linux-kernel - [PATCH 2/2] watchdog: dw_wdt: Try to get a 30 second watchdog by default

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Date:	Wed, 21 Jan 2015 15:17:23 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Wim Van Sebroeck <wim@...ana.be>
Cc:	Heiko Stuebner <heiko@...ech.de>,
	Lunxue Dai <lunxue.dai@...k-chips.com>,
	Jisheng Zhang <jszhang@...vell.com>,
	Dinh Nguyen <dinguyen@...era.com>,
	Doug Anderson <dianders@...omium.org>,
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] watchdog: dw_wdt: Try to get a 30 second watchdog by default

The dw_wdt_set_top() function takes in a value in seconds.  In
dw_wdt_open() we were calling it with a value that's supposed to
represent the maximum value programmed into the "top" register with a
comment saying that we were trying to set the watchdog to its maximum
value.  Instead we ended up setting the watchdog to ~15 seconds.

Let's fix this.  However, setting things to the "max" gives me an 86
second watchdog in the system I'm looking at.  86 seconds feels a
little too long.  We'll explicitly choose 30 seconds as a more
reasonable value.

NOTE: Ideally this driver should be transitioned to be a real watchdog
driver.  Then we could use "watchdog_init_timeout" and let the timeout
be specified in a number of ways (device tree, module parameter, etc).
This patch should be considered a bit of a stopgap solution.

Signed-off-by: Doug Anderson <dianders@...omium.org>
---
 drivers/watchdog/dw_wdt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
index fc92bea..cc2805d 100644
--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -51,6 +51,8 @@
 /* The maximum TOP (timeout period) value that can be set in the watchdog. */
 #define DW_WDT_MAX_TOP		15

+#define DW_WDT_DEFAULT_SECONDS	30
+
 static bool nowayout = WATCHDOG_NOWAYOUT;
 module_param(nowayout, bool, 0);
 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
@@ -167,9 +169,9 @@ static int dw_wdt_open(struct inode *inode, struct file *filp)
 	if (!dw_wdt_is_enabled()) {
 		/*
 		 * The watchdog is not currently enabled. Set the timeout to
-		 * the maximum and then start it.
+		 * something reasonable and then start it.
 		 */
-		dw_wdt_set_top(DW_WDT_MAX_TOP);
+		dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS);
 		dw_wdt_keepalive();
 		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
 		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
-- 
2.2.0.rc0.207.ga3a616c

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