linux-kernel - RE: basic_mmio_gpio: Add hook for simple debounce register

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Date:	Wed, 16 Nov 2011 16:41:11 -0600
From:	H Hartley Sweeten <hartleys@...ionengravers.com>
To:	Anton Vorontsov <cbouatmailru@...il.com>
CC:	Linux Kernel <linux-kernel@...r.kernel.org>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"jamie@...ieiles.com" <jamie@...ieiles.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"rmk+kernel@....linux.org.uk" <rmk+kernel@....linux.org.uk>
Subject: RE: basic_mmio_gpio: Add hook for simple debounce register

On Wednesday, November 16, 2011 2:40 PM, Anton Vorontsov wrote:
> 
> Hello,
> 
> On Wed, Nov 16, 2011 at 12:02:15PM -0700, H Hartley Sweeten wrote:
>> Some platforms using the basic memory-mapped GPIO library have
>> simple input debounce support that is enabled/disabled, per-input,
>> by setting/clearing bits in a control register. Add a hook in the
>> bgpio_chip structure to hold the void __iomem * for this register.
>> 
>> This register, and the gc.set_debounce callback should set by the
>> platform after calling bgpio_init() and before calling gpiochip_add().
>
> I think it is possible to add 'reg_db' into the device-specific
> (private) structure, so no need to add it into the generic one
> (the fact that the generic gpio code does not use it at all, is a
> sign that you should place it into a private struct).

Good point.

I'm working on converting the gpio-ep93xx driver's interrupt support
over to genirq.  The debounce register was the only thing hanging this
up.

> I.e. something like this:
> 
> struct foo_chip {
> 	struct bgpio_chip bgc;
> 	void __iomem *reg_db;
> };
> 
> static struct foo_chip *to_foo_chip(struct bgpio_chip *bgc)
> {
> 	return container_of(bgc, struct foo_chip, bgc);
> }
> 
> static void foo_gpio_set_debounce(struct gpio_chip *gc, ...)
> {
> 	struct bgpio_chip *bgc = to_bgpio_chip(gc);
> 	struct foo_chip *fgc = to_foo_chip(bgc);
> 
> 	writel(..., fgc->reg_db);
> }
> 
> 
> Or, if the generic code will use that register, then please introduce
> the code at the same time you introduce reg_db.

Currently the reg_db usage is outside the generic code.

I'll modify the gpio-ep93xx driver using something like you have shown
above.  If it looks reasonable to add to gpio-generic we can move it later.

Thanks,
Hartley