linux-kernel - [PATCH 1/2] irqchip/riscv-imsic: Restore the IMSIC registers

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Message-Id: <20250709025516.28051-2-nick.hu@sifive.com>
Date: Wed,  9 Jul 2025 10:55:15 +0800
From: Nick Hu <nick.hu@...ive.com>
To: Alexandre Ghiti <alex@...ti.fr>,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Nick Hu <nick.hu@...ive.com>,
	Anup Patel <anup@...infault.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>
Subject: [PATCH 1/2] irqchip/riscv-imsic: Restore the IMSIC registers

When the system woken up from the low power state, the IMSIC might be in
the reset state. Therefore adding the CPU PM callbacks to restore the
IMSIC register when the cpu resume from the low power state.

Signed-off-by: Nick Hu <nick.hu@...ive.com>
Reviewed-by: Yong-Xuan Wang <yongxuan.wang@...ive.com>
Reviewed-by: Cyan Yang <cyan.yang@...ive.com>
---
 drivers/irqchip/irq-riscv-imsic-early.c | 41 ++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/drivers/irqchip/irq-riscv-imsic-early.c b/drivers/irqchip/irq-riscv-imsic-early.c
index d9ae87808651..f64d9a0642bb 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/interrupt.h>
 #include <linux/io.h>
 #include <linux/irq.h>
@@ -109,14 +110,8 @@ 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_restore(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();
 
@@ -128,6 +123,19 @@ 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));
+
+	/* Restore the imsic reg */
+	imsic_restore();
 
 	return 0;
 }
@@ -143,6 +151,23 @@ static int imsic_dying_cpu(unsigned int cpu)
 	return 0;
 }
 
+static int imsic_notifier(struct notifier_block *self, unsigned long cmd,
+			  void *v)
+{
+	switch (cmd) {
+	case CPU_PM_EXIT:
+		/* Restore the imsic reg */
+		imsic_restore();
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block imsic_notifier_block = {
+	.notifier_call = imsic_notifier,
+};
+
 static int __init imsic_early_probe(struct fwnode_handle *fwnode)
 {
 	struct irq_domain *domain;
@@ -180,7 +205,7 @@ 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_notifier_block);
 }
 
 static int __init imsic_early_dt_init(struct device_node *node, struct device_node *parent)
-- 
2.17.1