[PATCH 1/4] irqchip/sifive-plic: Setup cpuhp once after current handler is present

[Anup Patel]

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.

Signed-off-by: Anup Patel <anup.pa...@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 822e074c0600..7dc23edb3267 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,
@@ -282,6 +283,7 @@ 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)
@@ -310,7 +312,6 @@ 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;
 
@@ -364,9 +365,18 @@ 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;
+       }
+
        pr_info("mapped %d interrupts with %d handlers for %d contexts.\n",
                nr_irqs, nr_handlers, nr_contexts);
        set_handle_irq(plic_handle_irq);
-- 
2.25.1