Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751950Ab1BSHZg (ORCPT ); Sat, 19 Feb 2011 02:25:36 -0500 Received: from mail-bw0-f46.google.com ([209.85.214.46]:47466 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751368Ab1BSHZd convert rfc822-to-8bit (ORCPT ); Sat, 19 Feb 2011 02:25:33 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type :content-transfer-encoding; b=T8pwQ8b7Xva3Z347Rxd3rDwpxTxfWQuwHMsHfIysdaNawaB/4Enr5dyDjucWsBQsB1 nk6PO4aQ5zaEHDwCIL4NYVTUjzkQfR8dhbdvc6P71Ht0BAYxcTYj/dGP2+CpKg+oKUWi 6D5bvUIrV4DFYEJekg32i5ZQjebAcdE6zT6U8= MIME-Version: 1.0 In-Reply-To: <20110218202744.GA19427@n2100.arm.linux.org.uk> References: <201102181928.05911.rjw@sisk.pl> <201102182120.29977.rjw@sisk.pl> <20110218202744.GA19427@n2100.arm.linux.org.uk> From: Rabin Vincent Date: Sat, 19 Feb 2011 12:54:52 +0530 X-Google-Sender-Auth: AkyY7dgy0q5zrozlB5a__4AyHwQ Message-ID: Subject: Re: platform/i2c busses: pm runtime and system sleep To: Russell King - ARM Linux Cc: "Rafael J. Wysocki" , khilman@ti.com, magnus.damm@gmail.com, LKML , stern@rowland.harvard.edu, linux-i2c@vger.kernel.org, linux-pm@lists.linux-foundation.org, linux-arm-kernel , Linus Walleij 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: 1745 Lines: 34 On Sat, Feb 19, 2011 at 01:57, Russell King - ARM Linux wrote: > Do we have any pressing need to convert AMBA stuff? ?I haven't heard any > reason yet to convert them to runtime PM - they don't even make any > runtime PM calls. > > Maybe Linus can comment on the PM stuff as he has SoCs with these in. > As my boards don't have any sensible PM support, I don't have any > visibility of what PM facilities would be required. The rationale for runtime power control is the same as that for 65500fa94aaeb3 "ARM: 6467/1: amba: optional PrimeCell core voltage switch". As compared to the regulator API which that patch is using, the runtime pm usage is more flexible (for example allowing certain power control APIs to be called from atomic context), provides callbacks for asynchronous turnoff with callbacks back to the driver to save/restore state (runtime_suspend()/runtime_resume()), and provides core support for things like "autosuspend" which allows delaying suspend until some time after last inactivity. Using runtime PM also allows use of the new device-level power domain support ("PM: Add support for device power domains", in -next) to easily implement SoC-specific handling. We need to first add bus support for this to allow drivers to use this API. It is possible to make the AMBA patch smaller and touch only the AMBA bus code by implementing support for the legacy bus-specific suspend/resume calls, and drivers can be later converted to pm-ops as needed. -- 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/