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

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Message-ID: <540067A1.6090005@rock-chips.com>
Date:	Fri, 29 Aug 2014 19:44:33 +0800
From:	Huang Tao <huangtao@...k-chips.com>
To:	Mark Rutland <mark.rutland@....com>
CC:	Kever Yang <kever.yang@...k-chips.com>,
	"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>,
	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 <Lorenzo.Pieralisi@....com>
Subject: Re: [RESEND PATCH] ARM: dts: make arch-timer always on in rk3288
 soc

Hi,

在 2014年08月29日 19:22, Mark Rutland 写道:
>> 在 2014年08月28日 23:11, Mark Rutland 写道:
>>> To clarify: if there are low power states that the CPU can enter where
>>> we lose state, then this patch isn't correct.
>> Right now, the software of RK3288 SoC only support CPU hotplug
>> (cpu_on/off) and power off all CPUs on suspend.
> Sure, but that's a Linux implementation detail rather than a fixed
> property of the hardware. Given those states exist, the "always-on"
> property is not appropriate.
>
>> We do not implement cpuidle to power off CPU. Do you think we should
>> introduce a broadcast timer?
> If one is present, yes. 
>
>> On our early kernel, I never see any interrupt on a broadcast timer
>> (yes, we implement it with a external timer).
> That's fine; Linux doesn't need to use it just yet. However, when we
> want to use low power states later, it will be necessary to enable
> placing all CPUS into a low power state.
>
> If your external timer is already supported by an existing driver, there
> is no reason not to add it now.
>
>>> A more general approach would be to enable the broadcast hrtimer for
>>> arm, as has been done for arm64.
>> Yes. I think it should be done by arm framework.
> Patches welcome.
>
> I also think it would make sense to enable this for arm.
>
> Thanks,
> Mark.
>
>
Okay, so this patch is wrong as I expected.
Thank you!

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