Subject: Re: [PATCH] powerpc/mpc52xx/wdt: Fix 5200 wdt always being used as gpt

From: Albrecht Dreß <[email-masked]>
Date: Mon, 03 Aug 2009 20:46:38 +0200

Am 03.08.09 19:50 schrieb(en) Grant Likely:
> Just about all mpc5200 device trees have the fsl,has-wdt property on  
> GPT0 even when it isn't used as a watchdog.

Sorry, I do not understand...  The file  
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt says

<snip>
On the mpc5200 and 5200b, GPT0 has a watchdog timer function.  If the  
board design supports the internal wdt, then the device node for GPT0  
should include the empty property 'fsl,has-wdt'.
</snip>

I interpreted this as "if you don't want to have the wdt function of  
gpt0, remove this property".  If this assumption is wrong, how is the  
kernel supposed to decide if a device shall be used as gpt or as wdt?

> The boards using GPT0 as a GPIO or timer will be broken by this patch.

A wdt is a security device which will (IMHO) either not be used as  
such, or it is a *must not* be used for something else on a particular  
board (you may even want u-boot to activate it, e.g. to detect a  
hanging boot process).  In both cases, a "tuned" device tree is needed.

> I know it is a lot more work, but the correct solution is to merge  
> the GPT watchdog driver into the regular GPT driver so that we don't  
> have two device drivers trying to bind against the same device.

I see the benefit of removing some duplicate code and of having gpio  
access in parallel with the wdt, but it wouldn't solve the general  
confusion above!  Will look into that, though...

Best, Albrecht.