Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751585AbbFXHya (ORCPT ); Wed, 24 Jun 2015 03:54:30 -0400 Received: from mailgw02.mediatek.com ([210.61.82.184]:58898 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750947AbbFXHyU (ORCPT ); Wed, 24 Jun 2015 03:54:20 -0400 X-Listener-Flag: 11101 Message-ID: <1435132455.28866.21.camel@mtksdaap41> Subject: Re: [PATCH] arm64: dts: mt8173: add clock_null From: James Liao To: Heiko =?ISO-8859-1?Q?St=FCbner?= CC: , Eddie Huang , Matthias Brugger , , Sascha Hauer , , , Date: Wed, 24 Jun 2015 15:54:15 +0800 In-Reply-To: <8860488.JuX1EN5tWB@diego> References: <1434605351-64592-1-git-send-email-eddie.huang@mediatek.com> <8371528.SNAmOgosfF@phil> <1434944317.25948.8.camel@mtksdaap41> <8860488.JuX1EN5tWB@diego> Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2118 Lines: 53 Hi Heiko, On Mon, 2015-06-22 at 14:53 +0200, Heiko St?bner wrote: > Hi James, > > Am Montag, 22. Juni 2015, 11:38:37 schrieb James Liao: > > On Fri, 2015-06-19 at 13:36 +0200, Heiko Stuebner wrote: > > > > Some clocks such as clkph_mck_o, we don't really care where they come > > from and what frequencies are. We model these clocks just because they > > or their derived clocks can be the source of topckgen muxes. Is there a > > better way to model "don't care" clocks? > > There are two different concepts at work here. You might not care in your > kernel driver implementation _at the moment_ where the clocks come from; but > the devicetree is supposed to model how the hardware is structured and not > contain implementation specific details. If we model "don't care" clocks inside the driver (i.e. create clk_null in clock driver), then we don't need to model the dummy clock in device. Is it an acceptable way? > So the clock tree should be modeled according to how the hardware is layed out > not how you want to use the clocks at the moment :-) . > > It would it any case be good, if you could describe where these clocks come > from in the hardware, so we can find the best solution on how to model those. In fact, I don't know where these clocks come from at all, especially when they come from outside of SoC. Besides, some clocks don't need to model in CCF, but they can be the source of clocks that controlled by CCF. I don't think ALL clocks on a SoC need to be handled in CCF, so there should be some clocks don't have a "real" or "correct" parent. In current implementation I use a dummy clock (clk_null) to be the unreal parent. Do you think we should model as more clocks as we can in CCF even we don't need them? If no, how do we handle those clocks which are not handled in CCF but can be parent of CCF clocks? Best regards, James -- 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/