linux-kernel - Re: [PATCH 01/11] mfd: add the Berlin controller driver

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Date:	Wed, 18 Feb 2015 14:09:04 +0100
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Lee Jones <lee.jones@...aro.org>
CC:	Antoine Tenart <antoine.tenart@...e-electrons.com>,
	sameo@...ux.intel.com, jszhang@...vell.com, zmxu@...vell.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	arnd@...db.de
Subject: Re: [PATCH 01/11] mfd: add the Berlin controller driver

On 02/18/2015 12:58 PM, Lee Jones wrote:
> I do agree that using 'simple-bus' to describe only this IP would be
> an abuse.  However, my foundation thought/argument is unchanged.  This
> 'driver' is a hack.  It has no functional use besides to work around a
> problem of semantics and as such has no place in MFD.

Lee,

sorry I don't get it. Here you say that using simple-bus is an abuse...

> Back onto the simple-bus theme, as this is a syscon device it is a bus
> of sorts.  Have you thought about making it a child of your its syscon
> node, then using simple-bus to get the OF framework to register the
> child devices?

... and here you suggest to use simple-bus to register the child
devices?

I fundamentally disagree that either this registers or syscon in general
should in any way be seen as a bus. The chip control registers is an
highly unsorted bunch of bits that we try to match with cleanly
separated subsystems. This makes it a resource but no bus of any sort.

The problem that we try to solve here is not a DT problem but solely
driven by the fact that we need something to register platform_devices
for pinctrl and reset. The unit we describe in DT is a pinctrl-clock-
power-reset-unit - or short chip control.

If you argue that mfd is not the right place for this "driver" we'll
have to find a different place for it. I remember Mike has no problem
with extending early probed clock drivers to register additional
platform_devices - so I guess we end up putting it in there ignoring
mfd's ability to do it for us.

Do we agree on that?

Sebastian
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