Re: [PATCH 1/2] watchdog: dw_wdt: pat the watchdog before enabling it

From: Guenter Roeck
Date: Wed Jan 21 2015 - 18:35:56 EST


On 01/21/2015 03:17 PM, Doug Anderson wrote:
On some dw_wdt implementations the "top" register may be initted to 0
at bootup. In such a case, each "pat" of the watchdog will reset the
timer to 0xffff. That's pretty short.

The input clock of the wdt can be any of a wide range of values. On
an rk3288 system, I've seen the wdt clock be 24.75 MHz. That means
each tick is ~40ns and we'll count to 0xffff in ~2.6ms.

Because of the above two facts, it's a really good idea to pat the
watchdog after initting the "top" register properly and before
enabling the watchdog. If you don't then there's no way we'll get the
next heartbeat in time.

Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
---

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

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