From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH v2 00/12] CPU idle for Armada XP Date: Fri, 13 Sep 2013 07:48:05 -0700 Message-ID: <871u4shj6i.fsf@linaro.org> References: <1379066801-16276-1-git-send-email-gregory.clement@free-electrons.com> <20130913110043.GJ19363@lunn.ch> <5232F43D.4040404@free-electrons.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5232F43D.4040404@free-electrons.com> (Gregory CLEMENT's message of "Fri, 13 Sep 2013 13:17:17 +0200") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Gregory CLEMENT Cc: Lior Amsalem , Andrew Lunn , Ike Pan , Atsushi Yamagata , Nadav Haklai , David Marlin , Yehuda Yitschak , Tawfik Bayouk , Dan Frazier , Daniel Lezcano , Eran Ben-Avi , Ezequiel Garcia , Leif Lindholm , Sebastian Hesselbarth , Tomonori Kimura , Jason Cooper , Nobuhiro Iwamatsu , linux-pm@vger.kernel.org, Jon Masters , "Rafael J. Wysocki" , Hironobu Shibata , linux-arm-kernel@lists.infradead.org, Thomas Petazzoni List-Id: linux-pm@vger.kernel.org Gregory CLEMENT writes: > On 13/09/2013 13:00, Andrew Lunn wrote: >> >> On Fri, Sep 13, 2013 at 12:06:29PM +0200, Gregory CLEMENT wrote: >>> Hello, >>> >>> This patch set adds the CPU idle support for Armada XP and prepares >>> the support for Armada 370. This was based on the work of Nadav >>> Haklai. >> >> Hi Gregory. >> >> Kirkwood has the ability to put the DDR into self refresh mode, which >> is used as part of the second level idle mode. Does 370/XP have this? > > Indeed there is a self refresh bit on a DDR related register. I thought > this kind of feature is more likely used for suspend to ram. > > We plan to also submit the suspend to ram but not immediately. > >> >> For XP, with it being SMP, it would be a bit more complex, since you >> would not want to use it unless all CPUs were idle. > > I wonder how the others SMP ARM SoCs deal with it, I hope this time > there will be a framework available and we won't have to create it! ;) You shouldn't have to invent anything here. For low-power states that require all CPUs to be idle, we have "coupled" CPUidle states (c.f. drivers/cpuidle/coupled.) OMAP and Tegra are using this, but I believe Daniel wants to move away from this, so I'll let him elaborate. Kevin From mboxrd@z Thu Jan 1 00:00:00 1970 From: khilman@linaro.org (Kevin Hilman) Date: Fri, 13 Sep 2013 07:48:05 -0700 Subject: [PATCH v2 00/12] CPU idle for Armada XP In-Reply-To: <5232F43D.4040404@free-electrons.com> (Gregory CLEMENT's message of "Fri, 13 Sep 2013 13:17:17 +0200") References: <1379066801-16276-1-git-send-email-gregory.clement@free-electrons.com> <20130913110043.GJ19363@lunn.ch> <5232F43D.4040404@free-electrons.com> Message-ID: <871u4shj6i.fsf@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Gregory CLEMENT writes: > On 13/09/2013 13:00, Andrew Lunn wrote: >> >> On Fri, Sep 13, 2013 at 12:06:29PM +0200, Gregory CLEMENT wrote: >>> Hello, >>> >>> This patch set adds the CPU idle support for Armada XP and prepares >>> the support for Armada 370. This was based on the work of Nadav >>> Haklai. >> >> Hi Gregory. >> >> Kirkwood has the ability to put the DDR into self refresh mode, which >> is used as part of the second level idle mode. Does 370/XP have this? > > Indeed there is a self refresh bit on a DDR related register. I thought > this kind of feature is more likely used for suspend to ram. > > We plan to also submit the suspend to ram but not immediately. > >> >> For XP, with it being SMP, it would be a bit more complex, since you >> would not want to use it unless all CPUs were idle. > > I wonder how the others SMP ARM SoCs deal with it, I hope this time > there will be a framework available and we won't have to create it! ;) You shouldn't have to invent anything here. For low-power states that require all CPUs to be idle, we have "coupled" CPUidle states (c.f. drivers/cpuidle/coupled.) OMAP and Tegra are using this, but I believe Daniel wants to move away from this, so I'll let him elaborate. Kevin