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Subject[PATCH v6 2/4] irqchip: sifive-plic: Add warning in plic_init() if handler already present
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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>
---
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 c23a293a2aae..da09f46fad64 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -229,6 +229,11 @@ 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 already present for context %d.\n", i);
+ continue;
+ }
+
handler->present = true;
handler->hart_base =
plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
--
2.17.1
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