[PATCH v3 1/3] watchdog: rzv2h_wdt: Propagate WDTDCR access errors

From: Lad Prabhakar <[email protected]>

The WDTDCR helpers currently access the register directly using
`readl()`/`writel()` and therefore cannot report failures to their callers.
WDTDCR is located in a shared syscon region and will be accessed through
regmap in a subsequent change, where register accesses can fail.

Make `rzt2h_wdt_wdtdcr_count_start()` and `rzt2h_wdt_wdtdcr_count_stop()`
return an error so their callers can propagate failures.

Handle these errors in the watchdog start, stop and restart paths and
unwind resources acquired before the WDTDCR access. In particular, restore
the reset and clock state and release the runtime PM reference as
appropriate when an access fails.

The helpers still return zero with the current `readl()`/`writel()`
implementation, so this change does not alter the driver's behaviour by
itself. It prepares the error handling required for the subsequent regmap
conversion of WDTDCR access.

Signed-off-by: Lad Prabhakar <[email protected]>
---
v2->v3:
- New patch, split from v2 patch #1 to make thing easier to review.
---
 drivers/watchdog/rzv2h_wdt.c | 49 ++++++++++++++++++++++++++++--------
 1 file changed, 38 insertions(+), 11 deletions(-)

diff --git a/drivers/watchdog/rzv2h_wdt.c b/drivers/watchdog/rzv2h_wdt.c
index 3b6abb66a1da..b770226f785e 100644
--- a/drivers/watchdog/rzv2h_wdt.c
+++ b/drivers/watchdog/rzv2h_wdt.c
@@ -89,18 +89,22 @@ static int rzv2h_wdt_ping(struct watchdog_device *wdev)
 	return 0;
 }
 
-static void rzt2h_wdt_wdtdcr_count_stop(struct rzv2h_wdt_priv *priv)
+static int rzt2h_wdt_wdtdcr_count_stop(struct rzv2h_wdt_priv *priv)
 {
 	u32 reg = readl(priv->wdtdcr + WDTDCR);
 
 	writel(reg | WDTDCR_WDTSTOPCTRL, priv->wdtdcr + WDTDCR);
+
+	return 0;
 }
 
-static void rzt2h_wdt_wdtdcr_count_start(struct rzv2h_wdt_priv *priv)
+static int rzt2h_wdt_wdtdcr_count_start(struct rzv2h_wdt_priv *priv)
 {
 	u32 reg = readl(priv->wdtdcr + WDTDCR);
 
 	writel(reg & ~WDTDCR_WDTSTOPCTRL, priv->wdtdcr + WDTDCR);
+
+	return 0;
 }
 
 static void rzv2h_wdt_setup(struct watchdog_device *wdev, u16 wdtcr)
@@ -150,8 +154,14 @@ static int rzv2h_wdt_start(struct watchdog_device *wdev)
 	rzv2h_wdt_setup(wdev, of_data->cks_max | WDTCR_RPSS_100 |
 			WDTCR_RPES_0 | of_data->tops);
 
-	if (priv->of_data->wdtdcr)
-		rzt2h_wdt_wdtdcr_count_start(priv);
+	if (priv->of_data->wdtdcr) {
+		ret = rzt2h_wdt_wdtdcr_count_start(priv);
+		if (ret) {
+			reset_control_assert(priv->rstc);
+			pm_runtime_put(wdev->parent);
+			return ret;
+		}
+	}
 
 	/*
 	 * Down counting starts after writing the sequence 00h -> FFh to the
@@ -171,8 +181,13 @@ static int rzv2h_wdt_stop(struct watchdog_device *wdev)
 	if (ret)
 		return ret;
 
-	if (priv->of_data->wdtdcr)
-		rzt2h_wdt_wdtdcr_count_stop(priv);
+	if (priv->of_data->wdtdcr) {
+		ret = rzt2h_wdt_wdtdcr_count_stop(priv);
+		if (ret) {
+			reset_control_deassert(priv->rstc);
+			return ret;
+		}
+	}
 
 	pm_runtime_put(wdev->parent);
 
@@ -188,9 +203,10 @@ static int rzv2h_wdt_restart(struct watchdog_device *wdev,
 			     unsigned long action, void *data)
 {
 	struct rzv2h_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	bool active = watchdog_active(wdev);
 	int ret;
 
-	if (!watchdog_active(wdev)) {
+	if (!active) {
 		ret = clk_enable(priv->pclk);
 		if (ret)
 			return ret;
@@ -234,8 +250,19 @@ static int rzv2h_wdt_restart(struct watchdog_device *wdev,
 	rzv2h_wdt_setup(wdev, priv->of_data->cks_min | WDTCR_RPSS_25 |
 			WDTCR_RPES_75 | WDTCR_TOPS_1024);
 
-	if (priv->of_data->wdtdcr)
-		rzt2h_wdt_wdtdcr_count_start(priv);
+	if (priv->of_data->wdtdcr) {
+		ret = rzt2h_wdt_wdtdcr_count_start(priv);
+		if (ret) {
+			if (!active) {
+				reset_control_assert(priv->rstc);
+				clk_disable(priv->oscclk);
+				clk_disable(priv->pclk);
+			} else {
+				reset_control_reset(priv->rstc);
+			}
+			return ret;
+		}
+	}
 
 	rzv2h_wdt_ping(wdev);
 
@@ -266,11 +293,11 @@ static int rzt2h_wdt_wdtdcr_init(struct platform_device *pdev,
 	if (ret)
 		return ret;
 
-	rzt2h_wdt_wdtdcr_count_stop(priv);
+	ret = rzt2h_wdt_wdtdcr_count_stop(priv);
 
 	pm_runtime_put(&pdev->dev);
 
-	return 0;
+	return ret;
 }
 
 static int rzv2h_wdt_probe(struct platform_device *pdev)
-- 
2.43.0