Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757946Ab0GNWvz (ORCPT ); Wed, 14 Jul 2010 18:51:55 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:57049 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756571Ab0GNWvx convert rfc822-to-8bit (ORCPT ); Wed, 14 Jul 2010 18:51:53 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=vvenhb+X/gqzkLCxX95BROoK0yXYHaV5kyFsOFLC1jRxitUKpAyI95Y7711GnMDiYk W1NIE22V1UPtkkN/4IuMM1KpSh+LWt2fsCdQl+PcsZUigm/aOpZPG3sUOSm1YTGjAkJU ohD92MLWRtU6VO6r0iBGJR66p17riLErPpIbs= MIME-Version: 1.0 In-Reply-To: <20100714184251.GG5933@sirena.org.uk> References: <20100713203852.GA1756@rakim.wolfsonmicro.main> <20100714145053.GA1689@bnru01.bnr.st.com> <20100714145748.GF31073@rakim.wolfsonmicro.main> <20100714153643.GB1689@bnru01.bnr.st.com> <20100714154726.GH31073@rakim.wolfsonmicro.main> <20100714160941.GC1689@bnru01.bnr.st.com> <20100714162048.GA27512@rakim.wolfsonmicro.main> <20100714164708.GD1689@bnru01.bnr.st.com> <20100714170323.GF5933@sirena.org.uk> <20100714173650.GA21893@bnru01.bnr.st.com> <20100714184251.GG5933@sirena.org.uk> Date: Thu, 15 Jul 2010 00:51:50 +0200 X-Google-Sender-Auth: RJ-xZMHHimariSaGw_Xbq7V2SD8 Message-ID: Subject: Re: [PATCH v2 2/2] ux500: add ab8500-regulators machine specific data From: Linus Walleij To: Mark Brown Cc: Sundar R IYER , Bengt JONSSON , "linux-kernel@vger.kernel.org" , STEricsson_nomadik_linux , "lrg@slimlogic.co.uk" , "linux-arm-kernel@lists.infradead.org" , "sameo@linux.intel.com" 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: 1453 Lines: 31 2010/7/14 Mark Brown : >> > This is normal, but for fairly obvious reasons the very lowest power >> > states are generally handled outside of the regulator API at a hardware >> > level via hardware signals to the regulator. ?It's not normally part of >> > the runtime constraints for use while the CPU is live. > >> Yes. But my point was that even at a lower level than kernel (BIOS/firmware?) >> the switching would happen via SW. Please correct me if I am wrong! > > Well, ultimately it's always triggered by software but the actual signal > to the regulator is often a logic level output by the SoC as the > processor enters a low power state rather than an I2C/SPI write. I can answer this: on the U300 we had such autonomous signals that would augment the power state of the regulators by special sleep signals. For U8500 there is a dedicated autonomous system in the silicon, called PRCMU (Power Reset Clock Management Unit) that will actually do this using I2C because it has its own CPU and can transmit I2C messages even when the ARM CPU cores are turned off. So this is indeed a first-timer and not strange that it looks unfamiliar ... Yours, Linus Walleij -- 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/