Some boards want to change low power state of pins on-the-fly, this
function helps to facilitate that operation instead of switching
back-n-forth between two configurations with pxa2xx_mfp_config().
Signed-off-by: NEric Miao <eric.miao@marvell.com>
Tested-by: NRobert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Changes include:

1. rename MFP_LPM_WAKEUP_ENABLE into MFP_LPM_CAN_WAKEUP to indicate
   the board capability of this pin to wakeup the system

2. add gpio_set_wake() and keypad_set_wake() to allow dynamically
   enable/disable wakeup from GPIOs and keypad GPIO

   * these functions are currently kept in mfp-pxa2xx.c due to their
     dependency to the MFP configuration

3. pxa2xx_mfp_config() only gives early warning if MFP_LPM_CAN_WAKEUP
   is set on incorrect pins

So that the GPIO's wakeup capability is now decided by the following:

   a) processor's capability: (only those GPIOs which have dedicated
      bits within PWER/PRER/PFER can wakeup the system), this is
      initialized by pxa{25x,27x}_init_mfp()

   b) board design decides:
      - whether the pin is designed to wakeup the system (some of
        the GPIOs are configured as other functions, which is not
        intended to be a wakeup source), by OR'ing the pin config
        with MFP_LPM_CAN_WAKEUP

      - which edge the pin is designed to wakeup the system, this
        may depends on external peripherals/connections, which is
        totally board specific; this is indicated by MFP_LPM_EDGE_*

   c) the corresponding device's (most likely the gpio_keys.c) wakeup
      attribute:
Signed-off-by: Neric miao <eric.miao@marvell.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Pin configuration on pxa{25x,27x} has now separated from generic GPIO
into dedicated mfp-pxa2xx.c by this patch. The name "mfp" is borrowed
from pxa3xx and is used here to alert the difference between the two
concepts: pin configuration and generic GPIOs.  A GPIO can be called
a "GPIO" _only_ when the corresponding pin is configured so.

A pin configuration on pxa{25x,27x} is composed of:

    - alternate function selection (or pin mux as commonly called)
    - low power state or sleep state
    - wakeup enabling from low power mode

The following MFP_xxx bit definitions in mfp.h are re-used:

    - MFP_PIN(x)
    - MFP_AFx
    - MFP_LPM_DRIVE_{LOW, HIGH}
    - MFP_LPM_EDGE_*

Selecting alternate function on pxa{25x, 27x} involves configuration
of GPIO direction register GPDRx, so a new bit and MFP_DIR_{IN, OUT}
are introduced. And pin configurations are defined by the following
two macros:

    - MFP_CFG_IN  : for input alternate functions
    - MFP_CFG_OUT : for output alternate functions

Every configuration should provide a low power state if it configured
as output using MFP_CFG_OUT().  As a general guideline, the low power
state should be decided to minimize the overall power dissipation. As
an example, it is better to drive the pin as high level in low power
mode if the GPIO is configured as an active low chip select.

Pins configured as GPIO are defined by MFP_CFG_IN(). This is to avoid
side effects when it is firstly configured as output.  The actual
direction of the GPIO is configured by gpio_direction_{input, output}

Wakeup enabling on pxa{25x, 27x} is actually GPIO based wakeup, thus
the device based enable_irq_wake() mechanism is not applicable here.

E.g.  invoking enable_irq_wake() with a GPIO IRQ as in the following
code to enable OTG wakeup is by no means portable and intuitive, and
it is valid _only_ when GPIO35 is configured as USB_P2_1:

    enable_irq_wake( gpio_to_irq(35) );

To make things worse, not every GPIO is able to wakeup the system.
Only a small number of them can, on either rising or falling edge,
or when level is high (for keypad GPIOs).

Thus, another new bit is introduced to indicate that the GPIO will
wakeup the system:

    - MFP_LPM_WAKEUP_ENABLE

The following macros can be used in platform code, and be OR'ed to
the GPIO configuration to enable its wakeup:

    - WAKEUP_ON_EDGE_{RISE, FALL, BOTH}
    - WAKEUP_ON_LEVEL_HIGH

The WAKEUP_ON_LEVEL_HIGH is used for keypad GPIOs _only_, there is
no edge settings for those GPIOs.

These WAKEUP_ON_* flags OR'ed on wrong GPIOs will be ignored in case
that platform code author is careless enough.

The tradeoff here is that the wakeup source is fully determined by
the platform configuration, instead of enable_irq_wake().
Signed-off-by: Neric miao <eric.miao@marvell.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>