irqchip/sifive-plic: Add warning in plic_init() if handler already present

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@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index 715ef7b3f42d33a3e5f358f4c34c745fda63e031..b8721b4f8b2fc5fc04b2a8c3adba4ac88a3b8195 100644 (file)
--- 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,
                }
 
                handler = per_cpu_ptr(&plic_handlers, cpu);
+               if (handler->present) {
+                       pr_warn("handler already present for context %d.\n", i);
+                       continue;
+               }
+
                handler->present = true;
                handler->hart_base =
                        plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;