[Avila] watchdog on avila (GW-2348)

[Chris Lang]

To All,

I will just piggy back on what Tim said...

The internal IXP watchdog is not adequate on these boards to use as a
watchdog as it doesn't reset flash, as stated, if it is used, you will
experience boot problems if the watchdog resets during a flash read or
write. 

The reason the IXP42x watchdog is not used is that there was a bug in the
silicon of the IXP42x when this was designed that made the watchdog hang the
CPU upon a reset, hence the reason why other IXP hardware is configured the
same.

The external watchdog can be used, but as Tim said can be difficult to
strobe from as you have to strobe it once a second. We, Gateworks, configure
GPIO14 from within redboot as a 4.7mhz clock which strobes the watchdog
adequately but only protects against processor lock-ups, not from software
lock-ups, typically not what you want. It has been noted that attempting to
strobe the watchdog with a heartbeat has a high percentage chance of
failing, and has seen to fail when the board comes under heavy load.

The resistors are not loaded by default on the GW2348 series because there
is not an ability to enable/disable the watchdog. If the resistor is loaded,
you have to strobe the watchdog, or the board is unusable. The loading of
the resistors is an ordering option for 100pc min purchases.

There is also issues with programming the boards through jtag with the
watchdog resistor loaded, this has been resolved with the DOS version of our
utility, but no other jtag programmers/debuggers currently work with the
resistor loaded.

Thanks,
Chris Lang
clang at gateworks.com


-----Original Message-----
From: avila-bounces at lists.gateworks.com
[mailto:avila-bounces at lists.gateworks.com] On Behalf Of David Acker
Sent: Thursday, April 10, 2008 9:08 AM
To: Tim Harvey
Cc: avila at lists.gateworks.com
Subject: Re: [Avila] watchdog on avila (GW-2348)

Tim Harvey wrote:
> For my use I wrote a driver for the 2347/2348 boards that implemented the
> standard watchdog API but then realized that the typical 1sec heartbeat
from
> userspace was typically not enough to keep the watchdog tickled reliably
so I
> implemented a heartbeat in my driver.  I still ended up with issues on
certain
> kernel versions during certain system calls where the timer in my kernel
driver
> was not getting enough attention.

Could you post the source to your driver?  Maybe Gateworks could include 
this in their next BSP release so that we can use the hardware needed to 
have a working watchdog. My "Avila Network Computer Operating Manual" 
does not mention the DS1819 at all but does mention the IXP425's watchdog.

I wish the CPU reset line was tied to the flash reset 
line...interestingly enough I have seen this very same issue with 
another board using the same Intel NOR flash and an XScale.  I dealt 
with it by making my userspace watchdog program try an orderly reboot 
before the hardware one kicked in.  The orderly reboot properly resets 
the flash.  This doesn't handle kernel faults but it catches failures in 
critical userspace programs.  Also, setting the kernel to reboot on 
panic seemed to reset the flash properly (unless the panic was in the 
JFFS2 driver).
-Ack

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