[PATCH v3 4/6] irqchip: sifive-plic: Add warning in plic_init() if handler already present

[Anup Patel]

We have two enteries (one for M-mode and another for S-mode) in the
interrupts-extended DT property of PLIC DT node for each HART. It is
expected that firmware/bootloader will set M-mode HWIRQ line of each
HART to 0xffffffff (i.e. -1) in interrupts-extended DT property
because Linux runs in S-mode only.

If firmware/bootloader is buggy then it will not correctly update
interrupts-extended DT property which might result in a plic_handler
configured twice. This patch adds a warning in plic_init() if a
plic_handler is already marked present. This warning provides us
a hint about incorrectly updated interrupts-extended DT property.

Signed-off-by: Anup Patel <anup@xxxxxxxxxxxxxx>
---
 drivers/irqchip/irq-sifive-plic.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index d4433399eb89..3d4f205f8abe 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -234,6 +234,11 @@ static int __init plic_init(struct device_node *node,
 
 		cpu = riscv_hartid_to_cpuid(hartid);
 		handler = per_cpu_ptr(&plic_handlers, cpu);
+		if (handler->present) {
+			pr_warn("handler not available for context %d.\n", i);
+			continue;
+		}
+
 		handler->present = true;
 		handler->hart_base =
 			plic.regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
-- 
2.17.1