linux-kernel - [PATCH] watchdog: imx7ulp_wdt: Keep WDOG running until A55 enters WFI on i.MX94

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20260203-imx94-wdog-v1-1-7deb76dbe350@nxp.com>
Date: Tue, 03 Feb 2026 16:05:47 +0800
From: "Peng Fan (OSS)" <peng.fan@....nxp.com>
To: Wim Van Sebroeck <wim@...ux-watchdog.org>, 
 Guenter Roeck <linux@...ck-us.net>, Frank Li <Frank.Li@....com>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>
Cc: linux-watchdog@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Ranjani Vaidyanathan <ranjani.vaidyanathan@....com>, 
 Peng Fan <peng.fan@....com>
Subject: [PATCH] watchdog: imx7ulp_wdt: Keep WDOG running until A55 enters
 WFI on i.MX94

From: Ranjani Vaidyanathan <ranjani.vaidyanathan@....com>

On i.MX94, watchdog sources clock from bus clock that will be always on
during the lifecycle of Linux. There is a Low Power Clock Gating(LPCG)
between the bus clock and watchdog, but the LPCG is not exported for
software to control, it is hardware automatically controlled. When
Cortex-A55 executes WFI during suspend flow, the LPCG will automatically
gate off the clock stop watchdog.

So watchdog could always be alive to protect Linux, until WFI is executed.

Introduce a new hardware feature flag to indicate CPU low-power-mode
auto clock gating support, and use it to avoid stopping the watchdog
during suspend when LPCG can safely keep it running.

Add i.MX94-specific watchdog hardware data and DT compatible entry to
enable this behavior.

Signed-off-by: Ranjani Vaidyanathan <ranjani.vaidyanathan@....com>
[peng.fan@....com: rewrite commit log for clarity]
Signed-off-by: Peng Fan <peng.fan@....com>
---
 drivers/watchdog/imx7ulp_wdt.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/imx7ulp_wdt.c b/drivers/watchdog/imx7ulp_wdt.c
index 03479110453ce78a6a89ce8d351ba9ece2f5e2c5..0ae4c0c00138e89854f14edca0fd5fa84591c2d2 100644
--- a/drivers/watchdog/imx7ulp_wdt.c
+++ b/drivers/watchdog/imx7ulp_wdt.c
@@ -56,6 +56,7 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
 struct imx_wdt_hw_feature {
 	bool prescaler_enable;
 	bool post_rcs_wait;
+	bool cpu_lpm_auto_cg;
 	u32 wdog_clock_rate;
 };
 
@@ -360,7 +361,8 @@ static int __maybe_unused imx7ulp_wdt_suspend_noirq(struct device *dev)
 {
 	struct imx7ulp_wdt_device *imx7ulp_wdt = dev_get_drvdata(dev);
 
-	if (watchdog_active(&imx7ulp_wdt->wdd))
+
+	if (watchdog_active(&imx7ulp_wdt->wdd) && !imx7ulp_wdt->hw->cpu_lpm_auto_cg)
 		imx7ulp_wdt_stop(&imx7ulp_wdt->wdd);
 
 	clk_disable_unprepare(imx7ulp_wdt->clk);
@@ -408,10 +410,17 @@ static const struct imx_wdt_hw_feature imx93_wdt_hw = {
 	.wdog_clock_rate = 125,
 };
 
+static const struct imx_wdt_hw_feature imx94_wdt_hw = {
+	.prescaler_enable = true,
+	.wdog_clock_rate = 125,
+	.cpu_lpm_auto_cg = true,
+};
+
 static const struct of_device_id imx7ulp_wdt_dt_ids[] = {
 	{ .compatible = "fsl,imx7ulp-wdt", .data = &imx7ulp_wdt_hw, },
 	{ .compatible = "fsl,imx8ulp-wdt", .data = &imx8ulp_wdt_hw, },
 	{ .compatible = "fsl,imx93-wdt", .data = &imx93_wdt_hw, },
+	{ .compatible = "fsl,imx94-wdt", .data = &imx94_wdt_hw, },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, imx7ulp_wdt_dt_ids);

---
base-commit: 193579fe01389bc21aff0051d13f24e8ea95b47d
change-id: 20260203-imx94-wdog-1e0aa14d661b

Best regards,
-- 
Peng Fan <peng.fan@....com>