From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751622AbaG2Siw (ORCPT ); Tue, 29 Jul 2014 14:38:52 -0400 Received: from mail.kmu-office.ch ([178.209.48.102]:54745 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750862AbaG2Siv (ORCPT ); Tue, 29 Jul 2014 14:38:51 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset= Content-Transfer-Encoding: 7bit Date: Tue, 29 Jul 2014 20:39:20 +0200 From: Stefan Agner To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, shawn.guo@freescale.com, kernel@pengutronix.de, peter.chen@freescale.com, linux-kernel@vger.kernel.org, jingchang.lu@freescale.com Subject: Re: [PATCH] ARM: imx: clk-vf610: introduce =?UTF-8?Q?clks=5Finit?= =?UTF-8?Q?=5Fon?= In-Reply-To: <2815679.ZycfkLhBgI@wuerfel> References: <1406643628-4061-1-git-send-email-stefan@agner.ch> <2815679.ZycfkLhBgI@wuerfel> Message-ID: <2a672a5d28af5425e1c406b0607befd5@agner.ch> User-Agent: Roundcube Webmail/1.0.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 2014-07-29 16:44, schrieb Arnd Bergmann: > On Tuesday 29 July 2014 16:20:28 Stefan Agner wrote: >> At the end of the boot process, the clock framework might disable >> required main PLL's. So far, this was no issue since drivers >> requested clocks, which are descended of the main PLL's (e.g. >> pll1_pfd1, which provides the system clock). >> >> To archive the full 500MHz system clock, DDR clock need to be a >> descendant of PLL2 rather than PLL1 (DDRC_CLK_SEL set to 0). The >> bootloader sets up the clocks accordingly before making use of >> DDR at all. However, in Linux, there is no driver using PLL2, >> which lead to PLL2 being disabled by the clock framework. >> >> With this patch, we make sure that the main system clock and the >> DDR clock are initially enabled and are kept enabled. >> >> Signed-off-by: Stefan Agner >> > > Wouldn't it be better to list this in the DT as a default for > the respective clocks? > What do you mean by that exactly? Creating a driver for the main PLL's and add device tree entries to instantiate them, along with a property like "boot-enabled" or similar? The approach chosen in this patch is aligned the way it's done for i.MX6 (see arch/arm/mach-imx/clk-imx6q.c). The whole clock module(s) in Vybrid are slightly striped variants found in i.MX6. For now, I would prefer to leave it that way. -- Stefan