arm/dts: OMAP: Add timer nodes

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

Add documentation for timer properties specific to OMAP.

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: OMAP4: Add timer clock aliases for device-tree

For OMAP4, the dmtimers are located in the Wake-up, ABE and Peripheral (PER)
power domains. Hence, when the dmtimer is configured to use the "timer_sys_ck"
as its functional clock the actual clock used is different depending on whether
the clock is in the Wake-up, ABE or PER domain. So when we look-up the dmtimer's
"timer_sys_ck" we need to specify the timer device name as well as clock alias
to find the right clock.

Currently, the device names for the timers have the format "omap_timer.X" where
X is the timer instance number. When using to device tree, the format of the
device name created by device-tree is different and has the format
"<reg-address>.<device-name>" (this is assuming that the device-tree "reg"
property is specified). This causes the look-up for the OMAP4 "timer_sys_ck" to
fail. To fix this add new timer clock alias for using device-tree.

Please note that adding a 2nd set of clock aliases for the same clocks to only
temporary until device-tree migration is complete. Then we can remove the legacy
aliases. Hence, I have marked the legacy aliases with a "TODO" to remove them.

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: 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: 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.

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 and will return an error if called when device-tree is
       present. Users of this API should instead use
       omap_dm_timer_request_by_cap().
   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 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
   Search for the above parameters and set the appropriate timer attribute
   flags.

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