linux-kernel - [PATCH 1/2] watchdog: imx2

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Message-Id: <20220109114120.386013-2-alistair@alistair23.me>
Date:   Sun,  9 Jan 2022 21:41:19 +1000
From:   Alistair Francis <alistair@...stair23.me>
To:     linux-kernel@...r.kernel.org, linux@...ck-us.net,
        shawnguo@...nel.org, wim@...ux-watchdog.org,
        linux-watchdog@...r.kernel.org, s.hauer@...gutronix.de,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-imx@....com, kernel@...gutronix.de, festevam@...il.com,
        devicetree@...r.kernel.org, robh+dt@...nel.org,
        Alistair Francis <alistair@...stair23.me>
Subject: [PATCH 1/2] watchdog: imx2_wdg: Alow ping on suspend

The i.MX watchdog cannot be disabled by softwrae once it has been
enabled. This means that it can't be stopped before suspend.

For systems that enter low power mode this is fine, as the watchdog will
be automatically stopped by hardwrae in low power mode. Not all i.MX
platforms support low power mode in the mainline kernel. For example the
i.MX7D does not enter low power mode and so will be rebooted 2 minutes
after entering freeze or mem sleep states.

This patch introduces a device tree property "fsl,ping-during-suspend"
that can be used to enable ping on suspend support for these systems.

Signed-off-by: Alistair Francis <alistair@...stair23.me>
---
 .../bindings/watchdog/fsl-imx-wdt.yaml        |  7 ++++++
 drivers/watchdog/imx2_wdt.c                   | 22 +++++++++++++------
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml
index fb7695515be1..b8660a3c456c 100644
--- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml
+++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml
@@ -55,6 +55,13 @@ properties:
       If present, the watchdog device is configured to assert its
       external reset (WDOG_B) instead of issuing a software reset.
 
+  fsl,ping-during-suspend:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description: |
+      If present, the kernel will ping the watchdog during suspend.
+      This should be used on platforms that don't enter low power mode
+      during suspend.
+
 required:
   - compatible
   - interrupts
diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index 51bfb796898b..9a5fdb3173a8 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -66,6 +66,7 @@ struct imx2_wdt_device {
 	struct watchdog_device wdog;
 	bool ext_reset;
 	bool clk_is_on;
+	bool no_ping;
 };
 
 static bool nowayout = WATCHDOG_NOWAYOUT;
@@ -312,12 +313,14 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
 
 	wdev->ext_reset = of_property_read_bool(dev->of_node,
 						"fsl,ext-reset-output");
+	wdev->no_ping = !of_property_read_bool(dev->of_node, "fsl,ping-during-suspend");
 	platform_set_drvdata(pdev, wdog);
 	watchdog_set_drvdata(wdog, wdev);
 	watchdog_set_nowayout(wdog, nowayout);
 	watchdog_set_restart_priority(wdog, 128);
 	watchdog_init_timeout(wdog, timeout, dev);
-	watchdog_stop_ping_on_suspend(wdog);
+	if (wdev->no_ping)
+		watchdog_stop_ping_on_suspend(wdog);
 
 	if (imx2_wdt_is_running(wdev)) {
 		imx2_wdt_set_timeout(wdog, wdog->timeout);
@@ -366,9 +369,11 @@ static int __maybe_unused imx2_wdt_suspend(struct device *dev)
 		imx2_wdt_ping(wdog);
 	}
 
-	clk_disable_unprepare(wdev->clk);
+	if (wdev->no_ping) {
+		clk_disable_unprepare(wdev->clk);
 
-	wdev->clk_is_on = false;
+		wdev->clk_is_on = false;
+	}
 
 	return 0;
 }
@@ -380,11 +385,14 @@ static int __maybe_unused imx2_wdt_resume(struct device *dev)
 	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
 	int ret;
 
-	ret = clk_prepare_enable(wdev->clk);
-	if (ret)
-		return ret;
+	if (wdev->no_ping) {
+		ret = clk_prepare_enable(wdev->clk);
 
-	wdev->clk_is_on = true;
+		if (ret)
+			return ret;
+
+		wdev->clk_is_on = true;
+	}
 
 	if (watchdog_active(wdog) && !imx2_wdt_is_running(wdev)) {
 		/*
-- 
2.31.1