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From: "Alice Guo (OSS)" <alice.guo@oss.nxp.com>
To: m.felsch@pengutronix.de, linux@roeck-us.net,
	wim@linux-watchdog.org, shawnguo@kernel.org,
	s.hauer@pengutronix.de, festevam@gmail.com
Cc: kernel@pengutronix.de, linux-imx@nxp.com,
	linux-watchdog@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/7] watchdog: imx7ulp: Add explict memory barrier for unlock sequence
Date: Thu, 25 Aug 2022 16:32:51 +0800	[thread overview]
Message-ID: <20220825083256.14565-3-alice.guo@oss.nxp.com> (raw)
In-Reply-To: <20220825083256.14565-1-alice.guo@oss.nxp.com>

From: Jacky Bai <ping.bai@nxp.com>

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 <ye.li@nxp.com>
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Signed-off-by: Alice Guo <alice.guo@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
---

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;
 
 	local_irq_disable();
+
+	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;
-- 
2.17.1


  parent reply	other threads:[~2022-08-25  8:33 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-25  8:32 [PATCH v2 0/7] watchdog: imx7ulp_wdt: update i.MX7ULP WDOG timer driver Alice Guo (OSS)
2022-08-25  8:32 ` [PATCH v2 1/7] watchdog: imx7ulp: Move suspend/resume to noirq phase Alice Guo (OSS)
2022-09-25 17:37   ` Guenter Roeck
2022-08-25  8:32 ` Alice Guo (OSS) [this message]
2022-09-25 17:37   ` [PATCH v2 2/7] watchdog: imx7ulp: Add explict memory barrier for unlock sequence Guenter Roeck
2022-08-25  8:32 ` [PATCH v2 3/7] watchdog: imx7ulp_wdt: Check CMD32EN in wdog init Alice Guo (OSS)
2022-09-25 17:37   ` Guenter Roeck
2022-08-25  8:32 ` [PATCH v2 4/7] watchdog: imx7ulp_wdt: Fix RCS timeout issue Alice Guo (OSS)
2022-09-25 17:38   ` Guenter Roeck
2022-08-25  8:32 ` [PATCH v2 5/7] watchdog: imx7ulp_wdt: Handle wdog reconfigure failure Alice Guo (OSS)
2022-09-25 17:38   ` Guenter Roeck
2022-08-25  8:32 ` [PATCH v2 6/7] watchdog: imx7ulp_wdt: init wdog when it was active Alice Guo (OSS)
2022-09-25 17:38   ` Guenter Roeck
2022-08-25  8:32 ` [PATCH v2 7/7] watchdog: imx93: add watchdog timer on imx93 Alice Guo (OSS)
2022-09-25 17:38   ` Guenter Roeck
2022-09-06  2:11 ` [PATCH v2 0/7] watchdog: imx7ulp_wdt: update i.MX7ULP WDOG timer driver Alice Guo (OSS)

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