[PATCH] arm: omap2: Kconfig: select TWD and global timer on AM43xx devices
santosh.shilimkar at oracle.com
Wed Nov 18 10:01:17 PST 2015
On 11/18/2015 6:33 AM, Grygorii Strashko wrote:
> On 11/13/2015 06:39 PM, santosh shilimkar wrote:
>> On 11/13/2015 5:07 AM, Mason wrote:
>>> On 13/11/2015 13:48, Grygorii Strashko wrote:
>>>> On 11/12/2015 08:06 PM, Felipe Balbi wrote:
>>>>> Make sure to tell the kernel that AM437x has
>>>>> TWD and global timers.
>>>>> Signed-off-by: Felipe Balbi <balbi at ti.com>
>>>>> 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
>> 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.
>> 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:
> 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
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