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=-7.0 required=3.0 tests=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 B9930C43381 for ; Sun, 3 Mar 2019 14:03:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8AD7020823 for ; Sun, 3 Mar 2019 14:03:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726347AbfCCODd (ORCPT ); Sun, 3 Mar 2019 09:03:33 -0500 Received: from www1102.sakura.ne.jp ([219.94.129.142]:44016 "EHLO www1102.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726250AbfCCODd (ORCPT ); Sun, 3 Mar 2019 09:03:33 -0500 Received: from fsav401.sakura.ne.jp (fsav401.sakura.ne.jp [133.242.250.100]) by www1102.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x23E3Tkc002807; Sun, 3 Mar 2019 23:03:30 +0900 (JST) (envelope-from katsuhiro@katsuster.net) Received: from www1102.sakura.ne.jp (219.94.129.142) by fsav401.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav401.sakura.ne.jp); Sun, 03 Mar 2019 23:03:29 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav401.sakura.ne.jp) Received: from [192.168.1.2] (119.104.232.153.ap.dti.ne.jp [153.232.104.119]) (authenticated bits=0) by www1102.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x23E3TnS002800 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Sun, 3 Mar 2019 23:03:29 +0900 (JST) (envelope-from katsuhiro@katsuster.net) Subject: Re: [PATCH] arm64: dts: rockchip: decrease rising edge time of UART2 To: 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 Cc: linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20190303122705.27094-1-katsuhiro@katsuster.net> <1623469.Hy6pdcMFRX@phil> From: Katsuhiro Suzuki Message-ID: Date: Sun, 3 Mar 2019 23:03:29 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <1623469.Hy6pdcMFRX@phil> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Heiko, Thank you for comments. On 2019/03/03 22:19, Heiko Stuebner wrote: > Hi, > > Am Sonntag, 3. März 2019, 13:27:05 CET schrieb Katsuhiro Suzuki: >> 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 time >> is over 650ns. So UART receiver will get wrong data, because receiver >> 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 get > input from other board stakeholders on this before applying a core > change. > > Could you either include the submitters of other rk3399-boards in the > recipient list so that they're aware or limit the change to rockpro64 for > the time being (aka overriding the property in the board-dts) please? > 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 connector. I think maybe other RK3399 boards are facing same problem, but I cannot check it because I have RockPro64 only... I'm happy if someone tell me other boards situation. 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 = <8>; >> }; >> >> + pcfg_pull_up_12ma: pcfg-pull-up-12ma { >> + bias-pull-up; >> + drive-strength = <12>; >> + }; >> + >> pcfg_pull_up_18ma: pcfg-pull-up-18ma { >> bias-pull-up; >> drive-strength = <18>; >> @@ -2521,8 +2526,8 @@ >> uart2c { >> uart2c_xfer: uart2c-xfer { >> rockchip,pins = >> - <4 RK_PC3 RK_FUNC_1 &pcfg_pull_up>, >> - <4 RK_PC4 RK_FUNC_1 &pcfg_pull_none>; >> + <4 RK_PC3 RK_FUNC_1 &pcfg_pull_up_12ma>, >> + <4 RK_PC4 RK_FUNC_1 &pcfg_pull_none_12ma>; >> }; >> }; >> >> > > > > > >