From: Doug Berger <opendmb@xxxxxxxxx> It was observed on Broadcom devices that use GIC v3 architecture L1 interrupt controllers as the parent of brcmstb-l2 interrupt controllers that the deactivation of the parent irq could happen before the brcmstb-l2 deasserted its output. This would lead the GIC to reactivate the irq only to find that no L2 interrupt was pending. The result was a spurious interrupt invoking the handle_bad_irq() with its associated messaging. While this did not create a functional problem it is a waste of cycles. The hazard exists because the memory mapped bus writes to the brcmstb-l2 registers are buffered and the GIC v3 architecture uses a very efficient system register write to deactivate the interrupt. This commit adds a write memory barrier prior to invoking chained_irq_exit() to introduce a dsb(st) on those systems to ensure the system register write cannot be executed until the memory mapped writes are visible to the system. Signed-off-by: Doug Berger <opendmb@xxxxxxxxx> Acked-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx> Fixes: 7f646e92766e ("irqchip: brcmstb-l2: Add Broadcom Set Top Box Level-2 interrupt controller") [florian: Added Fixes tag] Signed-off-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx> --- Changes in v2: - add Fixes tag - bump copyright drivers/irqchip/irq-brcmstb-l2.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/irqchip/irq-brcmstb-l2.c b/drivers/irqchip/irq-brcmstb-l2.c index 5559c943f03f..63aed60dd3f1 100644 --- a/drivers/irqchip/irq-brcmstb-l2.c +++ b/drivers/irqchip/irq-brcmstb-l2.c @@ -2,7 +2,7 @@ /* * Generic Broadcom Set Top Box Level 2 Interrupt controller driver * - * Copyright (C) 2014-2017 Broadcom + * Copyright (C) 2014-2024 Broadcom */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt @@ -112,6 +112,9 @@ static void brcmstb_l2_intc_irq_handle(struct irq_desc *desc) generic_handle_domain_irq(b->domain, irq); } while (status); out: + /* Don't ack parent before all device writes are done */ + wmb(); + chained_irq_exit(chip, desc); } -- 2.34.1