[PATCH] ARM: pxa: mfp: Force gpio direction for MFP_LPM_KEEP_OUTPUT

[Paul Parsons]

Hello Igor,

--- On Sun, 1/4/12, Igor Grinberg <grinberg at compulab.co.il> wrote:
> Hi Paul,
> 
> On 03/31/12 15:20, Paul Parsons wrote:
> > Some MFP configurations specify MFP_LPM_KEEP_OUTPUT to
> preserve the gpio output
> > value (HIGH or LOW) during sleep mode. For example:
> > 
> >     GPIO72_GPIO |
> MFP_LPM_KEEP_OUTPUT,
> > 
> > Unfortunately MFP_LPM_KEEP_OUTPUT makes no special
> provision for setting the
> > sleep mode gpio direction, unlike MFP_LPM_DRIVE_HIGH
> and MFP_LPM_DRIVE_LOW.
> > Consequently MFP configurations of the form:
> > 
> >     GPIO<n>_GPIO |
> MFP_LPM_KEEP_OUTPUT,
> > 
> > will set the sleep mode gpio direction to INPUT.
> > 
> > This patch forces the sleep mode gpio direction to
> OUTPUT in cases where
> > MFP_LPM_KEEP_OUTPUT was specified. This brings
> MFP_LPM_KEEP_OUTPUT into line
> > with MFP_LPM_DRIVE_HIGH and MFP_LPM_DRIVE_LOW.
> > 
> > Signed-off-by: Paul Parsons <lost.distance at yahoo.com>
> > ---
> > 
> > diff --git a/arch/arm/mach-pxa/mfp-pxa2xx.c
> b/arch/arm/mach-pxa/mfp-pxa2xx.c
> > index b0a8428..3b443199 100644
> > --- a/arch/arm/mach-pxa/mfp-pxa2xx.c
> > +++ b/arch/arm/mach-pxa/mfp-pxa2xx.c
> > @@ -96,6 +96,9 @@ static int __mfp_config_gpio(unsigned
> gpio, unsigned long c)
> >          break;
> >      }
> >  
> > +    if (c & MFP_LPM_KEEP_OUTPUT)
> > +        is_out = 1;
> > +
> 
> MFP_LPM_KEEP_OUTPUT does not meant to be used to setup the
> mfp config,

As far as I can see, MFP_LPM_KEEP_OUTPUT is *only* used to setup the
mfp config:

% xzcat linux-3.4-rc1.tar.xz | fgrep -a MFP_LPM_KEEP_OUTPUT
	GPIO13_GPIO | MFP_LPM_KEEP_OUTPUT,	/* CORGI_GPIO_LED_ORANGE */
	GPIO38_GPIO | MFP_LPM_KEEP_OUTPUT,	/* CORGI_GPIO_CHRG_ON */
	GPIO43_GPIO | MFP_LPM_KEEP_OUTPUT,	/* CORGI_GPIO_CHRG_UKN */
#define MFP_LPM_KEEP_OUTPUT	(0x1 << 25)
	/* set corresponding PGSR bit of those marked MFP_LPM_KEEP_OUTPUT */
		if ((gpio_desc[i].config & MFP_LPM_KEEP_OUTPUT) &&
% 

> but for pins that have been configured for output by
> gpio_direction_out().
> (Hint: *_KEEP_*).

MFP_LPM_KEEP_OUTPUT only takes effect when the system enters sleep mode,
at which point the GPIO directions (GPDR registers) are forced from the
values privately stored in gpdr_lpm[].
As far as I can tell MFP_LPM_KEEP_OUTPUT has no direct connection to
gpio_direction_output().

> Also, I don't think this is a good idea, because the patch
> allows a pin
> be configured as output, but does not forces a value
> (high/low)
> and this is not safe.

A value does not need to be provided until the system enters sleep mode,
at which point the value is provided via the PGSR registers.

   353	static int pxa2xx_mfp_suspend(void)
   354	{
   355		int i;
   356	
   357		/* set corresponding PGSR bit of those marked MFP_LPM_KEEP_OUTPUT */
   358		for (i = 0; i < pxa_last_gpio; i++) {
   359			if ((gpio_desc[i].config & MFP_LPM_KEEP_OUTPUT) &&
   360			    (GPDR(i) & GPIO_bit(i))) {
   361				if (GPLR(i) & GPIO_bit(i))
   362					PGSR(gpio_to_bank(i)) |= GPIO_bit(i);
   363				else
   364					PGSR(gpio_to_bank(i)) &= ~GPIO_bit(i);
   365			}
   366		}
   367	
   368		for (i = 0; i <= gpio_to_bank(pxa_last_gpio); i++) {
   369	
        ...
   375			GPDR(i * 32) = gpdr_lpm[i];
   376		}
   377		return 0;
   378	}

However looking at pxa2xx_mfp_suspend() more closely it is true that the
GPDR registers are set before the PGSR values take effect (when the
processor enters sleep mode).
That is no different from MFP_LPM_DRIVE_HIGH or MFP_LPM_DRIVE_LOW though.
So the presumption must be that the GPIOs configured as DRIVE_HIGH,
DRIVER_LOW and now KEEP_OUTPUT already have a valid direction and value
set at the point the GPDR registers are forced.

> Why can't you use:
> GPIO<n>_GPIO | MFP_LPM_DRIVE_<level>
> ?

The hx4700 has a couple of charging GPIOs which we want to keep HIGH or
LOW during sleep mode:

% fgrep MFP_LPM_KEEP_OUTPUT arch/arm/mach-pxa/hx4700.c
	GPIO72_GPIO | MFP_LPM_KEEP_OUTPUT,	/* BQ24022_nCHARGE_EN */
	GPIO96_GPIO | MFP_LPM_KEEP_OUTPUT,	/* BQ24022_ISET2 */
% 

Regards,
Paul