[U-Boot] [PATCH] Fix watchdog timeout setup for mt7623

[Shannon Barber]

Signed-off-by: Shannon Barber <sbarber at dataspeedinc.com>
---
 drivers/watchdog/mtk_wdt.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
index 0b501733f2..a7d4c7a3b8 100644
--- a/drivers/watchdog/mtk_wdt.c
+++ b/drivers/watchdog/mtk_wdt.c
@@ -70,18 +70,30 @@ static int mtk_wdt_expire_now(struct udevice *dev, ulong flags)
 	return 0;
 }
 
-static void mtk_wdt_set_timeout(struct udevice *dev, unsigned int timeout)
+static void mtk_wdt_set_timeout(struct udevice *dev, unsigned int timeout_ms)
 {
 	struct mtk_wdt_priv *priv = dev_get_priv(dev);
 
 	/*
-	 * One bit is the value of 512 ticks
-	 * The clock has 32 KHz
+	 * One WDT_LENGTH count is 512 ticks of the wdt clock
+	 * Clock runs at 32768 Hz
+	 * e.g. 15.625 ms per count (nominal)
+	 * We want the ceiling after dividing timeout_ms by 15.625 ms
+	 * We add 15624 prior to the divide to implement the ceiling
+	 * We prevent over-flow by clamping the timeout_ms value here
+	 *  as the maximum WDT_LENGTH counts is 1023 -> 15.984375 sec
+	 * We also enforce a minimum of 1 count
+	 * Many watchdog peripherals have a self-imposed count of 1
+	 *  that is added to the register counts.
+	 *  The MediaTek docs lack details to know if this is the case here.
+	 *  So we enforce a minimum of 1 to guarantee operation.
 	 */
-	timeout = WDT_LENGTH_TIMEOUT(timeout << 6) | WDT_LENGTH_KEY;
-	writel(timeout, priv->base + MTK_WDT_LENGTH);
-
-	mtk_wdt_reset(dev);
+	if(timeout_ms > 15984) timeout_ms = 15984;
+	u64 timeout_us = timeout_ms * 1000;
+	u32 timeout_cc = (u32) ( (15624 + timeout_us) / 15625 );
+	if(timeout_cc == 0) timeout_cc = 1;
+	u32 length = WDT_LENGTH_TIMEOUT(timeout_cc) | WDT_LENGTH_KEY;
+	writel(length, priv->base + MTK_WDT_LENGTH);
 }
 
 static int mtk_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
@@ -90,6 +102,8 @@ static int mtk_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
 
 	mtk_wdt_set_timeout(dev, timeout);
 
+        mtk_wdt_reset(dev);
+
 	/* Enable watchdog reset signal */
 	setbits_le32(priv->base + MTK_WDT_MODE,
 		     WDT_MODE_EN | WDT_MODE_KEY | WDT_MODE_EXTEN);
-- 
2.17.1