From: Anton Vorontsov <avorontsov@ru.mvista.com>
To: Laurent Pinchart <laurentp@cse-semaphore.com>
Cc: linuxppc-dev@ozlabs.org, Greg Kroah-Hartman <greg@kroah.com>,
linux-usb@vger.kernel.org,
David Brownell <dbrownell@users.sourceforge.net>,
Li Yang <leoli@freescale.com>,
linux-kernel@vger.kernel.org, Timur Tabi <timur@freescale.com>
Subject: Re: [PATCH 1/3] gpiolib: make gpio_to_chip() public
Date: Tue, 19 Aug 2008 18:50:31 +0400 [thread overview]
Message-ID: <20080819145031.GA28616@oksana.dev.rtsoft.ru> (raw)
In-Reply-To: <200808191126.33133.laurentp@cse-semaphore.com>
On Tue, Aug 19, 2008 at 11:26:28AM +0200, Laurent Pinchart wrote:
[...]
> > I didn't say "SOC-specific". I said "SOC-model specific", which
> > means that the driver would be not portable even across QE chips
> > (i.e. MPC8323 vs. MPC8360, you can assume that the "CLK12" function
> > is having same PAR/ODR/DAT/DIR bits).
>
> If I'm not mistaken, the PAR bit is used to select between GPIO and
> dedicated mode by definition. It should be safe to assume that setting
> a GPIO in dedicated mode requires the PAR bit to be set. But as I
> stated above, we can ignore that for now until a hardware use case
> comes up.
One more thing: you're assuming that there is one par bit, but
there are two par bits for QE chips. Which one would you set in
set_dedicated()? ;-)
> > > > > If, for some
> > > > > reason (driver not loaded, ...), no GPIO user shows up for that
> > > > > pin, it will stay configured in dedicated mode.
> > > >
> > > > Yes.
> > > >
> > > > > It might be better to set the PAR bit unconditionally in
> > > >
> > > > Why it might be better?
> > >
> > > Because, as explained a few lines down, the board initialization code
> > > will be able to configure a pin in a known state (PAR not set) at boot
> > > time until a driver requests the pin to be switched to dedicated mode.
> >
> > You can do this as I described above. But prior to this, yes, you have
> > to configure the pins and let Linux save these values. There is no other
> > way to pass this information, unfortunately.
>
> Ok.
>
> I started implementing CPM2 dedicated mode support to be used in the
> CPM UART driver for RTS/CTS flow control, and soon realized there was
> a show stopper. The CPM UART driver is mostly CPM1/CPM2 agnostic.
> I can't use a function such as cpm2_gpio32_set_dedicated, as that
> wouldn't work on a CPM1 (at least not on all its ports). I could call
> the right function depending on which port the GPIO is on, but that's
> really hackish and would defeat the purpose of using GPIOs.
You can easily refactor cpm gpio code so that you'll have
common cpm structure with platform-specific "GPIO API extension"
callbacks. Something like this:
/*
* generic structure, does not know anything about cpm1/2/qe, or
* ports width.
*/
struct cpm_gpio_chip {
struct of_mm_gpio_chip mm_gc;
spinlock_t lock;
void (*set_dedicated)(unsigned int gpio);
};
struct cpm1_gpio16_chip {
struct cpm_gpio_chip cpgc;
/* shadowed data register to clear/set bits safely */
u16 cpdata;
};
void cpm_gpio_set_dedicated(unsigned int gpio)
{
struct gpio_chip *gc = gpio_to_chip(gpio);
struct of_gpio_chip *ofgc = to_of_gpio_chip(gc);
struct cpm_gpio_chip *cpgc = to_cpm_gpio_chip(ofgc);
if (cpgc->set_dedicated)
cpgc->set_dedicated(gc->base - gpio);
}
> What we
> really need there is a set_dedicated/set_option/set_whatever function
> in the GPIO API :-/
Won't happen. ;-)
--
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2
next prev parent reply other threads:[~2008-08-19 14:50 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-08 16:17 [PATCH 0/3] Patches to support QE USB Host Controller Anton Vorontsov
2008-08-08 16:18 ` [PATCH 1/3] gpiolib: make gpio_to_chip() public Anton Vorontsov
2008-08-14 14:04 ` Laurent Pinchart
2008-08-14 14:14 ` Anton Vorontsov
2008-08-14 14:45 ` Laurent Pinchart
2008-08-14 15:10 ` Anton Vorontsov
2008-08-18 13:58 ` Laurent Pinchart
2008-08-18 14:33 ` Anton Vorontsov
2008-08-18 14:44 ` Laurent Pinchart
2008-08-18 15:33 ` Anton Vorontsov
2008-08-19 9:26 ` Laurent Pinchart
2008-08-19 14:50 ` Anton Vorontsov [this message]
2008-08-08 16:18 ` [PATCH 2/3] powerpc/qe: new call to revert a gpio to a dedicated function Anton Vorontsov
2008-08-08 16:18 ` [PATCH 3/3] USB: driver for Freescale QUICC Engine USB Host Controller Anton Vorontsov
2008-08-08 23:26 ` [PATCH 0/3] Patches to support QE " Greg KH
2008-08-26 15:49 ` Anton Vorontsov
2008-08-14 12:15 ` Laurent Pinchart
2008-09-24 20:04 ` David Brownell
2008-09-18 15:16 Anton Vorontsov
2008-09-18 15:17 ` [PATCH 1/3] gpiolib: make gpio_to_chip() public Anton Vorontsov
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