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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E1D5C0015E for ; Fri, 28 Jul 2023 19:00:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229799AbjG1TAE convert rfc822-to-8bit (ORCPT ); Fri, 28 Jul 2023 15:00:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229572AbjG1TAD (ORCPT ); Fri, 28 Jul 2023 15:00:03 -0400 Received: from gloria.sntech.de (gloria.sntech.de [185.11.138.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35E9F30F7; Fri, 28 Jul 2023 12:00:00 -0700 (PDT) Received: from [185.230.175.137] (helo=phil.localnet) by gloria.sntech.de with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1qPSgp-0000vt-Fe; Fri, 28 Jul 2023 20:59:51 +0200 From: Heiko Stuebner To: Peter Geis , Javier Martinez Canillas Cc: linux-kernel@vger.kernel.org, Peter Robinson , Caleb Connolly , Jarrah Gosbell , Krzysztof Kozlowski , Martijn Braam , Ondrej Jirman , Rob Herring , Tom Fitzhenry , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org Subject: Re: [PATCH] arm64: dts: rockchip: Change serial baud rate for Pinephone Pro to 1.5 MB Date: Fri, 28 Jul 2023 20:59:50 +0200 Message-ID: <4495367.TLkxdtWsSY@phil> In-Reply-To: <87pm4kuanl.fsf@minerva.mail-host-address-is-not-set> References: <20230403175937.2842085-1-javierm@redhat.com> <3797122.KgjxqYA5nG@diego> <87pm4kuanl.fsf@minerva.mail-host-address-is-not-set> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Javier, Am Samstag, 22. Juli 2023, 01:06:54 CEST schrieb Javier Martinez Canillas: > Heiko Stübner writes: > > Am Dienstag, 18. April 2023, 14:11:53 CEST schrieb Javier Martinez Canillas: > >> Heiko Stübner writes: > >> > Am Dienstag, 4. April 2023, 14:52:02 CEST schrieb Peter Geis: > >> >> On Tue, Apr 4, 2023 at 3:55 AM Heiko Stübner wrote: > >> >> > Am Montag, 3. April 2023, 19:59:37 CEST schrieb Javier Martinez Canillas: > >> >> > > This baud rate is set for the device by mainline u-boot and is also what > >> >> > > is set in the Pinebook Pro Device Tree, which is a device similar to the > >> >> > > PinePhone Pro but with a different form factor. > >> >> > > > >> >> > > Otherwise, the baud rate of the firmware and Linux don't match by default > >> >> > > and a 'console=ttyS2,1500000n8' kernel command line parameter is required > >> >> > > to have proper output for both. > >> >> > > >> >> > The interesting question is always if this will break someone else's setup. > >> >> > I've never really understood the strange setting of 1.5MBps, but on the > >> >> > other hand it _is_ a reality on most boards. > >> > > >> >> The 1.5M baud is default because the clock structure on rockchip > >> >> devices does not allow a clean 115200 baud. By attempting to force > >> >> 115200, it will always be slightly off (either low or high depending > >> >> on how the driver decided to round). If this actually causes any > >> >> problems is the subject of much debate. > >> > > >> > thanks so much for this piece of clock-detail. As I wrote, I never really > >> > understood the why _before_ but also never cared that much to dive > >> > into it and find out. > >> > > >> > So your explanation closes one knowledge gap in my head. > >> > > >> > Thanks a lot :-) > >> > >> Did you make a decision about this? I guess the clock explanation is yet > >> another argument in favour of switching the PPP to a 1.5 Mbps baud rate ? > > > > Sorry, but no decision made here. Either way it's breaking for someone, > > which makes this quite hard. > > > > Another ping on this patch. > > > The rate accuracy is the one side, the two-boot issue is the other side. > > And mainline u-boot (and levinboot - whatever that is) provides a 3rd side. > > > > People starting with the phone probably won't replace the bootloader > > in a first step but instead might play with a system image or newer kernel. > > So if the uart will break for everyone using the default bootloader from > > the factory that is somewhat bad. > > > > Probably won't replace the DTB shipped with the firmware either? If one is > replacing the firmware provided DTB witch the one in the mainline kernel, > probably such person is also using mainline u-boot? Not necessarily. I.e. putting an extlinux.conf on an sd-card with a kernel-image and dtb is not rocket science ;-) > > I don't have a Pinephone Pro myself, so I really hoped for some Acks > > or similar to appear in the meantime. > > > > For someone like me who is only using mainline u-boot, linux, etc then > having a consistent uart baud rate across all components is really useful. > > Otherwise I either have serial console for u-boot or the kernel, but can't > have both working so is annoying. > > It would be good to have a definite answer on this. Since every time that > I try to hack on my PPP, I end changing my DTS and remember this patch :) So far people only reported "breaks my setup". I'm in a pickle here ;-) . Without anybody saying "I want to also move into this direction" I really feel I should not merge a patch that breaks other peoples setups. Heiko