From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH] video: omap2: dss: RET on idle, enable/disable dss clocks only when needed. Date: Tue, 22 Sep 2009 07:54:20 -0700 Message-ID: <877hvrf2sj.fsf@deeprootsystems.com> References: <1253230586-931-1-git-send-email-mike@android.com> <1253262472.28956.10.camel@tubuntu> <8bb80c380909181033s2fd5e3a1o16404f1667760b25@mail.gmail.com> <1253514408.4690.5.camel@tubuntu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-qy0-f173.google.com ([209.85.221.173]:58267 "EHLO mail-qy0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752435AbZIVOyV (ORCPT ); Tue, 22 Sep 2009 10:54:21 -0400 Received: by qyk3 with SMTP id 3so2863831qyk.4 for ; Tue, 22 Sep 2009 07:54:25 -0700 (PDT) In-Reply-To: <1253514408.4690.5.camel@tubuntu> (Tomi Valkeinen's message of "Mon\, 21 Sep 2009 09\:26\:48 +0300") Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: tomi.valkeinen@nokia.com Cc: ext Mike Chan , "linux-omap@vger.kernel.org" Tomi Valkeinen writes: > Hi, > > On Fri, 2009-09-18 at 19:33 +0200, ext Mike Chan wrote: >> On Fri, Sep 18, 2009 at 1:27 AM, Tomi Valkeinen >> wrote: >> > Hi, >> > >> > If you disable the clocks to allow RET, you also allow OFF mode. And >> > resuming from OFF mode hasn't been implemented for DSI, if I recall >> > right. And when I was testing it, it didn't seem to be trivial with the >> > DSI PLL. >> > >> >> You can limiting the pwrdm next state to RET when being called from cpuidle. > > No, you _must_ limit it to RET. Otherwise the DSI will break down. So we > can either keep the dsi code as it is now, or explicitely disable OFF > mode and then apply your patch. But your patch alone won't work. Or could add a hack to this patch so that 'enable_off_mode' doesn't affect DSS_MOD until DSS has off-mode support. > In the long run I think we anyway need to somehow dynamically manage the > power state. I haven't measured it but I believe resuming from OFF will > have a bit of a penalty, as (I think) DSI PLL etc. will have to > reinitialized. But it would still be good to allow RET whenever > possible, and OFF only after some period of inactivity. This is the purpose of latency constraints. These can be used when the latency of going OFF will cause a problem. Kevin