[PATCH 6.18 076/752] irqchip/riscv-imsic: Add a CPU pm notifier to restore the IMSIC on exit

Sasha Levin
2026-02-28T17:49:13Z

From: Nick Hu <nick.hu@sifive.com>

[ Upstream commit f48b4bd0915bf61ac12b8c65c7939ebd03bc8abf ]

The IMSIC might be reset when the system enters a low power state, but on
exit nothing restores the registers, which prevents interrupt delivery.

Solve this by registering a CPU power management notifier, which restores
the IMSIC on exit.

Signed-off-by: Nick Hu <nick.hu@sifive.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Cyan Yang <cyan.yang@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://patch.msgid.link/20251202-preserve-aplic-imsic-v3-1-1844fbf1fe92@sifive.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/irqchip/irq-riscv-imsic-early.c | 39 ++++++++++++++++++++-----
1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/drivers/irqchip/irq-riscv-imsic-early.c b/drivers/irqchip/irq-riscv-imsic-early.c
index 2c4c682627b8c..d1727c343c38f 100644
--- a/drivers/irqchip/irq-riscv-imsic-early.c
+++ b/drivers/irqchip/irq-riscv-imsic-early.c
@@ -7,6 +7,7 @@
#define pr_fmt(fmt) "riscv-imsic: " fmt
#include <linux/acpi.h>
#include <linux/cpu.h>
+#include <linux/cpu_pm.h>
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/init.h>
@@ -128,14 +129,8 @@ static void imsic_handle_irq(struct irq_desc *desc)
chained_irq_exit(chip, desc);
}

-static int imsic_starting_cpu(unsigned int cpu)
+static void imsic_hw_states_init(void)
{
- /* Mark per-CPU IMSIC state as online */
- imsic_state_online();
-
- /* Enable per-CPU parent interrupt */
- enable_percpu_irq(imsic_parent_irq, irq_get_trigger_type(imsic_parent_irq));
-
/* Setup IPIs */
imsic_ipi_starting_cpu();

@@ -147,6 +142,18 @@ static int imsic_starting_cpu(unsigned int cpu)

/* Enable local interrupt delivery */
imsic_local_delivery(true);
+}
+
+static int imsic_starting_cpu(unsigned int cpu)
+{
+ /* Mark per-CPU IMSIC state as online */
+ imsic_state_online();
+
+ /* Enable per-CPU parent interrupt */
+ enable_percpu_irq(imsic_parent_irq, irq_get_trigger_type(imsic_parent_irq));
+
+ /* Initialize the IMSIC registers to enable the interrupt delivery */
+ imsic_hw_states_init();

return 0;
}
@@ -162,6 +169,22 @@ static int imsic_dying_cpu(unsigned int cpu)
return 0;
}

+static int imsic_pm_notifier(struct notifier_block *self, unsigned long cmd, void *v)
+{
+ switch (cmd) {
+ case CPU_PM_EXIT:
+ /* Initialize the IMSIC registers to enable the interrupt delivery */
+ imsic_hw_states_init();
+ break;
+ }
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block imsic_pm_notifier_block = {
+ .notifier_call = imsic_pm_notifier,
+};
+
static int __init imsic_early_probe(struct fwnode_handle *fwnode)
{
struct irq_domain *domain;
@@ -199,7 +222,7 @@ static int __init imsic_early_probe(struct fwnode_handle *fwnode)
cpuhp_setup_state(CPUHP_AP_IRQ_RISCV_IMSIC_STARTING, "irqchip/riscv/imsic:starting",
imsic_starting_cpu, imsic_dying_cpu);

- return 0;
+ return cpu_pm_register_notifier(&imsic_pm_notifier_block);
}

static int __init imsic_early_dt_init(struct device_node *node, struct device_node *parent)
--
2.51.0