Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752817Ab0LLMSd (ORCPT ); Sun, 12 Dec 2010 07:18:33 -0500 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:34935 "EHLO opensource2.wolfsonmicro.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752489Ab0LLMSb (ORCPT ); Sun, 12 Dec 2010 07:18:31 -0500 Date: Sun, 12 Dec 2010 12:18:42 +0000 From: Mark Brown To: Saravana Kannan Cc: Liam Girdwood , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] regulator: Call into regulator driver only when voltage min/max really changes. Message-ID: <20101212121842.GC15189@opensource.wolfsonmicro.com> References: <1292151342-12970-1-git-send-email-skannan@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1292151342-12970-1-git-send-email-skannan@codeaurora.org> X-Cookie: Your present plans will be successful. User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1347 Lines: 26 On Sun, Dec 12, 2010 at 02:55:40AM -0800, Saravana Kannan wrote: > Even in cases where the consumer driver calls the regulator core with > different voltage min/max values, the application of the various > voltage constraints could result in the min/max voltage values passed > to the regulator driver to be unchanged since the previous invocation. Out of interest do we have any examples of consumers that do this sufficiently often and/or in paths sufficiently performance critical for it to be an issue? Sounds like there might be room for optimisation in those consumers. > Optimize these cases by not calling into the regulator driver and not > sending incorrect/unnecessary voltage change notifications. Acked-by: Mark Brown The down side of doing this is that if the regulator state changes underneath us we've now got no way of recovering from that situation. This is something that's only partially supported by the API at the minute but it's nice to have a story about how drivers can work with this. I'll send a patch adding an explicit sync API. -- 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/