From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [PATCH 1/2] ARM: s3c64xx: cpuidle: convert to platform driver Date: Wed, 30 Oct 2013 15:50:24 -0700 Message-ID: <52718D30.8010509@linaro.org> References: <1382685074-16502-1-git-send-email-daniel.lezcano@linaro.org> <526AEF6B.2000404@linaro.org> <52717D97.8090905@linaro.org> <1807659.lxGmRkUGnf@flatron> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-oa0-f53.google.com ([209.85.219.53]:56539 "EHLO mail-oa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751848Ab3J3Wu0 (ORCPT ); Wed, 30 Oct 2013 18:50:26 -0400 Received: by mail-oa0-f53.google.com with SMTP id n12so2193415oag.26 for ; Wed, 30 Oct 2013 15:50:26 -0700 (PDT) In-Reply-To: <1807659.lxGmRkUGnf@flatron> Sender: linux-samsung-soc-owner@vger.kernel.org List-Id: linux-samsung-soc@vger.kernel.org To: Tomasz Figa Cc: ben-linux@fluff.org, kgene.kim@samsung.com, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org On 10/30/2013 03:40 PM, Tomasz Figa wrote: > Hi Daniel, > > On Wednesday 30 of October 2013 14:43:51 Daniel Lezcano wrote: >> On 10/25/2013 03:23 PM, Daniel Lezcano wrote: >> >> [ ... ] >> >>>>> Won't it be worth to add a new WFI_SLEEP state to the cpuidle dri= ver >>>>> ? >>>> >>>> I don't think so. How a suspend-to-RAM specific thing like WFI_SLE= EP >>>> could >>>> be relevant to a cpuidle driver? (Unless there are some plans to >>>> consolidate STR with cpuidle that I haven't heard about...) >>> >>> I finally found a documentation for the s3c6410x and the descriptio= n >>> of >>> the different modes. Indeed, the sleep mode is not adequate for a >>> cpuidle state. What about the 'stop' and 'deep stop' state ? >> >> Hi Thomas, >> >> just a reminder about the question above, so I can go ahead: fix wha= t >> you pointed out or remove the driver directly. >> >> You mentionned in the previous email the STOP is not usful because i= t >> can be controlled by manually outside of the cpuidle driver. But I s= ee >> in the documentation, the stop states power gates the cpu and deep-s= top >> stops the regulator. > > STOP clock-gates the CPU and DEEP-STOP power-gates it by stopping the > regulator. > > There are some interesting aspects of those modes, like memory self- > refresh, PLL power-off and system-wide down clocking, but I believe t= hey > are too tricky to handle (coupling with device PM, stopped timers) an= d > with too little possible power saving to justify the effort of adding > support for them. > > In the end, I haven't seen support for them implemented even in stran= ge > vendor kernels used even on production devices, like Android phones. > >> >> If these states have to been added later, still it worth to remove t= he >> driver ? > > I don't think that anybody is even going to add support for them and = by > anybody I should probably mean myself, since I'm currently the only p= erson > actively adding new code for this platform, as a part of my hobby. Ok, I will kill the driver then. Thanks -- Daniel --=20 Linaro.org =E2=94=82 Open source software fo= r ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniel.lezcano@linaro.org (Daniel Lezcano) Date: Wed, 30 Oct 2013 15:50:24 -0700 Subject: [PATCH 1/2] ARM: s3c64xx: cpuidle: convert to platform driver In-Reply-To: <1807659.lxGmRkUGnf@flatron> References: <1382685074-16502-1-git-send-email-daniel.lezcano@linaro.org> <526AEF6B.2000404@linaro.org> <52717D97.8090905@linaro.org> <1807659.lxGmRkUGnf@flatron> Message-ID: <52718D30.8010509@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 10/30/2013 03:40 PM, Tomasz Figa wrote: > Hi Daniel, > > On Wednesday 30 of October 2013 14:43:51 Daniel Lezcano wrote: >> On 10/25/2013 03:23 PM, Daniel Lezcano wrote: >> >> [ ... ] >> >>>>> Won't it be worth to add a new WFI_SLEEP state to the cpuidle driver >>>>> ? >>>> >>>> I don't think so. How a suspend-to-RAM specific thing like WFI_SLEEP >>>> could >>>> be relevant to a cpuidle driver? (Unless there are some plans to >>>> consolidate STR with cpuidle that I haven't heard about...) >>> >>> I finally found a documentation for the s3c6410x and the description >>> of >>> the different modes. Indeed, the sleep mode is not adequate for a >>> cpuidle state. What about the 'stop' and 'deep stop' state ? >> >> Hi Thomas, >> >> just a reminder about the question above, so I can go ahead: fix what >> you pointed out or remove the driver directly. >> >> You mentionned in the previous email the STOP is not usful because it >> can be controlled by manually outside of the cpuidle driver. But I see >> in the documentation, the stop states power gates the cpu and deep-stop >> stops the regulator. > > STOP clock-gates the CPU and DEEP-STOP power-gates it by stopping the > regulator. > > There are some interesting aspects of those modes, like memory self- > refresh, PLL power-off and system-wide down clocking, but I believe they > are too tricky to handle (coupling with device PM, stopped timers) and > with too little possible power saving to justify the effort of adding > support for them. > > In the end, I haven't seen support for them implemented even in strange > vendor kernels used even on production devices, like Android phones. > >> >> If these states have to been added later, still it worth to remove the >> driver ? > > I don't think that anybody is even going to add support for them and by > anybody I should probably mean myself, since I'm currently the only person > actively adding new code for this platform, as a part of my hobby. Ok, I will kill the driver then. Thanks -- Daniel -- Linaro.org ? Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog