linux-kernel - [PATCH RFC 2/3] watchdog: rzg2l

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Date: Wed, 19 Jun 2024 15:09:19 +0300
From: Claudiu <claudiu.beznea@...on.dev>
To: ulf.hansson@...aro.org,
	wim@...ux-watchdog.org,
	linux@...ck-us.net,
	rafael@...nel.org
Cc: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-watchdog@...r.kernel.org,
	claudiu.beznea@...on.dev,
	geert+renesas@...der.be,
	linux-renesas-soc@...r.kernel.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: [PATCH RFC 2/3] watchdog: rzg2l_wdt: Keep the clocks prepared

From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

The watchdog restart handler is called with interrupts disabled. In
rzg2l_wdt_restart() we call clk_prepare_enable() to enable the watchdog
clocks. The prepare part of clk_prepare_enable() may sleep. Sleep in
atomic context should not happen. The clock drivers for all the
micro-architectures where the RZ/G2L watchdog driver is used are not
implementing struct clk_ops::prepare(). Even so, to be sure we are
not hitted by this at some point, keep the watchdog clocks prepared
and only enable them in restart handler. It is guaranteed that
clk_enable() can be called in atomic context.

Reported-by: Ulf Hansson <ulf.hansson@...aro.org>
Closes: https://lore.kernel.org/all/CAPDyKFq1+cL1M9qGY0P58ETHUZHGymxQL0w92emUJPMe7a_GxA@mail.gmail.com
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
---
 drivers/watchdog/rzg2l_wdt.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/rzg2l_wdt.c b/drivers/watchdog/rzg2l_wdt.c
index 2a35f890a288..6e3d7512f38c 100644
--- a/drivers/watchdog/rzg2l_wdt.c
+++ b/drivers/watchdog/rzg2l_wdt.c
@@ -166,8 +166,8 @@ static int rzg2l_wdt_restart(struct watchdog_device *wdev,
 	struct rzg2l_wdt_priv *priv = watchdog_get_drvdata(wdev);
 	int ret;
 
-	clk_prepare_enable(priv->pclk);
-	clk_prepare_enable(priv->osc_clk);
+	clk_enable(priv->pclk);
+	clk_enable(priv->osc_clk);
 
 	if (priv->devtype == WDT_RZG2L) {
 		ret = reset_control_deassert(priv->rstc);
@@ -226,11 +226,28 @@ static const struct watchdog_ops rzg2l_wdt_ops = {
 	.restart = rzg2l_wdt_restart,
 };
 
+static int rzg2l_clks_prepare(struct rzg2l_wdt_priv *priv)
+{
+	int ret;
+
+	ret = clk_prepare(priv->pclk);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare(priv->osc_clk);
+	if (ret)
+		clk_unprepare(priv->pclk);
+
+	return ret;
+}
+
 static void rzg2l_wdt_pm_disable(void *data)
 {
-	struct watchdog_device *wdev = data;
+	struct rzg2l_wdt_priv *priv = data;
 
-	pm_runtime_disable(wdev->parent);
+	pm_runtime_disable(priv->wdev.parent);
+	clk_unprepare(priv->osc_clk);
+	clk_unprepare(priv->pclk);
 }
 
 static int rzg2l_wdt_probe(struct platform_device *pdev)
@@ -275,6 +292,10 @@ static int rzg2l_wdt_probe(struct platform_device *pdev)
 
 	priv->devtype = (uintptr_t)of_device_get_match_data(dev);
 
+	ret = rzg2l_clks_prepare(priv);
+	if (ret)
+		return ret;
+
 	pm_runtime_enable(&pdev->dev);
 
 	priv->wdev.info = &rzg2l_wdt_ident;
@@ -287,7 +308,7 @@ static int rzg2l_wdt_probe(struct platform_device *pdev)
 
 	watchdog_set_drvdata(&priv->wdev, priv);
 	dev_set_drvdata(dev, priv);
-	ret = devm_add_action_or_reset(&pdev->dev, rzg2l_wdt_pm_disable, &priv->wdev);
+	ret = devm_add_action_or_reset(&pdev->dev, rzg2l_wdt_pm_disable, &priv);
 	if (ret)
 		return ret;
 
-- 
2.39.2