From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0016C2D0DB for ; Fri, 31 Jan 2020 15:33:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 955CF20707 for ; Fri, 31 Jan 2020 15:33:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728922AbgAaPdQ (ORCPT ); Fri, 31 Jan 2020 10:33:16 -0500 Received: from bmailout1.hostsharing.net ([83.223.95.100]:44233 "EHLO bmailout1.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728860AbgAaPdQ (ORCPT ); Fri, 31 Jan 2020 10:33:16 -0500 X-Greylist: delayed 540 seconds by postgrey-1.27 at vger.kernel.org; Fri, 31 Jan 2020 10:33:15 EST Received: from h08.hostsharing.net (h08.hostsharing.net [83.223.95.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.hostsharing.net", Issuer "COMODO RSA Domain Validation Secure Server CA" (not verified)) by bmailout1.hostsharing.net (Postfix) with ESMTPS id 7222330008C8C; Fri, 31 Jan 2020 16:24:14 +0100 (CET) Received: by h08.hostsharing.net (Postfix, from userid 100393) id 2E8DC22B001; Fri, 31 Jan 2020 16:24:14 +0100 (CET) Date: Fri, 31 Jan 2020 16:24:14 +0100 From: Lukas Wunner To: Nicolas Saenz Julienne Cc: Matthias Brugger , matthias.bgg@kernel.org, linux-arm-kernel@lists.infradead.org, Matthias Brugger , Scott Branden , gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Ray Jui , Stephen Boyd , Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, linux-rpi-kernel@lists.infradead.org, linux-serial@vger.kernel.org, jslaby@suse.com Subject: Re: [PATCH] serial: 8250_early: Add earlycon for BCM2835 aux uart Message-ID: <20200131152414.73tgwsfhzgu4apkx@wunner.de> References: <20200128141958.vwbxoqglt5gw4xj5@wunner.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Thu, Jan 30, 2020 at 05:11:55PM +0100, Nicolas Saenz Julienne wrote: > BTW did you had the oportunity to have a go at the patch? I've just performed a quick test and it doesn't work for me. If I add stdout-path = "serial1:115200n8"; to the chosen node, I only get a regular console with this patch, not an earlycon. > > The problem is that in mainline, bcm2835_defconfig contains: > > CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE=y > > > > Likewise in the Foundation's downstream tree, bcmrpi_defconfig as well > > as bcm2711_defconfig and bcm2709_defconfig contain: > > CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE=y > > > > In contrast to this, we set the following on Revolution Pi devices: > > CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y > > > > Downclocking influences not only the uart1 baud rate but also the > > spi0 clock. We attach Ethernet chips to spi0, throughput was > > significantly worse with the ondemand governor (which is what we > > used previously). We felt that maximum Ethernet performance > > outweighs the relatively small powersaving gains. > > In that regard I suggest you use the upstream cpufreq driver which > behaves properly in that regard. It disables GPU freq scaling, so as to > change CPU frequencies without SPI/I2C/UART issues. Okay, I'll take a look. But the uart1 baudrate will still be wrong if the firmware downclocks because of overheating, right? Thanks, Lukas