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 070D4C433E1 for ; Fri, 14 Aug 2020 07:33:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D60C720829 for ; Fri, 14 Aug 2020 07:33:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=melexis.com header.i=@melexis.com header.b="F02m6Db+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726455AbgHNHdW (ORCPT ); Fri, 14 Aug 2020 03:33:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726006AbgHNHdV (ORCPT ); Fri, 14 Aug 2020 03:33:21 -0400 Received: from mail-io1-xd41.google.com (mail-io1-xd41.google.com [IPv6:2607:f8b0:4864:20::d41]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C85BFC061757 for ; Fri, 14 Aug 2020 00:33:21 -0700 (PDT) Received: by mail-io1-xd41.google.com with SMTP id g19so9889924ioh.8 for ; Fri, 14 Aug 2020 00:33:21 -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=P0QNUADYgOn/C/m3nQ6Y5G9JAzArzh2nTxmJSP8VeEc=; b=F02m6Db+bn1IYiEMLwRmkwBmNHsUDL69Su3uR7D6wPUjYyekdJ2OdpB5LNiRNFplCI N4Y06rHa5Oz0P+GDzULkqcJ8BTWxuh5DIJ/9zitlUFE14XPSWRPplKQXlAjCkkowoCQm xp1YMzD2Efau1+2DVcsFgGTCkfiu/z3HBRC1lNWxygPRNIZHBsS8FJBrzknX4Nl/C4cL C8ApAiyOEkspIrd8MTeqeollAxgrXFMaAMh2pCU+9anHjE81lYAOzXNd0tJyemg5AjtZ La6rs8+EfmZ+0HH5UYvpXhCrR7pdznxhZpXcnlfz/LhM9glHxr87smK2Jn3joeTR46I2 NOEQ== 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=P0QNUADYgOn/C/m3nQ6Y5G9JAzArzh2nTxmJSP8VeEc=; b=pDQ+mUzrYCktyZ2DakxSKi2s4TVn4JGTQglMTyi5Oiy8LFwWMFJhMbdg9C/iVdYrkx CxOwZemjJvDiGR25AQNMtIUwq6RpjCBSRS92x0nA9qzPXijg4mHA9EEDTlSJs76/UGqe VOV3p9Ofiw0BiLWmdlNW4A0tRzWnYigaHX4BMvMZaOe0E850rkmpMkf8u5n3aqK3rimY wgK7ylUbNSpwKJu5E3y28m+WQ9o2iQ6GrA1GIXeTSMwbghlPi69uOtwvDR5zyDNgP/P7 sB38TWH8lWzWXDUxBQah5f4QhhB+QDTJjuCzVZeWL4ikY3Q2J3XQddN65mPT0yQXNjyM RMDw== X-Gm-Message-State: AOAM533ObYSKX7ylCF2O9tUMN8hUHelwBlPZlbxe2R/P/+//DeDMGWnK soE4r+MCmbeKUJ9Si44ND8XUKenCi+p5GodPhl/10w== X-Google-Smtp-Source: ABdhPJw1TGYdJE6viPoHF/fq98yJWPlG5/W+SzRg1+zNI/JE5qYMT9Y9X6wH9ta4mk7G4xrhP4Mw7x2BUEwvhKVypEc= X-Received: by 2002:a5d:8cce:: with SMTP id k14mr1184502iot.13.1597390401084; Fri, 14 Aug 2020 00:33:21 -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: Fri, 14 Aug 2020 09:32:45 +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 21:41, Andy Shevchenko wrote: > > On Thu, Aug 13, 2020 at 4:04 PM Crt Mori wrote: > > 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: > > ... > > > > > > 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 > > Why _atomic?! I just pasted something, it is the same as for non _atomic > > > ... > > * @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); > > You use here usleep_range(). The same is used for > regmap_read_poll_timeout(). What's the difference? > > Since it uses 1/4 of the range you probably need to update tries and > timeout_us to make it work. > Timeout_us here needs to be in one case 100 * 10ms (maybe not realistic as we could live with number of around 40 * 10ms), but this is a lot more than proposed range of usleep which Is up to 20ms. Even in best case this timeout should be 40 ms to give enough time to measure 2 channels for sure. So with the current timeout_us requirement we are outside of the range of the udelay timer and that is why I would need a macro with number of tries, not with the timeout value (or timeout value of ms). > > > > > > - } > > > > > > + } while (!(reg_status & MLX90632_STAT_DATA_RDY) && tries--); > > > > > > > > > > > > if (tries < 0) { > > > > > > dev_err(&data->client->dev, "data not ready"); > > -- > With Best Regards, > Andy Shevchenko