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Subject[PATCH v2 2/7] watchdog: imx7ulp: Add explict memory barrier for unlock sequence
From: Jacky Bai <>

When reconfiguring the WDOG Timer of i.MX7ULP, there is a certain
probability causes it to reset. The reason is that the CMD32EN of the
WDOG Timer of i.MX7ULP is disabled in bootloader. The unlock sequence
are two 16-bit writes to the CNT register within 16 bus clocks. Adding
mb() is to guarantee that two 16-bit writes are finished within 16 bus
clocks. Memory barriers cannot be added between these two 16-bit writes
so that writel_relaxed is used.

Suggested-by: Ye Li <>
Signed-off-by: Jacky Bai <>
Signed-off-by: Alice Guo <>
Reviewed-by: Ye Li <>

Changes for v2:
- add the reason why memory barriers are added for unlock sequence in commit log

drivers/watchdog/imx7ulp_wdt.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/watchdog/imx7ulp_wdt.c b/drivers/watchdog/imx7ulp_wdt.c
index 014f497ea0dc..b8ac0cb04d2f 100644
--- a/drivers/watchdog/imx7ulp_wdt.c
+++ b/drivers/watchdog/imx7ulp_wdt.c
@@ -179,9 +179,13 @@ static int imx7ulp_wdt_init(void __iomem *base, unsigned int timeout)
int ret;

+ mb();
/* unlock the wdog for reconfiguration */
writel_relaxed(UNLOCK_SEQ0, base + WDOG_CNT);
writel_relaxed(UNLOCK_SEQ1, base + WDOG_CNT);
+ mb();
ret = imx7ulp_wdt_wait(base, WDOG_CS_ULK);
if (ret)
goto init_out;
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