openwrtv4/target/linux/brcm2708/patches-4.4/0005-irq-bcm2836-Prevent-spurious-interrupts-and-trap-the.patch

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From 38395f1ae1258743c3e0081c86bb4b65ad06dd69 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Fri, 4 Dec 2015 17:41:50 +0000
Subject: [PATCH 005/127] irq-bcm2836: Prevent spurious interrupts, and trap
them early
The old arch-specific IRQ macros included a dsb to ensure the
write to clear the mailbox interrupt completed before returning
from the interrupt. The BCM2836 irqchip driver needs the same
precaution to avoid spurious interrupts.
Spurious interrupts are still possible for other reasons,
though, so trap them early.
---
drivers/irqchip/irq-bcm2836.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/irqchip/irq-bcm2836.c
+++ b/drivers/irqchip/irq-bcm2836.c
@@ -170,9 +170,10 @@ __exception_irq_entry bcm2836_arm_irqchi
u32 ipi = ffs(mbox_val) - 1;
writel(1 << ipi, mailbox0);
+ dsb();
handle_IPI(ipi, regs);
#endif
- } else {
+ } else if (stat) {
u32 hwirq = ffs(stat) - 1;
handle_IRQ(irq_linear_revmap(intc.domain, hwirq), regs);