linux-imx

ARM: OMAP3: Update clocksource timer selection

When booting with device-tree for OMAP3 and AM335x devices and a gptimer
is used as the clocksource (which is always the case for AM335x), a
gptimer located in a power domain that is not always-on is selected.
Ideally we should use a gptimer for clocksource that is located in a
power domain that is always on (such as the wake-up domain) so that time
can be maintained during a kernel suspend without keeping on additional
power domains unnecessarily.

In order to fix this so that we can select a gptimer located in a power
domain that is always-on, the following changes were made ...
1. Currently, only when selecting a gptimer to use for a clockevent
   timer, do we pass a timer property that can be used to select a
   specific gptimer. Change this so that we can pass a property when
   selecting a gptimer to use for a clocksource timer too.
2. Currently, when selecting either a gptimer to use for a clockevent
   timer or a clocksource timer and no timer property is passed, then
   the first available timer is selected regardless of the properties
   it has. Change this so that if no properties are passed, then a timer
   that does not have additional features (such as always-on, dsp-irq,
   pwm, and secure) is selected.

For OMAP3 and AM335x devices that use a gptimer for clocksource, change
the selection of the gptimer so that by default the gptimer located in
the always-on power domain is used for clocksource instead of
clockevents.

Please note that using a gptimer for both clocksource and clockevents
can have a system power impact during idle. The reason being is that
OMAP and AMxxx devices typically only have one gptimer in a power domain
that is always-on. Therefore when the kernel is idle both the clocksource
and clockevent timers will be active and this will keep additional power
domains on. During kernel suspend, only the clocksource timer is active
and therefore, it is better to use a gptimer in a power domain that is
always-on for clocksource.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>