linux-kernel - Re: [RESEND PATCH] ARM: dts: make arch-timer always on in rk3288 soc

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Message-ID: <53FFCAC4.7030702@rock-chips.com>
Date:	Fri, 29 Aug 2014 08:35:16 +0800
From:	Kever Yang <kever.yang@...k-chips.com>
To:	Mark Rutland <mark.rutland@....com>
CC:	"heiko@...ech.de" <heiko@...ech.de>,
	"dianders@...omium.org" <dianders@...omium.org>,
	"sonnyrao@...omium.org" <sonnyrao@...omium.org>,
	"addy.ke@...k-chips.com" <addy.ke@...k-chips.com>,
	"cf@...k-chips.com" <cf@...k-chips.com>,
	"xjq@...k-chips.com" <xjq@...k-chips.com>,
	"wulf@...k-chips.com" <wulf@...k-chips.com>,
	"lyz@...k-chips.com" <lyz@...k-chips.com>,
	"hj@...k-chips.com" <hj@...k-chips.com>,
	"huangtao@...k-chips.com" <huangtao@...k-chips.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	lorenzo.pieralisi@....com
Subject: Re: [RESEND PATCH] ARM: dts: make arch-timer always on in rk3288
 soc

Mark,

     Thanks for your reply and advice.

On 08/28/2014 11:11 PM, Mark Rutland wrote:
> On Thu, Aug 28, 2014 at 10:17:58AM +0100, Mark Rutland wrote:
>> Hi Kever,
>>
>> On Thu, Aug 28, 2014 at 02:40:17AM +0100, Kever Yang wrote:
>>> We need use the hrtimer, which need the arch-timer to be 'always-on'
>> I asked a question on the last posting [1]. Can you please confirm
>> either way?
>>
>> Thanks,
>> Mark.
>>
>> [1] lists.infradead.org/pipermail/linux-arm-kernel/2014-August/282327.html
> To clarify: if there are low power states that the CPU can enter where
> we lose state, then this patch isn't correct.
rk3288 has low power state and may turn off the cpu power domain
which will lost any logic state in cpu.
>
> A more general approach would be to enable the broadcast hrtimer for
> arm, as has been done for arm64.
>
> See commit 5d1638acb9f6 (tick: Introduce hrtimer based broadcast) which
> introduced the broadcast hrtimer, and commit 9358d755bd5c (arm64:
> kernel: initialize broadcast hrtimer based clock event device) which
> added the requisite plumbing for arm64.
I'll going to implement this and send another patch.

Thanks.

-Kever

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