ARM: OMAP: Add a timer attribute for timers that can interrupt the DSP

Some instances of the DMTIMER peripheral on OMAP devices have the ability
to interrupt the on-chip DSP in addition to the ARM CPU. Add a DMTIMER
attribute to indicate which timers can interrupt the DSP. By using the
omap_dm_timer_request_by_cap() API, driver will now be able to allocate
a DMTIMER that can interrupt the DSP based upon this attribute and not require
the driver to know which instance has this capability.

DMTIMERs that have the ability to interrupt the DSP on OMAP devices are as
follows ...

- OMAP1 (OMAP5912/16xx/17xx) devices	- All 8 DMTIMERs
- OMAP2/3/4 devices			- DMTIMERs 5-8

Please note that for OMAP3+, timer8 has the ability to interrupt the DSP and
generate a PWM output.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
ARM: OMAP: Add function to request a timer by capability

Currently OMAP timers can be requested by requesting any available or by a
numerical device ID. If a specific timer is required because it has a particular
capability, such as can interrupt the on-chip DSP in addition to the ARM CPU,
then the user needs to know the device ID of the timer with this feature.
Therefore, add a new API called omap_dm_timer_request_by_cap() that allows
drivers to request a timer by capability.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
ARM: OMAP3: Add generic machine descriptor for boards with OMAP3 GP devices

OMAP3 devices may or may not have security features enabled. Security enabled
devices are known as high-secure (HS) and devices without security are known as
general purpose (GP).

Some OMAP3 boards, such as the OMAP3 beagle board, only use GP devices and for
GP devices there is a 12th timer available on-chip that can operate at 32kHz.
The clock for 12th timer is generated by an internal oscillator and is unique
this timer. Boards such as the beagle board use this timer as a 32kHz based
clock-events timer because early versions of the board had a hardware problem
preventing them from using other on-chip timers clocked by a external 32kHz
clock.

When booting with device-tree all OMAP3 devices use timer 1 by default for
the clock-events timer. Therefore, add a generic machine descriptor for boards
with OMAP3 GP devices so that they can use the 12th timer as the clock-events
timer instead of the default.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
ARM: OMAP: Add DT support for timer driver

In order to add device-tree support to the timer driver the following changes
were made ...

1. Allocate system timers (used for clock-events and clock-source) based upon
   timer properties rather than using an hard-coded timer instance ID. To allow
   this a new helper function called omap_dmtimer_find_by_property() has been
   added for finding a timer with the particular properties in the device-tree
   blob. Please note that this is an internal helper function for system timers
   only to find a timer in the device-tree blob. This cannot be used by device
   drivers, another API has been added for that (see below). Timers that are
   allocated for system timers are dynamically disabled at boot time by adding
   a status property with the value "disabled" to the timer's device-tree node.

   Please note that when allocating system timers we now pass a timer ID and
   timer property. The timer ID is only be used for allocating a timer when
   booting without device-tree. Once device-tree migration is complete, all
   the timer ID references will be removed.

2. If DT blob is present, then let device-tree create the timer devices
   dynamically.

3. When device-tree is present the "id" field in the platform_device structure
   (pdev->id) is initialised to -1 and hence cannot be used to identify a timer
   instance. Due to this the following changes were made ...
   a). The API omap_dm_timer_request_specific() is not supported when using
       device-tree, because it uses the device ID to request a specific timer.
       This function will return an error if called when device-tree is present.
       Users of this API should use omap_dm_timer_request_by_cap() instead.
   b). When removing the DMTIMER driver, the timer "id" was used to identify the
       timer instance. The remove function has been modified to use the device
       name instead of the "id".

4. When device-tree is present the platform_data structure will be NULL and so
   check for this.

5. The OMAP timer device tree binding has the following optional parameters ...
   a). ti,timer-alwon  --> Timer is in an always-on power domain
   b). ti,timer-dsp    --> Timer can generate an interrupt to the on-chip DSP
   c). ti,timer-pwm    --> Timer can generate a PWM output
   d). ti,timer-secure --> Timer is reserved on a secure OMAP device
   Search for the above parameters and set the appropriate timer attribute
   flags.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>