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 AC9D0C433DF for ; Thu, 13 Aug 2020 19:41:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8909320791 for ; Thu, 13 Aug 2020 19:41:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="pAvjxfRp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726557AbgHMTlE (ORCPT ); Thu, 13 Aug 2020 15:41:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726334AbgHMTlE (ORCPT ); Thu, 13 Aug 2020 15:41:04 -0400 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2DB5C061757; Thu, 13 Aug 2020 12:41:03 -0700 (PDT) Received: by mail-pj1-x1041.google.com with SMTP id ha11so3240353pjb.1; Thu, 13 Aug 2020 12:41:03 -0700 (PDT) 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; bh=0ItWqBHS3w4jy5wn4p04F1o5bOPDbMS03wqOneXGD2w=; b=pAvjxfRpO04XR0yxwLloK2cUKe3FTLgE9OBjc/0k39x1lb1VE0hjqlv+bvc9IkffKw ohcZ3HcTN/J8jKsJH9UMIWVs7yDAxfq4TtxmlItOeQALNzNb4cADGB1vllk2emMv8g3t /9+YiQOL+Nz0jnrED0b5TpDp1E7u0A23uI6+oDawQzCGa2KcpTS/MT1pNJBZL6UT1gCK uosSAPCvfaxgsNJSdVNtnhUtiZv9wIe2dPOBMe9ogrU7jbmCzgFQtmzUdCChbvG2VefL coajWmbmOZRNc7x4+5l4hEWmOsI8QjEA+7+uCwh+Hg/PFsojVsjnXfYSb8QxwfDwrlzk LYeA== 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=0ItWqBHS3w4jy5wn4p04F1o5bOPDbMS03wqOneXGD2w=; b=TGKNCoD+QrLXvPMLXKRobEpcZCvxZRL3puEgZ7lhnIlnP1U2gsuP5pGCReZRJ15dzw jszu31eBuKRqz/eOSDq0qKJBW2FnUC/NVZdylACjgZvWHGhDzG9E8BI0Fyoz5Hm/3iJY NU75TAqskhCVwt6QoAF/tYyicgcAESPDDme4fIQ7Q38rX/VcmhPTiftJH5NIsAJlxnxH C3PKnivu+sB/vGgPgwh1+fv0KG0hbHssIBUk3iXSu4vwvFDqctw7mOca8STmO8VBCU/0 HT7mYRXEo6bHP1LgdyGeKQDC+mzH39XxGmYj4c44/lhZp9l2ND3K5v53In+yfrGeRiok u7Rg== X-Gm-Message-State: AOAM5308Ao5jQ/C2DAij7JkYGKgaf9uhPLRI054uz56eiDjmOsYOb/pA tBHsKoW6IDhIWlGI8WeiTzCudz4aScSxLH1UYRP8foVUbfc= X-Google-Smtp-Source: ABdhPJy2rnCAGpf1YLxMoHo84kHU8QJ01pqvdjAcecx4qOd6Y0/r5k9Cv9x3aJSz/r4b2d9pfVtmJUAeffc+M2z0AYw= X-Received: by 2002:a17:90b:509:: with SMTP id r9mr4074225pjz.228.1597347663347; Thu, 13 Aug 2020 12:41:03 -0700 (PDT) MIME-Version: 1.0 References: <20200813075125.4949-1-cmo@melexis.com> <20200813075125.4949-4-cmo@melexis.com> In-Reply-To: From: Andy Shevchenko Date: Thu, 13 Aug 2020 22:40:47 +0300 Message-ID: Subject: Re: [PATCH v5 3/5] iio:temperature:mlx90632: Convert polling while loop to do-while To: Crt Mori 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, 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?! > ... > * @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. > > > > > - } > > > > > + } while (!(reg_status & MLX90632_STAT_DATA_RDY) && tries--); > > > > > > > > > > if (tries < 0) { > > > > > dev_err(&data->client->dev, "data not ready"); -- With Best Regards, Andy Shevchenko