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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6E1D3C433E2 for ; Thu, 16 Jul 2020 19:26:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BA222074B for ; Thu, 16 Jul 2020 19:26:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="l6V/ZjkL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729010AbgGPT00 (ORCPT ); Thu, 16 Jul 2020 15:26:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37192 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728788AbgGPT0Z (ORCPT ); Thu, 16 Jul 2020 15:26:25 -0400 Received: from mail-ua1-x92b.google.com (mail-ua1-x92b.google.com [IPv6:2607:f8b0:4864:20::92b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBBCDC061755 for ; Thu, 16 Jul 2020 12:26:24 -0700 (PDT) Received: by mail-ua1-x92b.google.com with SMTP id k7so2120433uan.13 for ; Thu, 16 Jul 2020 12:26:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=mMbgdwDtP27CXsZjfhivFu9jhDR9mwGH1nJkgK5VWA4=; b=l6V/ZjkLcriHPckaGAhCydz/u19BsZgYcCww8XquYbbpy5LwQvsEWbqNtQ9EHakqEW vXH9XTjUY4vxOFStBVSXVpm6d3Jdn27EKaGP30cCRQRoYAuETmq0ozpX+VS9nhMH9rb2 MOazxwCuiazGuB3DfmDvxEd4oX7NFNcL+Ebtw+JyABM5qVCmJGvS88PZ33uoL66o5RjE DHUXc4md7s5yo7o1e7NnC71uCaRCAquHQ8jn1UiupyKnXgfEWaOGIMpGKCCMlcNVtdxT NI0DLeDDQLr+iDd0LlmVV6L1CF2MMf1uKeiaxNBaEfYUQLXsLJWDdY8nPE3EGrZFkqWn 0K/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=mMbgdwDtP27CXsZjfhivFu9jhDR9mwGH1nJkgK5VWA4=; b=Zta5aiV5LbbPYbfvDYb6tkjuc8V5/LtaXeGycLU4L8jAcwli2SED1svNbvZ1Ez1lN1 m3+0pUZVfTB2vrCx6QB3KgctBiniy8LGtH6NuymjG4v4u3bcUbZhD+sjJaH0Ilum3jYH 72XRPEtIvUY0k/r9gN/yyyzO7mx6/RuoRsQ6bPon3XzCn1GTWRKCgvNtbhA3CMBN8Yqt ggJPIN/sf6zHnnvfVm6awoj0gbcv4m7A4S6btyiMf6bFVi5MTXx0QJIGgouKKOc3FeB9 zS1pyDrDyrYXkqyYLkMZVyNHx4U7HeDYiyz2UgqwLq8hjy/C7QY61ha8xoikteXaRHFV aPZQ== X-Gm-Message-State: AOAM530rLwHUdrrLTSucmp5CakTe1lo3XCZnaFlcM/JeW6mjfza/Xv3D orxwuLnBnt/K4/tlq6r28kFs8/z4AQeht9mmZqPYXg== X-Google-Smtp-Source: ABdhPJxI27D2ZjgmllSiN9CyNj2NIN/I6IAP4IKY7/3C7HSigJuRY8/xn/dM8qDCzz1k5QaZPDzYGw5UVzYmXAI4ZSg= X-Received: by 2002:ab0:55da:: with SMTP id w26mr4372735uaa.28.1594927584029; Thu, 16 Jul 2020 12:26:24 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a67:fd69:0:0:0:0:0 with HTTP; Thu, 16 Jul 2020 12:26:23 -0700 (PDT) In-Reply-To: References: From: Itai Handler Date: Thu, 16 Jul 2020 22:26:23 +0300 Message-ID: Subject: Re: Serial port driver usage and status To: Michel Macena Oliveira Cc: linux-rt-users@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org Hi Michel, On 7/16/20, Michel Macena Oliveira wrote: > Hi, sorry for my newbie question, > What is the status of the serial port driver? > I've written some code to use serial ports for the generic kernel linux, > And now I want to write something similar for the real time kernel, do > I have to use some specific library, flags or something or is it just > the same settings? > > I'm asking because now I need to take into account the serial access > in the scheduler to ensure a real time behavior . > > Any help, advice, hint or tips would be appreciated. > Do you mean that you wrote some code that works with a /dev/tty* serial port? In some kernel versions (e.g 4.19) we saw high latencies in the rx path of serial drivers. I think that this is due to rx handled in the context of a workqueue which also handles other system activities. We found a workaround to this problem. If I remember correctly we create a dedicated thread for the port and assign it a high priority. Itai Handler