From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Subject: Re: [RESEND PATCH] ARM: dts: make arch-timer always on in rk3288 soc Date: Fri, 29 Aug 2014 12:22:42 +0100 Message-ID: <20140829112242.GC21473@leverpostej> References: <1409190017-12656-1-git-send-email-kever.yang@rock-chips.com> <20140828091758.GB14650@leverpostej> <20140828151121.GM14650@leverpostej> <53FFEE40.3010001@rock-chips.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <53FFEE40.3010001-TNX95d0MmH7DzftRWevZcw@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Huang Tao Cc: Kever Yang , "heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org" , "dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org" , "sonnyrao-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org" , "addy.ke-TNX95d0MmH7DzftRWevZcw@public.gmane.org" , "cf-TNX95d0MmH7DzftRWevZcw@public.gmane.org" , "xjq-TNX95d0MmH7DzftRWevZcw@public.gmane.org" , "wulf-TNX95d0MmH7DzftRWevZcw@public.gmane.org" , "lyz-TNX95d0MmH7DzftRWevZcw@public.gmane.org" , "hj-TNX95d0MmH7DzftRWevZcw@public.gmane.org" , Rob Herring , Pawel Moll , Ian Campbell , Kumar Gala , Russell King , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Lorenzo Pieralisi List-Id: devicetree@vger.kernel.org On Fri, Aug 29, 2014 at 04:06:40AM +0100, Huang Tao wrote: > Hi, Mark: Hi, > =E5=9C=A8 2014=E5=B9=B408=E6=9C=8828=E6=97=A5 23:11, Mark Rutland =E5= =86=99=E9=81=93: > > To clarify: if there are low power states that the CPU can enter wh= ere > > 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.=20 > 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, ther= e is no reason not to add it now. > > A more general approach would be to enable the broadcast hrtimer fo= r > > 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 devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html