[PATCH] arm: omap2: Kconfig: select TWD and global timer on AM43xx devices

On 11/18/2015 6:33 AM, Grygorii Strashko wrote:

On 11/13/2015 06:39 PM, santosh shilimkar wrote:

quoted

On 11/13/2015 5:07 AM, Mason wrote:

quoted

On 13/11/2015 13:48, Grygorii Strashko wrote:

quoted

On 11/12/2015 08:06 PM, Felipe Balbi wrote:

quoted

Make sure to tell the kernel that AM437x has
TWD and global timers.

Signed-off-by: Felipe Balbi <redacted>
---

Hi Tony,

now that all dependencies are in place, we can
finally enable twd and global_timer for AM437x.

Is AM437x SMP SOC ?

No. But it has ARM TWD and GT

quoted

Is TWD on AM437x works in low power states ?

No. But TWD, seems, is not a problem here if omap gp timer
can be used as broadcast device.

quoted

Probably I haven't followed the recent updates, but does
the TWD supports C3STOP on UP systems ? The broadcast
code was SMP only in past, and TWD use to die in
low power state on past OMAP SOCs.

If either of these are still the issue then
TWD shouldn't be used.

Yep. I see the problem with ARM Global timer here if
CPUIdle is enabled and ARM Global timer is selected as
clocksource device.

Its expected and well known limitation.

I think, it will be right thing to disable "global_timer"
and "local_timer" nodes in am437x.dtsi by default - if
someone would like to use them then those nodes have
to be enabled explicitly in board file.
(TWD timer will be enabled on OMAP multi SoC build
  irrespectively of HAVE_ARM_TWD is selected for am437x or not,
  because it will be selected for omap4).
I've just sent corresponding patch:
  http://www.spinics.net/lists/arm-kernel/msg461141.html

Also, probably, it could be reasonable to:
- make ARM_GLOBAL_TIMER fully selectable option and allow select it from defconfig.

- or - update this patch as below
-       select ARM_GLOBAL_TIMER
-       select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
+       select ARM_GLOBAL_TIMER if !CPU_IDLE
+       select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK if ARM_GLOBAL_TIMER

+1