From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lina Iyer Subject: Re: [PATCH v4 7/8] qcom: cpuidle: Add cpuidle driver for QCOM cpus Date: Wed, 27 Aug 2014 14:35:13 -0600 Message-ID: <20140827203513.GC79706@ilina-mac.domain> References: <1408486537-6358-1-git-send-email-lina.iyer@linaro.org> <1408486537-6358-8-git-send-email-lina.iyer@linaro.org> <53F54A5C.3060002@linaro.org> <20140821143643.GA60920@ilina-mac.local> <7hvbpdet5d.fsf@paris.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Return-path: Received: from mail-pa0-f50.google.com ([209.85.220.50]:44030 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750929AbaH0UfX (ORCPT ); Wed, 27 Aug 2014 16:35:23 -0400 Received: by mail-pa0-f50.google.com with SMTP id et14so1215065pad.23 for ; Wed, 27 Aug 2014 13:35:21 -0700 (PDT) Content-Disposition: inline In-Reply-To: <7hvbpdet5d.fsf@paris.lan> Sender: linux-arm-msm-owner@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org To: Kevin Hilman Cc: Daniel Lezcano , sboyd@codeaurora.org, davidb@codeaurora.org, galak@codeaurora.org, linux-arm-msm@vger.kernel.org, lorenzo.pieralisi@arm.com, msivasub@codeaurora.org On Wed, Aug 27, 2014 at 10:31:26AM -0700, Kevin Hilman wrote: >Lina Iyer writes: > >> On Thu, Aug 21, 2014 at 03:24:44AM +0200, Daniel Lezcano wrote: >>>On 08/20/2014 12:15 AM, Lina Iyer wrote: > >[...] > >>> >>> So IIUC, if you specify the index 1, that means the state[0] will be >>> the default WFI. But you override the callback below in the loop. >>> >>> I recommend you use the default arm wfi callback but you implement >>> the cpu_do_idle for your platform. >> >> Yes, it was intended. I dont want to define two WFI states. The >> architectural WFI does not buy us enough compared to WFI that SoC can >> do. L2 can go into low power modes when the core is in WFI and for that >> I would like to have all WFI's enter SoC framework. > >If the L2 is going into low-power, that means there will be higher >latency coming out compared to the architectural WFI, correct? > Thats right. Architecturally L2 deeper sleep modes (which include L2 logic off) may reset the core. So L2 deeper sleep modes with cores in WFI is not a suggested possibility. >If you have both, and the latency/residency numbers are accurate, the >governor is then left to pick the right one. So, what's wrong with >having both? I agree, but there is very little benefit to doing architectural WFI vs platform WFI in most cases. The residencies are too close and almost the same, doesnt warrant a separate functions for that. There is no thing wrong, just dint see a lot of benefit, thats all. What do you think? > >Kevin >