linux-kernel - Re: [PATCH v2 0/8] watchdog: w83627hf: Convert to watchdog infrastructure

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Date:	Sat, 23 Mar 2013 13:57:42 +0100
From:	Wim Van Sebroeck <wim@...ana.be>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Pádraig Brady <P@...igBrady.com>
Subject: Re: [PATCH v2 0/8] watchdog: w83627hf: Convert to watchdog infrastructure

Hi Guenter,

> > In 2011 I started something similar but then with the MFD approach in mind.
> > Goal was also to clean-up the w836* watchdog drivers and get a clean driver that
> > supports all Winbond super-I/O based watchdog drivers.
> > 
> > I dug op the development code again. I'll post it in a next e-mail so that we can
> > see what the best way forward is. Note: I took the MFD approach because:
> > 1) all superio shares the similar functions for using the Super-I/O registers.
> > 2) Goal is to have low-level driver that support the specific super-I/O chipsets
> > and that does the platform stuff for hwmon, watchdog, gpio, ...
> > 
> Hi Wim,
> 
> I started with a similar approach, only I used mfd cells to pass on platform
> specific information such as the device type and the superio base address.
> I still have the patchset for the mfd driver, in case you are interested.
> My code is based on the patches submitted by Rodolfo Giometti a couple
> of years ago. Want me to post it ?

If it's not v1 then I am interested.
I think it depends on the super-I/O chipset of what info you can pass. I would
not use mfd cells for the winbond driver but use platform data (similar to
drivers/mfd/adp5520.c) because you don't need more then just pass some data.

> What I noticed in my testing is that the superio address range (2e or 4e),
> which the drivers currently take as granted, is at least on my systems
> (all three of them) reserved by ACPI. Unfortunately that means one can not
> use the mfd infrastructure to pass on the superio memory region,
> since it checks for acpi conflicts. With that I gave up on the idea and
> reverted to using request_muxed_region. That seemed simpler and accomplish
> the same as long as all drivers actually use it.

Noticed the same. That's why passing the platform data together with the
superio-address and type seems the best way to go. I also kept the superio_enter
and superio_exit a function in the low level driver because I used a lock to
make sure that the hwmon code doesn't start doing things when the watchdog is
doing things. But I think that the request_muxed_region is doing something similar
also.

Kind regards,
Wim.

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