irqchip/loongson-pch-lpc: Add suspend/resume support

Add suspend/resume support for PCH-LPC 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/20221020073527.541845-5-chenhuacai@loongson.cn

drivers/irqchip/irq-loongson-pch-lpc.c

@@ -13,6 +13,7 @@
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqdomain.h>
 #include <linux/kernel.h>
+#include <linux/syscore_ops.h>
 
 /* Registers */
 #define LPC_INT_CTL		0x00
@@ -34,6 +35,7 @@ struct pch_lpc {
 	u32			saved_reg_pol;
 };
 
+static struct pch_lpc *pch_lpc_priv;
 struct fwnode_handle *pch_lpc_handle;
 
 static void lpc_irq_ack(struct irq_data *d)
@@ -147,6 +149,26 @@ static int pch_lpc_disabled(struct pch_lpc *priv)
 			(readl(priv->base + LPC_INT_STS) == 0xffffffff);
 }
 
+static int pch_lpc_suspend(void)
+{
+	pch_lpc_priv->saved_reg_ctl = readl(pch_lpc_priv->base + LPC_INT_CTL);
+	pch_lpc_priv->saved_reg_ena = readl(pch_lpc_priv->base + LPC_INT_ENA);
+	pch_lpc_priv->saved_reg_pol = readl(pch_lpc_priv->base + LPC_INT_POL);
+	return 0;
+}
+
+static void pch_lpc_resume(void)
+{
+	writel(pch_lpc_priv->saved_reg_ctl, pch_lpc_priv->base + LPC_INT_CTL);
+	writel(pch_lpc_priv->saved_reg_ena, pch_lpc_priv->base + LPC_INT_ENA);
+	writel(pch_lpc_priv->saved_reg_pol, pch_lpc_priv->base + LPC_INT_POL);
+}
+
+static struct syscore_ops pch_lpc_syscore_ops = {
+	.suspend = pch_lpc_suspend,
+	.resume = pch_lpc_resume,
+};
+
 int __init pch_lpc_acpi_init(struct irq_domain *parent,
 					struct acpi_madt_lpc_pic *acpi_pchlpc)
 {
@@ -191,7 +213,10 @@ int __init pch_lpc_acpi_init(struct irq_domain *parent,
 	parent_irq = irq_create_fwspec_mapping(&fwspec);
 	irq_set_chained_handler_and_data(parent_irq, lpc_irq_dispatch, priv);
 
+	pch_lpc_priv = priv;
 	pch_lpc_handle = irq_handle;
+	register_syscore_ops(&pch_lpc_syscore_ops);
+
 	return 0;
 
 free_irq_handle: