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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 D44CCC43381 for ; Sun, 3 Mar 2019 19:13:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F9AC20830 for ; Sun, 3 Mar 2019 19:13:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="sTVsD7vI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726638AbfCCTNA (ORCPT ); Sun, 3 Mar 2019 14:13:00 -0500 Received: from mail-ot1-f67.google.com ([209.85.210.67]:38951 "EHLO mail-ot1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726541AbfCCTM7 (ORCPT ); Sun, 3 Mar 2019 14:12:59 -0500 Received: by mail-ot1-f67.google.com with SMTP id e15so2440620otk.6 for ; Sun, 03 Mar 2019 11:12:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=YbIdkywIH2VTWbLDmHSr4vQbZ6OY3Rh8ynYy3Ff1+4k=; b=sTVsD7vIpqBiS4eKHGMV+71YnqZNlmLsNgKkfeV9qhsJmX/d+95aD+isWWWhj3Fuqt NwuG7K13pnKs4MaZMowq90ssywlm5mFnv2BSStgSaHRiAQ5zDXvTz0z/64Y21fOs9mii 0d3AnMDErwm6FHkvhKaVUhcuIcnMzoe6YKAs16NJhE4bN0UuWgSH7p9TGJLY2HWI10dD +1FGiS5/V48BUCov9eg3xgBhVjH+6zJwtxtqjNFYkvaiFHiQOuSVvlHXtShJRe5flo9U FnK9CP7nOOz+oz0eVdM1hHJ5RCFz4VasDwT2RAQ/yIOWuYiIeW4ZxVCRB5ljn1587yKC VC2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=YbIdkywIH2VTWbLDmHSr4vQbZ6OY3Rh8ynYy3Ff1+4k=; b=Nshz4PsMaOGrfo1O2nJF+RmUvNUjBJ100hVD6Gk1cYVYt0raK0PHvGzy2J9pvqaOMv LrCdAp4C1/BH/3/91egHMnVri5vi1muZ3Ybyz9L8zBXq3wdR8ozCg+HQFc68c5sTcDSR UBmHPMXo1t7aBw81PYFzTHFN0F9Kc9GBuCuODEDKlBHyTdy6ZdOwBAZG+7Fu/O0avc5z ipr7xy5+BHtJ+X8dsGgC5CqISYyybs4wCZSVC2W/ggg9V3DVjleVgbOlLafTVpvZyKNA Few3RjDZGFC8234qlBC3AYFJRRTYqJrYXYmT9lYH5dPCIB+RCnFub3TiVss9NuKXsEB7 Xykg== X-Gm-Message-State: APjAAAVJncf789+Y/sDGAoOBgngtWFuqCVU15+3LRsb7NQmKVot7G/w/ ozTggSRgJMqKa4OEJ82kW8TKA6Zbx0L/PCByxX4= X-Google-Smtp-Source: APXvYqxa7yJClRVtt2XE1ZW+Eom5XYge+HqRvhHVJf4REvfpNReIunXq/jtyHWf4+o+2LYv1tzFLSjDcKR/Zz8Ts+4w= X-Received: by 2002:a9d:3f0:: with SMTP id f103mr7324489otf.223.1551640378271; Sun, 03 Mar 2019 11:12:58 -0800 (PST) MIME-Version: 1.0 References: <20190303122705.27094-1-katsuhiro@katsuster.net> <1623469.Hy6pdcMFRX@phil> <26c3aea3-959f-bfb3-177f-3e5314494361@katsuster.net> In-Reply-To: From: Tony McKahan Date: Sun, 3 Mar 2019 14:12:46 -0500 Message-ID: Subject: Re: [PATCH] arm64: dts: rockchip: decrease rising edge time of UART2 To: Katsuhiro Suzuki Cc: Heiko Stuebner , Akash Gajjar , Brian Norris , Christoph Muellner , Dmitry Torokhov , Douglas Anderson , Enric Balletbo i Serra , Ezequiel Garcia , Jakob Unterwurzacher , Klaus Goger , Levin Du , Linus Walleij , Manivannan Sadhasivam , Matthias Brugger , Oskari Lemmela , Robin Murphy , Shawn Lin , Shohei Maruyama , Tomeu Vizoso , Vicente Bergas , Viresh Kumar , linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 3, 2019 at 1:45 PM Tony McKahan wrote: > > Hello Katsushiro, And apologies for the extra "s", typing too quickly I'm afraid. > > On Sun, Mar 3, 2019 at 12:31 PM Katsuhiro Suzuki > wrote: > > > > Hello Tony, > > > > On 2019/03/04 0:13, Tony McKahan wrote: > > > On Sun, Mar 3, 2019 at 9:04 AM Katsuhiro Suzuki wrote: > > >> > > >> Hello Heiko, > > >> > > >> Thank you for comments. > > >> > > >> On 2019/03/03 22:19, Heiko Stuebner wrote: > > >>> Hi, > > >>> > > >>> Am Sonntag, 3. M=C3=A4rz 2019, 13:27:05 CET schrieb Katsuhiro Suzuk= i: > > >>>> This patch increases drive strength of UART2 from 3mA to 12mA for > > >>>> getting more faster rising edge. > > >>>> > > >>>> RockPro64 is using a very high speed rate (1.5Mbps) for UART2. In > > >>>> this setting, a bit width of UART is about 667ns. > > >>>> > > >>>> In my environment (RockPro64 UART2 with FTDI FT232RL UART-USB > > >>>> converter), falling time of RockPro64 UART2 is 40ns, but riging ti= me > > >>>> is over 650ns. So UART receiver will get wrong data, because recei= ver > > >>>> read intermediate data of rising edge. > > >>>> > > >>>> Rising time becomes 300ns from 650ns if apply this patch. This is = not > > >>>> perfect solution but better than now. > > >>>> > > >>>> Signed-off-by: Katsuhiro Suzuki > > >>>> --- > > >>>> arch/arm64/boot/dts/rockchip/rk3399.dtsi | 9 +++++++-- > > >>>> 1 file changed, 7 insertions(+), 2 deletions(-) > > >>> > > >>> your