From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753400Ab0IQLpu (ORCPT ); Fri, 17 Sep 2010 07:45:50 -0400 Received: from mailout2.samsung.com ([203.254.224.25]:40651 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751801Ab0IQLps (ORCPT ); Fri, 17 Sep 2010 07:45:48 -0400 Date: Fri, 17 Sep 2010 13:45:36 +0200 From: Marek Szyprowski Subject: RE: [PATCH] regulator: Add support samsung power domain In-reply-to: <20100917113050.GA4322@rakim.wolfsonmicro.main> To: "'Mark Brown'" , "'Kukjin Kim'" Cc: "'Jeongbae Seo'" , linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, "'Changhwan Youn'" , linux-arm-kernel@lists.infradead.org, lrg@slimlogic.co.uk Message-id: <007b01cb565d$db4376d0$91ca6470$%szyprowski@samsung.com> MIME-version: 1.0 X-Mailer: Microsoft Office Outlook 12.0 Content-type: text/plain; charset=us-ascii Content-language: pl Content-transfer-encoding: 7BIT Thread-index: ActWXIsMcgX2GYaaTAmJ//vvnGVswQAAIQYw References: <1284717532-9992-1-git-send-email-kgene.kim@samsung.com> <20100917113050.GA4322@rakim.wolfsonmicro.main> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Friday, September 17, 2010 1:31 PM Mark Brown wrote: > Another option to consider here is using runtime PM - other platforms > seem to be going down that route, and are using it to also factor clock > management for the IP blocks out (so that the block's clocks get enabled > and disabled automatically when the block is active without needing any > code in the driver). The approach with merging power domains with clocks have some disadvantages. In some cases the clock gating and power gating should be distinguished. Just assume an IP like a video codec. It has it's own internal state machine. It gets reset when the ip is power gated, but it is preserved during clock gating. The driver might want to do a clock gating when it is waiting for a new frame to decode, but should do power gating only when the device has been closed. Having a set of fake clocks just for power gating imho doesn't look good. Best regards -- Marek Szyprowski Samsung Poland R&D Center