[PATCH 4/5] watchdog: dw_wdt: manage reset line during system suspend/resume

[Artem Shimko]

The watchdog controller reset line is not currently managed during system
suspend/resume. This can lead to an inconsistent hardware state when
resuming from suspend, as the controller may not be properly reinitialized.

Assert the reset line before disabling clocks during suspend to ensure
the controller is held in reset while power is gated. During resume,
deassert the reset after clocks are enabled and before restoring register
state to guarantee the controller is properly initialized. Add proper
error handling for reset control operations during resume with appropriate
cleanup path on failure.

Signed-off-by: Artem Shimko <a.shimko.dev@xxxxxxxxx>
---
 drivers/watchdog/dw_wdt.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
index 27b5098832d5..c2c5dc6e54e7 100644
--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -382,6 +382,8 @@ static int dw_wdt_suspend(struct device *dev)
 	dw_wdt->control = readl(dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
 	dw_wdt->timeout = readl(dw_wdt->regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
 
+	reset_control_assert(dw_wdt->rst);
+
 	clk_disable_unprepare(dw_wdt->pclk);
 	clk_disable_unprepare(dw_wdt->clk);
 
@@ -402,12 +404,22 @@ static int dw_wdt_resume(struct device *dev)
 		return err;
 	}
 
+	err = reset_control_deassert(dw_wdt->rst);
+	if (err)
+		goto unprepare_pclk;
+
 	writel(dw_wdt->timeout, dw_wdt->regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
 	writel(dw_wdt->control, dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
 
 	dw_wdt_ping(&dw_wdt->wdd);
 
 	return 0;
+
+unprepare_clk:
+	clk_disable_unprepare(dw_wdt->pclk);
+	clk_disable_unprepare(dw_wdt->clk);
+
+	return err;
 }
 
 static DEFINE_SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
-- 
2.43.0