Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934323Ab0HFBXE (ORCPT ); Thu, 5 Aug 2010 21:23:04 -0400 Received: from smtp-out.google.com ([216.239.44.51]:39568 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934131Ab0HFBW7 convert rfc822-to-8bit (ORCPT ); Thu, 5 Aug 2010 21:22:59 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:content-transfer-encoding:x-system-of-record; b=SRCXBIHncoSKPQGDKQo6msn0AbMBBoE3K0MN4VvyCQMNXtYpMpP+agko4J94szxDU RMxTFOQS7fBx/m3+WFOcg== MIME-Version: 1.0 In-Reply-To: References: <20100805004802.GP24163@linux.vnet.ibm.com> <20100805151211.GA10080@linux.vnet.ibm.com> <20100805203102.GN2447@linux.vnet.ibm.com> <20100805230304.GQ2447@linux.vnet.ibm.com> Date: Thu, 5 Aug 2010 18:22:56 -0700 Message-ID: Subject: Re: Attempted summary of suspend-blockers LKML thread From: Brian Swetland To: david@lang.hm Cc: paulmck@linux.vnet.ibm.com, kevin granade , =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= , Matthew Garrett , "Rafael J. Wysocki" , Arjan van de Ven , linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, pavel@ucw.cz, florian@mickler.org, stern@rowland.harvard.edu, peterz@infradead.org, tglx@linutronix.de, alan@lxorguk.ukuu.org.uk Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1855 Lines: 39 On Thu, Aug 5, 2010 at 6:01 PM, wrote: > On Thu, 5 Aug 2010, Brian Swetland wrote: >> On Thu, Aug 5, 2010 at 5:16 PM,   wrote: >>>>> >>>>> So for an mp3 playback, does an Android suspend between data fetches? >>>> >>>> It can if the latency is long enough (which is why I point out low >>>> power audio which is usually high latency).  For low latency (system >>>> sounds, etc) 10-25ms between buffers it's not practical to fully >>>> suspend but we will go to the lowest power state in idle if possible. >>> >>> the playback is able to continue even with all the clocks stopped? that >>> surprises me. I would hav expected it to be able to sleep while playing >>> audio, but not do a full suspend. >> >> Obviously not all clocks are stopped (the DSP and codec are powered >> and clocked, for example), but yeah we can clock gate and power gate >> the cpu and most other peripherals while audio is playing on a number >> of ARM SoC designs available today (and the past few years). > > does this then mean that you have multiple variations of suspend? > > for example, one where the audio stuff is left powered, and one where it > isn't? While the cpu (and the bulk of the system) is suspended, it's not uncommon for some peripherals to continue to operate -- for example a cellular radio, gps, low power audio playback, etc. Details will vary depending on the SoC and board design. It's not so much a different suspend mode (the system is still suspended), just a matter of whether a peripheral can operate independently (and if it is lower power for it to do so). Brian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/