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watchdog: imx7ulp_wdt: Keep WDOG running until A55 enters WFI on i.MX94

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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 <ranjani.vaidyanathan@nxp.com>
[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>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20260206-imx94-wdog-v2-1-4dd725faec1f@nxp.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Ranjani Vaidyanathan 2026-02-06 08:23:32 +08:00 committed by Guenter Roeck
parent aed1abf31e
commit 1f5b29add6
1 changed files with 9 additions and 1 deletions
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10
drivers/watchdog/imx7ulp_wdt.c
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@ -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 +361,7 @@ 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 +409,17 @@ 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);