Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752740AbZKQMqk (ORCPT ); Tue, 17 Nov 2009 07:46:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752313AbZKQMqk (ORCPT ); Tue, 17 Nov 2009 07:46:40 -0500 Received: from mail-yw0-f202.google.com ([209.85.211.202]:45603 "EHLO mail-yw0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751445AbZKQMqj convert rfc822-to-8bit (ORCPT ); Tue, 17 Nov 2009 07:46:39 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=sArVZb0YSck90fh9QWv7vOpTkztDyvjY3b7zSFBDVmWxjZEJJJyAU2Z0Y0aYU2lYNJ Kq2ZIcmv5xEcgZrdvACg5GxtBU8+J07Thc4JN+MgcRdEBCP+QZ8mvJJzETYy+ZlmKHQ0 +RLwd1lAGGO5BxhYCUjYo2gMs/my9XuTGK0Rw= MIME-Version: 1.0 In-Reply-To: <20091116153000.GB29479@sirena.org.uk> References: <20091109105858.GB1245@sirena.org.uk> <20091109133136.GC1245@sirena.org.uk> <20091116153000.GB29479@sirena.org.uk> Date: Tue, 17 Nov 2009 21:46:35 +0900 Message-ID: Subject: Re: Null suspend/resume functions From: Magnus Damm To: Mark Brown Cc: Kuninori Morimoto , alsa-devel@alsa-project.org, linux-pm@lists.linux-foundation.org, Magnus Damm , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2444 Lines: 54 Hi Mark, On Tue, Nov 17, 2009 at 12:30 AM, Mark Brown wrote: > On Mon, Nov 09, 2009 at 01:31:36PM +0000, Mark Brown wrote: >> On Mon, Nov 09, 2009 at 10:58:58AM +0000, Mark Brown wrote: >> > On Mon, Nov 09, 2009 at 11:54:47AM +0900, Kuninori Morimoto wrote: > > Any chance someone from the PM side could comment on the issue below? > >> > > +static int fsi_runtime_nop(struct device *dev) >> > > +{ >> > > + /* Runtime PM callback shared between ->runtime_suspend() >> > > + ?* and ->runtime_resume(). Simply returns success. >> > > + ?* >> > > + ?* This driver re-initializes all registers after >> > > + ?* pm_runtime_get_sync() anyway so there is no need >> > > + ?* to save and restore registers here. >> > > + ?*/ >> > > + return 0; >> > > +} >> > >> > This sets off alarm bells but it's perfectly reasonable, especially with >> > platforms able to put things into a low power state with no explicit >> > driver code now they can do power domain style things like SH. ?I've >> > CCed in the PM folks since this seems like a perfectly reasonable use >> > case which ought to be handled more nicely. On SuperH we have Runtime PM enabled on a few platforms together with a few updated drivers. The latest driver to become more power aware is this FSI driver. It's all quite simple, in the FSI driver we enable the clock to the FSI hardware using Runtime PM functions, and whenever the clock is turned off the SuperH specific bus code _may_ decide to call ->runtime_suspend() and turn off the power domain. The "_may_" comes from the fact that multiple hardware blocks may be grouped together into a single power domain, and all devices in the power domain must support Runtime PM and have their clocks disabled before we can turn off the power. At this point the SuperH specific platform bus code requires the callbacks ->runtime_suspend() and ->runtime_resume() to be present. It may be a good idea to allow them to be NULL in the future or maybe having some shared functions, but before starting to break out stuff I'd like to see how other Runtime PM implementations deal with this. So unless people object I prefer to keep it as-is for now. / magnus -- 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/