linux-kernel - Re: [PATCH v3] watchdog: Add watchdog timer support for the WinSystems EBC-C384

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Date:	Wed, 27 Jan 2016 17:51:50 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	William Breathitt Gray <vilhelm.gray@...il.com>, wim@...ana.be
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] watchdog: Add watchdog timer support for the
 WinSystems EBC-C384

On 01/27/2016 04:18 PM, William Breathitt Gray wrote:
> On Tue, Jan 26, 2016 at 09:02:45PM -0800, Guenter Roeck wrote:
>>> Unfortunately, the sensors-detect only reported "No" for each Super I/O
>>> chip test, while the superiotool gave an unhelpful "No Super I/O chip
>>> detected" message.
>>>
>>
>> Too bad. That suggests that the watchdog may in fact be implemented in the fpga.
>
> I received a response from WinSystems: the watchdog timer is implemented
> in the Lattice FPGA (base address 0x298), along with other WinSystems
> firmware. I was offered two methods of identifying the chip.
>
> The first method is to use a 16-bit read of the register at port address
> 0x29E to get the version number of the watchdog timer; my machine
> reported a value of 0x0009. Unfortunately, I don't believe this method
> is very reliable since the version number may not be consistent across
> these motherboards, and the same value could easily happen to be
> returned by an unknown hardware.
>
> The second method is slightly more involved so I'll quote WinSystems:
>
>> 8-bit read of 299h – save this value
>> 8-bit write of 60h to 299h
>> 16-bit read of 29ah should return the base address of the WDT which is 564h
>> 8-bit write of saved value to 299h - don’t want t accidentally change the WDT base address
>
> If the system does return a value of 0x564, then it's pretty safe to say
> that the watchdog timer is implemented on the chip. However, I'm not
> sure it would be safe to send write commands to a port address until the
> hardware has been identified; this second method may not be the best
> route either.
>
> What do you think?
>
Let's stick with DMI.

Thanks,
Guenter