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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140829112242.GC21473@leverpostej>
Date:	Fri, 29 Aug 2014 12:22:42 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Huang Tao <huangtao@...k-chips.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

On Fri, Aug 29, 2014 at 04:06:40AM +0100, Huang Tao wrote:
> Hi, Mark:

Hi,

> 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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/