irqchip/loongson-htvec: Add suspend/resume support

Add suspend/resume support for HTVEC irqchip, which is needed for
upcoming suspend/hibernation.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221020073527.541845-2-chenhuacai@loongson.cn

drivers/irqchip/irq-loongson-htvec.c

@@ -16,6 +16,7 @@
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/syscore_ops.h>
 
 /* Registers */
 #define HTVEC_EN_OFF		0x20
@@ -29,6 +30,7 @@ struct htvec {
 	void __iomem		*base;
 	struct irq_domain	*htvec_domain;
 	raw_spinlock_t		htvec_lock;
+	u32			saved_vec_en[HTVEC_MAX_PARENT_IRQ];
 };
 
 static struct htvec *htvec_priv;
@@ -156,6 +158,29 @@ static void htvec_reset(struct htvec *priv)
 	}
 }
 
+static int htvec_suspend(void)
+{
+	int i;
+
+	for (i = 0; i < htvec_priv->num_parents; i++)
+		htvec_priv->saved_vec_en[i] = readl(htvec_priv->base + HTVEC_EN_OFF + 4 * i);
+
+	return 0;
+}
+
+static void htvec_resume(void)
+{
+	int i;
+
+	for (i = 0; i < htvec_priv->num_parents; i++)
+		writel(htvec_priv->saved_vec_en[i], htvec_priv->base + HTVEC_EN_OFF + 4 * i);
+}
+
+static struct syscore_ops htvec_syscore_ops = {
+	.suspend = htvec_suspend,
+	.resume = htvec_resume,
+};
+
 static int htvec_init(phys_addr_t addr, unsigned long size,
 		int num_parents, int parent_irq[], struct fwnode_handle *domain_handle)
 {
@@ -188,6 +213,8 @@ static int htvec_init(phys_addr_t addr, unsigned long size,
 
 	htvec_priv = priv;
 
+	register_syscore_ops(&htvec_syscore_ops);
+
 	return 0;
 
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