From: Linus Walleij <linus.walleij@linaro.org>
Date: Tue, 26 Sep 2023 09:13:44 +0000 (+0200)
Subject: watchdog: ixp4xx: Make sure restart always works
X-Git-Tag: v6.1.63~54
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=8803da01fe1b4ca3d37745283f7e73c6c2558c0c;p=sdk%2Femulator%2Femulator-kernel.git

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@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230926-ixp4xx-wdt-restart-v2-1-15cf4639b423@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/drivers/watchdog/ixp4xx_wdt.c b/drivers/watchdog/ixp4xx_wdt.c
index 281a48d9889f..0fc91e9c4a77 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
@@ -120,14 +139,17 @@ static void ixp4xx_clock_action(void *d)
 
 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);
@@ -153,7 +175,7 @@ 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;