From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752427AbbJMWnY (ORCPT ); Tue, 13 Oct 2015 18:43:24 -0400 Received: from mail-gw2-out.broadcom.com ([216.31.210.63]:6529 "EHLO mail-gw2-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751188AbbJMWnX (ORCPT ); Tue, 13 Oct 2015 18:43:23 -0400 X-IronPort-AV: E=Sophos;i="5.17,680,1437462000"; d="scan'208";a="77557757" Subject: Re: [PATCH 1/2] ARM: dts: bcm5301x: Add BCM SVK DT files To: Jon Mason , Hauke Mehrtens References: <1443824564-17291-1-git-send-email-jonmason@broadcom.com> <56192304.1050500@hauke-m.de> <20151013213818.GM12512@broadcom.com> CC: Florian Fainelli , Rob Herring , Pawel Moll , Mark Rutland , "Ian Campbell" , Kumar Gala , Russell King , , , , , =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= From: Ray Jui Message-ID: <561D8908.2060803@broadcom.com> Date: Tue, 13 Oct 2015 15:43:20 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151013213818.GM12512@broadcom.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > Thanks, > Jon >