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,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 11678C433E1 for ; Thu, 13 Aug 2020 13:04:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD1DF2078D for ; Thu, 13 Aug 2020 13:04:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=melexis.com header.i=@melexis.com header.b="WmO83z/B" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726102AbgHMNEb (ORCPT ); Thu, 13 Aug 2020 09:04:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57498 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726053AbgHMNE0 (ORCPT ); Thu, 13 Aug 2020 09:04:26 -0400 Received: from mail-io1-xd42.google.com (mail-io1-xd42.google.com [IPv6:2607:f8b0:4864:20::d42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B4F6C061757 for ; Thu, 13 Aug 2020 06:04:26 -0700 (PDT) Received: by mail-io1-xd42.google.com with SMTP id b17so7168301ion.7 for ; Thu, 13 Aug 2020 06:04:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=melexis.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=EyT6hXIz8JrsQFCCctkkiHVgguQyJ1gofAulsUuUyq8=; b=WmO83z/BitpSIuCu2kRA4IL0r0q4BCCp01aaBGq36Zl5TqGTv53D5VjB6N2cTeJxQR +zTO5/GPXRd34NMbmY55Dvvaz4EX1wEcrKsAxYCiVLygJ0T7dYG5MFaYwqM4hE6E7fhQ 7k4M5SF9xD48OcMzXDwpyp6CcDjJmkgdUlNa2aw2OJMoX4CdkyVelJDrHQP6CrVVA5gm npXyvKpBVmSpTx6qKGLoTPbDRp5SQZ1/FJsVVh3IsjDj8fc46koKh/X4Kj2q/i0ayTbg 85ZdehJ9O7TXMilqC3phRhc0hvOuR77rDiARxJCJ7FNYTKDk+WaaB9CAxsrsVRZyVmmB o3iA== 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; bh=EyT6hXIz8JrsQFCCctkkiHVgguQyJ1gofAulsUuUyq8=; b=Q86gjOeiwDT0vTmLV2oEm06jcNRH9z0VntHmzFNvJoe5ObZTqA3N9C8wAm34Jo5546 lkj8vPGxMFP9qBszQNRfBl4aCj3s+QhfNDuLgOLl5M5V0AflroaciR9iecLI+VDpWzqm w5kkpkzTTnhFamtgzqCd0ze9WscnbHdYGU0oGva7wDsOF8hFznS9ALNiNTMFapn8CWaK IpoxRx8xHdRxADtktPJXIA9pLPJLu5OAcllcBosWnp1ChFfn2lFsN1NmeDLOt3SREe+i siWMa9M/Rr9UDoIMofUku3mK+9kTOMiFUE9uufwOHo9rj/VqqpFBtrAOkeNyxYprhNfB 9KUg== X-Gm-Message-State: AOAM533D2osqajpnA5OlsA1OZ2mEPQ+X/lqihUu8uVqHx7jIgmwQDQBp xRSX4lTNDeUKLTgn7xmrsAskAhwGRLsgB+GX47GaFw== X-Google-Smtp-Source: ABdhPJxcJYj5jf2h4KNmEen8sLv5g1GkvODF96sNVcyCS+zBw5jWNYDrUE1VwnR0GjgyLgBD4kG20pQcBFC2UXc47V4= X-Received: by 2002:a5e:dd4c:: with SMTP id u12mr4514913iop.93.1597323864338; Thu, 13 Aug 2020 06:04:24 -0700 (PDT) MIME-Version: 1.0 References: <20200813075125.4949-1-cmo@melexis.com> <20200813075125.4949-4-cmo@melexis.com> In-Reply-To: From: Crt Mori Date: Thu, 13 Aug 2020 15:03:48 +0200 Message-ID: Subject: Re: [PATCH v5 3/5] iio:temperature:mlx90632: Convert polling while loop to do-while To: Andy Shevchenko Cc: Jonathan Cameron , linux-iio , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Thu, 13 Aug 2020 at 13:24, Andy Shevchenko wrote: > > On Thu, Aug 13, 2020 at 2:14 PM Crt Mori wrote: > > > > On Thu, 13 Aug 2020 at 13:03, Andy Shevchenko wrote: > > > > > > On Thu, Aug 13, 2020 at 10:53 AM Crt Mori wrote: > > > > > > > > Reduce number of lines and improve readability to convert polling while > > > > loops to do-while. The iopoll.h interface was not used, because we > > > > require more than 20ms timeout, because time for sensor to perform a > > > > measurement is around 10ms and it needs to perform measurements for each > > > > channel (which currently is 3). > > > > > > I don't see how it prevents using iopoll.h. It uses usleep_range() > > > under the hood in the same way you did here, but open coded. > > > > > > > One loop is indeed 10ms and that is not the problem, the problem is > > that timeout is at least 3 calls of this data ready (3 channels), so > > that is at minimum 30ms of timeout, or it could even be 4 in worse > > case scenario and that is outside of the range for usleep to measure. > > So in case of the other loop, where we wait 200ms for channel refresh > > it is also out of scope. Timeout should be in number of tries or in > > msleep range if you ask me. > > I still didn't buy it. You have in both cases usleep_range(). Why in > your case it's okay and in regmap_read_poll_timeout() is not? > I tried and it did not work, so then I read the manual. Looking into * regmap_read_poll_timeout_atomic - Poll until a condition is met or a timeout occurs ... * @delay_us: Time to udelay between reads in us (0 tight-loops). * Should be less than ~10us since udelay is used * (see Documentation/timers/timers-howto.rst). * @timeout_us: Timeout in us, 0 means never timeout So I went to read Documentation/timers/timers-howto.rst SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms): * Use usleep_range - Why not msleep for (1ms - 20ms)? Explained originally here: http://lkml.org/lkml/2007/8/3/250 msleep(1~20) may not do what the caller intends, and will often sleep longer (~20 ms actual sleep for any value given in the 1~20ms range). In many cases this is not the desired behavior. Since I am above the 20ms range, it is too much for usleep_range and that proved to be a case as I got -ETIMEOUT and the desired channels were not read. > > > ... > > > > > > > - while (tries-- > 0) { > > > > + do { > > > > ret = regmap_read(data->regmap, MLX90632_REG_STATUS, > > > > ®_status); > > > > if (ret < 0) > > > > return ret; > > > > - if (reg_status & MLX90632_STAT_DATA_RDY) > > > > - break; > > > > usleep_range(10000, 11000); > > > > - } > > > > + } while (!(reg_status & MLX90632_STAT_DATA_RDY) && tries--); > > > > > > > > if (tries < 0) { > > > > dev_err(&data->client->dev, "data not ready"); > > -- > With Best Regards, > Andy Shevchenko