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25.09.2010 21:38, Aleksandar Radovanovic wrote:
> Re the patch, I agree - applying that patch will effectively turn the
> driver into a softdog.

To be honest: bcrm47xx_wdt driver isn't a hardware watchdog either. I had spent
some time inspecting the module source and googling around and it seems that the
fire time for the ssb hardware watchdog being set in "tick" (cycles qty) units
maxing at 0xFFFFFFF. This means that fire time would be ~2.5 seconds on 100MHz
systems, and ~2 seconds on 133MHz systems. I don't know the implementation
details for broadcom boards so I can't tell for sure if any plls are used to
make CPU run at 240Mhz. If the watchdog timer will be clocked at CPU freq then
it would lower fire time to ~1 second.

Looks like that such a low fire time is inappropriate for the non-realtime
kernel and the developer of the driver "extended" hardware watchdog timer with a
software one. Thus the current driver acts like this: wait till software timer
fires -> warn user that the watchdog will fire soon -> arm hardware watchdog to
fire after 0xFFFFFFF cycles -> do nothing waiting till hardware timer fires and
reboots the device.

It is obvious that in case some huge kernel disaster happen this watchdog
wouldn't be able to reboot the device making driver almost the same as softdog.
For now I had modified my working copy of openwrt sources to exclude
bcrm47xx_wdt driver from build (it makes possible to use softdog instead).

Still it would be great to figure out why does the bcrm47xx_wdt driver work with
your Asus WL-500gP v1 and don't work with my D-Link DIR-320.

- -- 
Best regards,
Alexey Loukianov                          mailto:[email protected]
System Engineer,                            Mob.:+7(926)218-1320
*nix Specialist

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