linux-kernel - Re: [PATCH 1/3 v3] pinctrl: ADI PIN control driver for the GPIO controller on bf54x and bf60x.

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Date:	Thu, 29 Aug 2013 10:12:45 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Sonic Zhang <sonic.adi@...il.com>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Grant Likely <grant.likely@...aro.org>,
	Steven Miao <realmz6@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	adi-buildroot-devel@...ts.sourceforge.net,
	Sonic Zhang <sonic.zhang@...log.com>
Subject: Re: [PATCH 1/3 v3] pinctrl: ADI PIN control driver for the GPIO
 controller on bf54x and bf60x.

On Thu, Aug 22, 2013 at 9:07 AM, Sonic Zhang <sonic.adi@...il.com> wrote:

> There are 6 to 9 GPIO HW blocks in one Blackfin SoC. Function
> pinmux_enable_setting() in current pinctrl framework assumes the
> function mux setting of one peripheral pin group is configured in one
> pinctrl device. But, the function mux setting of one blackfin
> peripheral may be done among different GPIO HW blocks. So, I have to
> separate the pinctrl driver from the GPIO block driver add the ranges
> of all GPIO blocks into one pinctrl device for Blackfin.

This is similar to the situation in the pinctrl-nomadik.c driver,
where the pinctrl portions wait for the GPIO devices to instantiate
before proceeding to probe "on top" of the GPIO blocks, using
the latter to get to the registers.

I am not sure we have found the best way to sort out this
type of system, let's see what we can come up with.

One way I was contemplating was to have just one fat node
in the device tree containing all the register ranges, and one
fat probe function, so all these ranges associated with a
single struct device, but that does not well work with
clocking and interrupts (the GPIO ranges needed one
clock and interrupt each) so I gave up on that idea.

My latest idea was to to to break the subsystems apart a
bit by letting GPIO devices probe without the underlying
pin controller being in place, so I queued up the operations
until the pin controller arrived, but unfortunately this creates
other problems :-(

Still this creates a fuzz when trying to refactor stuff so we
need to find a solution.

Yours,
Linus Walleij
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