Re: [PATCH v2] watchdog: imx7ulp_wdt: Keep WDOG running until A55 enters WFI on i.MX94
From: Guenter Roeck <linux@roeck-us.net>
Date: 2026-02-06 03:03:57
Also in:
imx, linux-watchdog, lkml
On 2/5/26 16:23, Peng Fan (OSS) wrote:
From: Ranjani Vaidyanathan <redacted> 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 to stop watchdog and resume clock when Cortex-A55 is woke up. So watchdog could always be alive to protect Linux, except Cortex-A platform WFI is executed in Linux suspend flow. 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 <redacted> [peng.fan@nxp.com: rewrite commit log for clarity] Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
quoted hunk ↗ jump to hunk
--- Changes in v2: - Update commit log for clarity - Link to v1: https://lore.kernel.org/r/20260203-imx94-wdog-v1-1-7deb76dbe350@nxp.com (local) --- 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,