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SubjectRe: [PATCH v2 2/3] irqchip/sifive-plic: Setup cpuhp once after boot CPU handler is present
On Fri, May 22, 2020 at 3:36 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Mon, 18 May 2020 02:14:40 PDT (-0700), Anup Patel wrote:
> > For multiple PLIC instances, the plic_init() is called once for each
> > PLIC instance. Due to this we have two issues:
> > 1. cpuhp_setup_state() is called multiple times
> > 2. plic_starting_cpu() can crash for boot CPU if cpuhp_setup_state()
> > is called before boot CPU PLIC handler is available.
> >
> > This patch fixes both above issues.
> >
> > Fixes: f1ad1133b18f ("irqchip/sifive-plic: Add support for multiple PLICs")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Anup Patel <anup.patel@wdc.com>
> > ---
> > drivers/irqchip/irq-sifive-plic.c | 14 ++++++++++++--
> > 1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> > index 9f7f8ce88c00..6c54abf5cc5e 100644
> > --- a/drivers/irqchip/irq-sifive-plic.c
> > +++ b/drivers/irqchip/irq-sifive-plic.c
> > @@ -76,6 +76,7 @@ struct plic_handler {
> > void __iomem *enable_base;
> > struct plic_priv *priv;
> > };
> > +static bool plic_cpuhp_setup_done;
> > static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
> >
> > static inline void plic_toggle(struct plic_handler *handler,
> > @@ -285,6 +286,7 @@ static int __init plic_init(struct device_node *node,
> > int error = 0, nr_contexts, nr_handlers = 0, i;
> > u32 nr_irqs;
> > struct plic_priv *priv;
> > + struct plic_handler *handler;
> >
> > priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> > if (!priv)
> > @@ -313,7 +315,6 @@ static int __init plic_init(struct device_node *node,
> >
> > for (i = 0; i < nr_contexts; i++) {
> > struct of_phandle_args parent;
> > - struct plic_handler *handler;
> > irq_hw_number_t hwirq;
> > int cpu, hartid;
> >
> > @@ -367,9 +368,18 @@ static int __init plic_init(struct device_node *node,
> > nr_handlers++;
> > }
> >
> > - cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
> > + /*
> > + * We can have multiple PLIC instances so setup cpuhp state only
> > + * when context handler for current/boot CPU is present.
> > + */
> > + handler = this_cpu_ptr(&plic_handlers);
> > + if (handler->present && !plic_cpuhp_setup_done) {
> > + cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
> > "irqchip/sifive/plic:starting",
> > plic_starting_cpu, plic_dying_cpu);
> > + plic_cpuhp_setup_done = true;
>
> So presumably something else is preventing multiple plic_init() calls from
> executing at the same time? Assuming that's the case

AFAIK, interrupt controller and timer probing happens sequentially on
boot CPU before all secondary CPUs are brought-up.

>
> Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
> Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
>
> > + }
> > +
> > pr_info("mapped %d interrupts with %d handlers for %d contexts.\n",
> > nr_irqs, nr_handlers, nr_contexts);
> > set_handle_irq(plic_handle_irq);

Thanks,
Anup

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