From c65f203f7ede7d78f5540c88a265437936404be2 Mon Sep 17 00:00:00 2001
From: Nick Hu <nick.hu@sifive.com>
Date: Tue, 15 Aug 2023 17:02:16 +0800
Subject: [PATCH] serial: sifive: Add suspend and resume operations

References: bsc#1214683 (PREEMPT_RT prerequisite backports)
Patch-mainline: v6.6-rc1
Git-commit: 8a6498f2b94333f1793bc912b11830655f975470

If the Sifive Uart is not used as the wake up source, suspend the uart
before the system enter the suspend state to prevent it woken up by
unexpected uart interrupt. Resume the uart once the system woken up.

Signed-off-by: Nick Hu <nick.hu@sifive.com>
Reviewed-by: Ben Dooks <ben.dooks@codethink.co.uk>
Link: https://lore.kernel.org/r/20230815090216.2575971-1-nick.hu@sifive.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 drivers/tty/serial/sifive.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
index e2efc3f84eff..d195c5de52e7 100644
--- a/drivers/tty/serial/sifive.c
+++ b/drivers/tty/serial/sifive.c
@@ -1019,6 +1019,23 @@ static int sifive_serial_remove(struct platform_device *dev)
 	return 0;
 }
 
+static int sifive_serial_suspend(struct device *dev)
+{
+	struct sifive_serial_port *ssp = dev_get_drvdata(dev);
+
+	return uart_suspend_port(&sifive_serial_uart_driver, &ssp->port);
+}
+
+static int sifive_serial_resume(struct device *dev)
+{
+	struct sifive_serial_port *ssp = dev_get_drvdata(dev);
+
+	return uart_resume_port(&sifive_serial_uart_driver, &ssp->port);
+}
+
+DEFINE_SIMPLE_DEV_PM_OPS(sifive_uart_pm_ops, sifive_serial_suspend,
+			 sifive_serial_resume);
+
 static const struct of_device_id sifive_serial_of_match[] = {
 	{ .compatible = "sifive,fu540-c000-uart0" },
 	{ .compatible = "sifive,uart0" },
@@ -1031,6 +1048,7 @@ static struct platform_driver sifive_serial_platform_driver = {
 	.remove		= sifive_serial_remove,
 	.driver		= {
 		.name	= SIFIVE_SERIAL_NAME,
+		.pm = pm_sleep_ptr(&sifive_uart_pm_ops),
 		.of_match_table = sifive_serial_of_match,
 	},
 };