ARM: dts: OMAP: Add timer nodes

Add the 12 GP timers nodes present in OMAP2.
Add the 12 GP timers nodes present in OMAP3.
Add the 11 GP timers nodes present in OMAP4.
Add the 7 GP timers nodes present in AM33xx.

Add documentation for timer properties specific to OMAP.

Please note that for OMAP2/3 devices, there is only one interrupt controller
for the ARM CPU (which has the label "intc") and so globally define this as the
interrupt parent to save duplicating the interrupt parent for all device nodes.

Thanks to Vaibhav Hiremath for creating the AM33xx timer nodes. I have modified
Vaibhav's original nodes adding information on which timers support a PWM
output.

Cc: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
ARM: OMAP3: Dynamically disable secure timer nodes for secure 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).

For OMAP3 devices there are 12 general purpose timers available. On secure
devices the 12th timer is reserved for secure usage and so cannot be used by
the kernel, where as for a GP device it is available. We can detect the OMAP
device type, secure or GP, at runtime via an on-chip register. Today, when not
using DT, we do not register the 12th timer as a linux device if the device is
secure.

When using device tree, device tree is going to register all the timer devices
it finds in the device tree blob. To prevent device tree from registering 12th
timer on a secure OMAP3 device we can add a status property to the timer
binding with the value "disabled" at boot time. Note that timer 12 on a OMAP3
device has a property "ti,timer-secure" to indicate that it will not be
available on a secure device and so for secure OMAP3 devices, we search for
timers with this property and then disable them. Using the prom_add_property()
function to dynamically add a property was a recommended approach suggested by
Rob Herring [1].

I have tested this on an OMAP3 GP device and faking it to pretend to be a
secure device to ensure that any timers marked with "ti,timer-secure" are not
registered on boot. I have also made sure that all timers are registered as
expected on a GP device by default.

[1] http://comments.gmane.org/gmane.linux.ports.arm.omap/79203

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. System timer resources (memory and interrupts) are directly obtained from
   the device-tree timer node when booting with device-tree, so that system
   timers are no longer reliant upon the OMAP HWMOD framework to provide these
   resources.

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

4. 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".

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

6. 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>