Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753594AbbGAGt6 (ORCPT ); Wed, 1 Jul 2015 02:49:58 -0400 Received: from metis.ext.pengutronix.de ([92.198.50.35]:35492 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752797AbbGAGtq (ORCPT ); Wed, 1 Jul 2015 02:49:46 -0400 Date: Wed, 1 Jul 2015 08:49:35 +0200 From: Sascha Hauer To: James Liao Cc: Heiko =?iso-8859-15?Q?St=FCbner?= , linux-mediatek@lists.infradead.org, Eddie Huang , Matthias Brugger , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, djkurtz@chromium.org, Mike Turquette , Stephen Boyd , ted.lin@mediatek.com Subject: Re: [PATCH] arm64: dts: mt8173: add clock_null Message-ID: <20150701064935.GC18611@pengutronix.de> References: <1434605351-64592-1-git-send-email-eddie.huang@mediatek.com> <8860488.JuX1EN5tWB@diego> <1435132455.28866.21.camel@mtksdaap41> <1510058.fTE6dlSRsH@diego> <1435655229.19330.15.camel@mtksdaap41> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1435655229.19330.15.camel@mtksdaap41> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 08:26:01 up 6 days, 47 min, 63 users, load average: 0.25, 0.14, 0.14 User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1620 Lines: 42 On Tue, Jun 30, 2015 at 05:07:09PM +0800, James Liao wrote: > Hi Heiko, > > There are 4 clocks which are derived from clk_null directly in current > topckgen implementation: > > clkph_mck_o, dpi_ck, usb_syspll_125m, hdmitx_dig_cts > > Our designer mentioned 2 things about external clocks: > > 1. These 4 clocks come from analog macro, not from PLL, nor from > external clocks directly. Ok, this means there actually are clocks. We can't control these clock and they have some known or unknown rate. This makes them fixed clocks. Just specify them in the device tree and you are done. Give them reasonable names and the rate if you know it, 0 otherwise. The problem is not that you use fixed clocks for non software controllable clocks of unknwown rates, but that you try to use a single clock for all of them and name it 'dummy' or 'null'. Name it dpi_ck { compatible = "fixed-clock"; rate = <0>; /* unknown, generated by some Analog block */ }; Technically it's the same, but it sounds much more professional and like you know what you are doing ;) Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- 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/