irqchip/apple-aic: Fix irq_disable from within irq handlers

[ Upstream commit 60a1cd10b222e004f860d14651e80089c77e8e6b ]

When disable_irq_nosync for an interrupt is called from within its
interrupt handler, this interrupt is only marked as disabled with the
intention to mask it when it triggers again.
The AIC hardware however automatically masks the interrupt when it is read.
aic_irq_eoi then unmasks it again if it's not disabled *and* not masked.
This results in a state mismatch between the hardware state and the
state kept in irq_data: The hardware interrupt is masked but
IRQD_IRQ_MASKED is not set. Any further calls to unmask_irq will directly
return and the interrupt can never be enabled again.

Fix this by keeping the hardware and irq_data state in sync by unmasking in
aic_irq_eoi if and only if the irq_data state also assumes the interrupt to
be unmasked.

Fixes: 76cde2639411 ("irqchip/apple-aic: Add support for the Apple Interrupt Controller")
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Acked-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210812100942.17206-1-sven@svenpeter.dev
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
index c179e27062fd52baffb2edca3bac25bd2e2ab349..151aab408fa6523b280519e4175c57e84bdae6fd 100644 (file)
--- a/drivers/irqchip/irq-apple-aic.c
+++ b/drivers/irqchip/irq-apple-aic.c
@@ -225,7 +225,7 @@ static void aic_irq_eoi(struct irq_data *d)
         * Reading the interrupt reason automatically acknowledges and masks
         * the IRQ, so we just unmask it here if needed.
         */
-       if (!irqd_irq_disabled(d) && !irqd_irq_masked(d))
+       if (!irqd_irq_masked(d))
                aic_irq_unmask(d);
 }