On Wed, Feb 04, 2026 at 12:35:01AM +0000, Peng Fan wrote:

quoted

Subject: Re: [PATCH] watchdog: imx7ulp_wdt: Keep WDOG running
until A55 enters WFI on i.MX94

On Tue, Feb 03, 2026 at 04:05:47PM +0800, Peng Fan (OSS) wrote:

quoted

From: Ranjani Vaidyanathan <redacted>

On i.MX94, watchdog sources clock from bus clock that will be

always

quoted

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

quoted

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.

suppose only after suspend's WFI? suppose CPUIDLE's WFI doesn't
affect it?

Only suspend WFI.

Thank you clarify, sugggest rephrase this to avoid confuse. "WFI" is easily
miss leading for CPUIDLE's WFI.

	"until core halt" ?

Frank

Regards
Peng.

quoted

Frank

quoted

Introduce a new hardware feature flag to indicate CPU low-power-

mode

quoted

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

quoted

enable this behavior.

Signed-off-by: Ranjani Vaidyanathan

[off-list ref]

quoted

[peng.fan@nxp.com: rewrite commit log for clarity]
Signed-off-by: Peng Fan <peng.fan@nxp.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..0ae4c0c00138e8985
4f14edca0fd

quoted

5fa84591c2d2 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="

quoted

 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);

quoted

-	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 = {

quoted

 	.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 [off-list ref]