From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter De Schrijver Subject: Re: [PATCH V3 5/5] ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode Date: Tue, 18 Dec 2012 12:18:19 +0200 Message-ID: <20121218101819.GP19258@tbergstrom-lnx.Nvidia.com> References: <1355797861-12759-1-git-send-email-josephl@nvidia.com> <1355797861-12759-6-git-send-email-josephl@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <1355797861-12759-6-git-send-email-josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Joseph Lo Cc: Stephen Warren , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , Colin Cross List-Id: linux-tegra@vger.kernel.org On Tue, Dec 18, 2012 at 03:31:01AM +0100, Joseph Lo wrote: > The "powered-down" cpuidle mode of Tegra20 needs the CPU0 be the last one > core to go into this mode before other core. The coupled cpuidle framework > can help to sync the MPCore to coupled state then go into "powered-down" > idle mode together. The driver can just assume the MPCore come into > "powered-down" mode at the same time. No need to take care if the CPU_0 > goes into this mode along and only can put it into safe idle mode (WFI). > > The powered-down state of Tegra20 requires power gating both CPU cores. > When the secondary CPU requests to enter powered-down state, it saves > its own contexts and then enters WFI for waiting CPU0 in the same state. > When the CPU0 requests powered-down state, it attempts to put the secondary > CPU into reset to prevent it from waking up. Then power down both CPUs > together and power off the cpu rail. > > Be aware of that, you may see the legacy power state "LP2" in the code > which is exactly the same meaning of "CPU power down". > > Based on the work by: > Colin Cross > Gary King > > Signed-off-by: Joseph Lo > --- > V3: > * sqash last two patch in previous version to support coupled cpuidle > directly nitpick - it should be 'squash'. Cheers, Peter.