or(1u << irqnr, per_cpu_ptr(&aic_ipi_mask, cpu)); > + smp_mb__after_atomic(); > + lcpu = get_cpu(); > + if (aic.fast_ipi) { > + if ((lcpu >> 2) == (cpu >> 2)) > + write_sysreg(cpu & 3, SR_APPLE_IPI_LOCAL); > + else > + write_sysreg((cpu & 3) | ((cpu >> 2) << 16), > + SR_APPLE_IPI_REMOTE); > + } else > + writel(lcpu == cpu ? REG_IPI_FLAG_SELF : > + (REG_IPI_FLAG_OTHER << cpu), > + aic.base + REG_IPI_SET); > + put_cpu(); > + } > + > + /* Force the above writes to be executed */ > + if (aic.fast_ipi) > + isb(); > +}
Since this just loops over all CPUs, I'd probably just turn it into an ipi_send_single() callback and have the caller do the loop for simplicity.
I also have the feeling that splitting one hardware IPI into multiple logical interrupts, which are then all registered by the same irq handler adds a little more complexity than necessary.
Changing this would of course require modifications to arch/arm64/kernel/smp.c, which is hardwired to use CONFIG_GENERIC_IRQ_IPI in smp_cross_call(), and allowing a different code path there may be worse than emulating an irqchip.
> @@ -186,8 +325,11 @@ static int __init apple_aic_init(struct device_node *node, > if (WARN(!aic.base, "unable to map aic registers\n")) > return -EINVAL; > > + aic.fast_ipi = of_property_read_bool(node, "fast-ipi");
Where is this property documented, and what decides which one to use?
Arnd
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