From: santosh.shilimkar@oracle•com (santosh shilimkar)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arm: omap2: Kconfig: select TWD and global timer on AM43xx devices
Date: Wed, 18 Nov 2015 10:01:17 -0800 [thread overview]
Message-ID: <564CBCED.2010906@oracle.com> (raw)
In-Reply-To: <564C8C41.9080006@ti.com>
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@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:
> 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
next prev parent reply other threads:[~2015-11-18 18:01 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-12 18:06 [PATCH] arm: omap2: Kconfig: select TWD and global timer on AM43xx devices Felipe Balbi
2015-11-13 12:48 ` Grygorii Strashko
2015-11-13 13:07 ` Mason
2015-11-13 16:39 ` santosh shilimkar
2015-11-18 14:33 ` Grygorii Strashko
2015-11-18 18:01 ` santosh shilimkar [this message]
2015-11-13 17:15 ` Grygorii Strashko
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