changing a core rk3399 property here, so I'd really like to ge= t > > >>> input from other board stakeholders on this before applying a core > > >>> change. > > >>> > > >>> Could you either include the submitters of other rk3399-boards in t= he > > >>> recipient list so that they're aware or limit the change to rockpro= 64 for > > >>> the time being (aka overriding the property in the board-dts) pleas= e? > > >>> > > >> > > >> OK, I'm adding other boards members. > > >> by ./scripts/get_maintainer.pl arch/arm64/boot/dts/rockchip/rk3399-*= .dts > > >> > > >> > > >> RockPro64 directly connect UART2 pins of RK3399 to external connecto= r. > > >> I think maybe other RK3399 boards are facing same problem, but I can= not > > >> check it because I have RockPro64 only... > > >> > > >> I'm happy if someone tell me other boards situation. > > > > > > I'm pulling out other rockchip boards momentarily to see what kind of > > > population we have. > > > > > > Note these are not all running 5.x kernels, however none of them have > > > the UART2 drive levels modified to my knowledge, and regardless, none > > > show over 100 ns. > > > > > > board: rise/fall > > > > > > rk3399-roc-pc: 90ns/90ns > > > rk3399-rockpro64 V2.0: 90ns/45ns > > > rk3399-rockpro64 V2.1: 40ns/41ns > > > > > > Please make sure there's not a large amount of flux or something > > > around the terminals on your board, that seems excessively high. > > > > > > > Thank you for valuable information. For more deeply discussion, > > I tried other conditions and watch the rise/fall times. > > > > 1) Not connect > > The rise/fall times are 40ns/5ns when nothing connect (impedance is > > very high) to external pin of RockPro64. > > > > What UART device are you using with RockPro64? If you use some device > > with RockPro64 and board shows rise/fall times =3D 90ns/45ns, my device > > is not suitable for RockPro64 by some reason. So it's better to drop > > my patch. > > The adapter is an FTDI FT232RL breakout board, attached with some > generic Dupont connector jumpers. > Interesting your RockPro is showing this symptom, perhaps there is a > cold solder joint somewhere introducing resistance? > > > > > 2) Other SoC > > I have other SoC board rk3328-rock64, Rock64 shows rise/fall times =3D > > 90ns/80ns when same UART-USB device is connected to UART pin. > > I measured similar on my Rock64 as well. > > > > > I think it shows rk3399's (or RockPro64's?) drive strength is a little > > weak. So it's better to increase the drive strength of UART of rk3399. > > I do not think this is a bad idea generally, it simply allows for more > available current from the interface. I'll let others be the judge of > that, however. > > > > > Best Regards, > > Katsuhiro Suzuki > > > > >> > > >> Best Regards, > > >> Katsuhiro Suzuki > > >> > > >> > > >>> Thanks > > >>> Heiko > > >>> > > >>> > > >>> > > >>>> diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64= /boot/dts/rockchip/rk3399.dtsi > > >>>> index beaa92744a64..e3c8f91ead50 100644 > > >>>> --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi > > >>>> +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi > > >>>> @@ -2000,6 +2000,11 @@ > > >>>> drive-strength =3D <8>; > > >>>> }; > > >>>> > > >>>> + pcfg_pull_up_12ma: pcfg-pull-up-12ma { > > >>>> + bias-pull-up; > > >>>> + drive-strength =3D <12>; > > >>>> + }; > > >>>> + > > >>>> pcfg_pull_up_18ma: pcfg-pull-up-18ma { > > >>>> bias-pull-up; > > >>>> drive-strength =3D <18>; > > >>>> @@ -2521,8 +2526,8 @@ > > >>>> uart2c { > > >>>> uart2c_xfer: uart2c-xfer { > > >>>> rockchip,pins =3D > > >>>> - <4 RK_PC3 RK_FUNC_1 &pcfg_pul= l_up>, > > >>>> - <4 RK_PC4 RK_FUNC_1 &pcfg_pul= l_none>; > > >>>> + <4 RK_PC3 RK_FUNC_1 &pcfg_pul= l_up_12ma>, > > >>>> + <4 RK_PC4 RK_FUNC_1 &pcfg_pul= l_none_12ma>; > > >>>> }; > > >>>> }; > > >>>> > > >>>> > > >>> > > >>> > > >>> > > >>> > > >>> > > >>> > > >> > > >> > > >> _______________________________________________ > > >> Linux-rockchip mailing list > > >> Linux-rockchip@lists.infradead.org > > >> http://lists.infradead.org/mailman/listinfo/linux-rockchip > > > > > > > >