From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932747AbbJNPgw (ORCPT ); Wed, 14 Oct 2015 11:36:52 -0400 Received: from mail-gw2-out.broadcom.com ([216.31.210.63]:15795 "EHLO mail-gw2-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932351AbbJNPgv (ORCPT ); Wed, 14 Oct 2015 11:36:51 -0400 X-IronPort-AV: E=Sophos;i="5.17,681,1437462000"; d="scan'208";a="77628569" Date: Wed, 14 Oct 2015 11:36:22 -0400 From: Jon Mason To: Ray Jui CC: Hauke Mehrtens , Florian Fainelli , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , "Russell King" , , , , , =?utf-8?B?UmFmYcWCIE1pxYJlY2tp?= Subject: Re: [PATCH 1/2] ARM: dts: bcm5301x: Add BCM SVK DT files Message-ID: <20151014153621.GD15160@broadcom.com> References: <1443824564-17291-1-git-send-email-jonmason@broadcom.com> <56192304.1050500@hauke-m.de> <20151013213818.GM12512@broadcom.com> <561D8908.2060803@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <561D8908.2060803@broadcom.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 13, 2015 at 03:43:20PM -0700, Ray Jui wrote: > > > On 10/13/2015 2:38 PM, Jon Mason wrote: > > On Sat, Oct 10, 2015 at 04:39:00PM +0200, Hauke Mehrtens wrote: > >> On 10/03/2015 12:22 AM, Jon Mason wrote: > >>> Add device tree files for Broadcom Northstar based SVKs. Since the > >>> bcm5301x.dtsi already exists, all that is necessary is the dts files to > >>> enable the UARTs (and specify the RAM size for the 4708/9). With these > >>> files, the SVKs are able to boot to shell. > >>> > >>> Signed-off-by: Jon Mason > >>> --- > >>> arch/arm/boot/dts/Makefile | 5 +++- > >>> arch/arm/boot/dts/bcm94708.dts | 52 +++++++++++++++++++++++++++++++++++ > >>> arch/arm/boot/dts/bcm94709.dts | 52 +++++++++++++++++++++++++++++++++++ > >>> arch/arm/boot/dts/bcm953012k.dts | 59 ++++++++++++++++++++++++++++++++++++++++ > >>> 4 files changed, 167 insertions(+), 1 deletion(-) > >>> create mode 100644 arch/arm/boot/dts/bcm94708.dts > >>> create mode 100644 arch/arm/boot/dts/bcm94709.dts > >>> create mode 100644 arch/arm/boot/dts/bcm953012k.dts > >>> > > >>> +&uart0 { > >>> + clock-frequency = <62499840>; > >> > >> Just out of curiosity on what does this clock frequency depend? I saw > >> your patch adding a real clock driver which should make this obsolete. > > > > Better to add this now, as the device tree part might be out of sync > > for a time. > > Sure, this can potentially be a reason to not using the real clock node > and just use a hardcoded clock frequency for now, until the other clock > change is merged, then you can submit another patch to use it. > > Also, is it not better to make the UARTs a static clock > > and not dependent on the clk driver? > > > > I disagree. You should always use the real clock driver for querying the > clock frequency, in the case when the clock driver is available. > > Today one can change the core clock for UART in the bootloader for > various reasons (and we saw that happening a lot in the past), which in > this case will make your kernel not seeing any console output. > > By always querying the clock rate based on real registers instead of a > hardcoded value, you don't have that issue and your kernel is less > dependent on any changes in the bootloader. Fair enough. This is moot until the clk driver changes get pulled in. This file can be changed at that time :) Thanks, Jon > > > Thanks, > > Jon > >