Patch "watchdog: ixp4xx: Make sure restart always works" has been added to the 6.5-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    watchdog: ixp4xx: Make sure restart always works

to the 6.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     watchdog-ixp4xx-make-sure-restart-always-works.patch
and it can be found in the queue-6.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 76225768916cd10339bb30c0725c827f704e618f
Author: Linus Walleij <linus.walleij@xxxxxxxxxx>
Date:   Tue Sep 26 11:13:44 2023 +0200

    watchdog: ixp4xx: Make sure restart always works
    
    [ Upstream commit b4075ecfe348a44209534c75ad72392c63a489a6 ]
    
    The IXP4xx watchdog in early "A0" silicon is unreliable and
    cannot be registered, however for some systems such as the
    USRobotics USR8200 the watchdog is the only restart option,
    so implement a "dummy" watchdog that can only support restart
    in this case.
    
    Fixes: 1aea522809e6 ("watchdog: ixp4xx: Implement restart")
    Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
    Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230926-ixp4xx-wdt-restart-v2-1-15cf4639b423@xxxxxxxxxx
    Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
    Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/watchdog/ixp4xx_wdt.c b/drivers/watchdog/ixp4xx_wdt.c
index 607ce4b8df574..ec0c08652ec2f 100644
--- a/drivers/watchdog/ixp4xx_wdt.c
+++ b/drivers/watchdog/ixp4xx_wdt.c
@@ -105,6 +105,25 @@ static const struct watchdog_ops ixp4xx_wdt_ops = {
 	.owner = THIS_MODULE,
 };
 
+/*
+ * The A0 version of the IXP422 had a bug in the watchdog making
+ * is useless, but we still need to use it to restart the system
+ * as it is the only way, so in this special case we register a
+ * "dummy" watchdog that doesn't really work, but will support
+ * the restart operation.
+ */
+static int ixp4xx_wdt_dummy(struct watchdog_device *wdd)
+{
+	return 0;
+}
+
+static const struct watchdog_ops ixp4xx_wdt_restart_only_ops = {
+	.start = ixp4xx_wdt_dummy,
+	.stop = ixp4xx_wdt_dummy,
+	.restart = ixp4xx_wdt_restart,
+	.owner = THIS_MODULE,
+};
+
 static const struct watchdog_info ixp4xx_wdt_info = {
 	.options = WDIOF_KEEPALIVEPING
 		| WDIOF_MAGICCLOSE
@@ -114,14 +133,17 @@ static const struct watchdog_info ixp4xx_wdt_info = {
 
 static int ixp4xx_wdt_probe(struct platform_device *pdev)
 {
+	static const struct watchdog_ops *iwdt_ops;
 	struct device *dev = &pdev->dev;
 	struct ixp4xx_wdt *iwdt;
 	struct clk *clk;
 	int ret;
 
 	if (!(read_cpuid_id() & 0xf) && !cpu_is_ixp46x()) {
-		dev_err(dev, "Rev. A0 IXP42x CPU detected - watchdog disabled\n");
-		return -ENODEV;
+		dev_info(dev, "Rev. A0 IXP42x CPU detected - only restart supported\n");
+		iwdt_ops = &ixp4xx_wdt_restart_only_ops;
+	} else {
+		iwdt_ops = &ixp4xx_wdt_ops;
 	}
 
 	iwdt = devm_kzalloc(dev, sizeof(*iwdt), GFP_KERNEL);
@@ -141,7 +163,7 @@ static int ixp4xx_wdt_probe(struct platform_device *pdev)
 		iwdt->rate = IXP4XX_TIMER_FREQ;
 
 	iwdt->wdd.info = &ixp4xx_wdt_info;
-	iwdt->wdd.ops = &ixp4xx_wdt_ops;
+	iwdt->wdd.ops = iwdt_ops;
 	iwdt->wdd.min_timeout = 1;
 	iwdt->wdd.max_timeout = U32_MAX / iwdt->rate;
 	iwdt->wdd.parent = dev;