linux-kernel - [PATCH v2] watchdog: da9052

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Message-Id: <20250129-da9052-v2-1-1ae2b263d936@gmail.com>
Date: Wed, 29 Jan 2025 10:27:52 +0100
From: Marcus Folkesson <marcus.folkesson@...il.com>
To: Support Opensource <support.opensource@...semi.com>, 
 Wim Van Sebroeck <wim@...ux-watchdog.org>, 
 Guenter Roeck <linux@...ck-us.net>
Cc: linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Marcus Folkesson <marcus.folkesson@...il.com>
Subject: [PATCH v2] watchdog: da9052_wdt: respect TWDMIN

We have to wait at least the minimium time for the watchdog window
(TWDMIN) before writings to the wdt register after the
watchdog is activated.
Otherwise the chip will assert TWD_ERROR and power down to reset mode.

Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
---
The current implementation does not respect the time window for all
cases not it handle when the jiffie wrap around.
E.g. setting a new timeout and immediately perform a 'ping' causes the
chip to assert TWD_ERROR.
---
Changes in v2:
- Use the right author email.
- Link to v1: https://lore.kernel.org/r/20250129-da9052-v1-1-aa0dfc2ad595@gmail.com
---
 drivers/watchdog/da9052_wdt.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/drivers/watchdog/da9052_wdt.c b/drivers/watchdog/da9052_wdt.c
index 77039f2f0be54273df1666fe40c413b6c89285a1..5ca957a6c2219d99cb3e653205e3f556f7cfb56f 100644
--- a/drivers/watchdog/da9052_wdt.c
+++ b/drivers/watchdog/da9052_wdt.c
@@ -45,6 +45,21 @@ static const struct {
 	{ 7, 131 },
 };
 
+static void da9052_wdt_wait_for_twdmin(struct watchdog_device *wdt_dev)
+{
+	struct da9052_wdt_data *driver_data = watchdog_get_drvdata(wdt_dev);
+	unsigned long msecs, twdmin, jnow = jiffies;
+
+	/*
+	 * The host must wait at least TWDMIN ms between writings to the watchdog
+	 * register or the DA9052 will assert TWD_ERROR and power down to RESET mode.
+	 */
+	twdmin  = driver_data->jpast + msecs_to_jiffies(DA9052_TWDMIN);
+	if (time_before(jnow, twdmin)) {
+		msecs = jiffies_to_msecs(twdmin - jnow);
+		mdelay(msecs);
+	}
+}
 
 static int da9052_wdt_set_timeout(struct watchdog_device *wdt_dev,
 				  unsigned int timeout)
@@ -53,6 +68,7 @@ static int da9052_wdt_set_timeout(struct watchdog_device *wdt_dev,
 	struct da9052 *da9052 = driver_data->da9052;
 	int ret, i;
 
+	da9052_wdt_wait_for_twdmin(wdt_dev);
 	/*
 	 * Disable the Watchdog timer before setting
 	 * new time out.
@@ -89,8 +105,8 @@ static int da9052_wdt_set_timeout(struct watchdog_device *wdt_dev,
 		}
 
 		wdt_dev->timeout = timeout;
-		driver_data->jpast = jiffies;
 	}
+	driver_data->jpast = jiffies;
 
 	return 0;
 }
@@ -109,16 +125,9 @@ static int da9052_wdt_ping(struct watchdog_device *wdt_dev)
 {
 	struct da9052_wdt_data *driver_data = watchdog_get_drvdata(wdt_dev);
 	struct da9052 *da9052 = driver_data->da9052;
-	unsigned long msec, jnow = jiffies;
 	int ret;
 
-	/*
-	 * We have a minimum time for watchdog window called TWDMIN. A write
-	 * to the watchdog before this elapsed time should cause an error.
-	 */
-	msec = (jnow - driver_data->jpast) * 1000/HZ;
-	if (msec < DA9052_TWDMIN)
-		mdelay(msec);
+	da9052_wdt_wait_for_twdmin(wdt_dev);
 
 	/* Reset the watchdog timer */
 	ret = da9052_reg_update(da9052, DA9052_CONTROL_D_REG,
@@ -130,8 +139,11 @@ static int da9052_wdt_ping(struct watchdog_device *wdt_dev)
 	 * FIXME: Reset the watchdog core, in general PMIC
 	 * is supposed to do this
 	 */
-	return da9052_reg_update(da9052, DA9052_CONTROL_D_REG,
+	ret = da9052_reg_update(da9052, DA9052_CONTROL_D_REG,
 				 DA9052_CONTROLD_WATCHDOG, 0 << 7);
+
+	driver_data->jpast = jiffies;
+	return ret;
 }
 
 static const struct watchdog_info da9052_wdt_info = {
@@ -187,6 +199,7 @@ static int da9052_wdt_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	driver_data->jpast = jiffies;
 	return devm_watchdog_register_device(dev, &driver_data->wdt);
 }
 

---
base-commit: 05dbaf8dd8bf537d4b4eb3115ab42a5fb40ff1f5
change-id: 20250129-da9052-661dfbb7de38

Best regards,
-- 
Marcus Folkesson <marcus.folkesson@...il.com>