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,URIBL_BLOCKED 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 5B70AC433E1 for ; Fri, 14 Aug 2020 09:42:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 25B6A20866 for ; Fri, 14 Aug 2020 09:42:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=melexis.com header.i=@melexis.com header.b="OjMGGmCA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726730AbgHNJmo (ORCPT ); Fri, 14 Aug 2020 05:42:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726091AbgHNJmo (ORCPT ); Fri, 14 Aug 2020 05:42:44 -0400 Received: from mail-io1-xd43.google.com (mail-io1-xd43.google.com [IPv6:2607:f8b0:4864:20::d43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 214ACC061383 for ; Fri, 14 Aug 2020 02:42:44 -0700 (PDT) Received: by mail-io1-xd43.google.com with SMTP id j8so10136023ioe.9 for ; Fri, 14 Aug 2020 02:42:44 -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=AspIN0mKod2D4fw11QEsKNtq92S2lAnwdSlAe9wE40U=; b=OjMGGmCAnlktilu79lmfTPRv171f69fT08t+qaQHMbxST6z2QcobCk+RVa/GghD+yU DAyHdImgAJzstNveAnXYZOBN7x1H/qNSzO0EFR+arDrYvNNKXc/SYbQAeDmDqIRmpoAk lvWHRDoTAMiSLkYznS8jqsVqafYK93TAAnVbKFXJHyXOoX7YTPCI+1SX/v7r1uACPxdO UVmSxllGDoXzSVNfOUo2bPx7xzG7OjSjziJIg/IUhkqPBtDoE88XG/9ip+WphUeIK5hJ hdC6dirSin7v/WnXEUl1RFT/H/l4+xc+8KVIYJLjoPI6zSuZz3mqsmsItqiHWFkoe07g Yq1g== 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=AspIN0mKod2D4fw11QEsKNtq92S2lAnwdSlAe9wE40U=; b=tRDKUaaaYX3ZkMUkG+V6+Y6K/zozTIjIojWJTNJPLVP02KCRPbTQg0V73hRoIZ5j0a on2aqe2KrJUEz+y7l5KJiy4cDnb2do9Ks0N6mVaBNjdHj7EaCSkJOZ2kM5H9C5Ru07ly og7wRd2OWQ4q8+BTF+ousQc8ZFdiJo1zh8Do/8ss3eBpZLHAOaFWb41qo3fCOg8r1Ukg OLxStfd/2OvfYpAKjdPOdUI5psgazhg838ltPtbI6RAlFl7StUDAF7KYDFtSncAKKfHH DthYxlyT/QWvHVvFkPRH/jk7hOGOQJHEzJtKBfRlbV35paYlwtOeMns9CiX7wyAeWlPJ qhEQ== X-Gm-Message-State: AOAM531xk4Z5Xsiz4WDkHKFzOBZ5AAE5GmeJtGho4no8dkgKp114vuc7 9Bdo3CE/QRKpn+B1zZOqo6AqK8V5hmughOLA2opFJw== X-Google-Smtp-Source: ABdhPJyYHB4rlqQ6DIvZ/ZMd0V4MEKTcbHltccZZWTakaQmZcA7txa+DPHXLYXpSb3gVaHKSG5qHFkmgdAqh2fjAfUo= X-Received: by 2002:a6b:ba89:: with SMTP id k131mr1443918iof.133.1597398163441; Fri, 14 Aug 2020 02:42:43 -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 11:42:07 +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 Fri, 14 Aug 2020 at 11:32, Andy Shevchenko wrote: > > On Fri, Aug 14, 2020 at 10:33 AM Crt Mori wrote: > > 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 > > OK. > > ... > > > > > * @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 > > ... > > > > > > > > > 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). > > I do not understand. The regmap_read_poll_timeout() is a macro which > unrolls in the very similar loop you have now in the code. > What prevents it from using it? > > I think there is a big misunderstanding about the parameters of that macro. > delay_us (must be small enough), timeout_us can be any long. > I tested on Beaglebone with the 100 * 10000 as timeout_us and I always got the -ETIMEDOUT error. I also tested in the other case where delay_us is 250000 and then timeout_us would be 4*250000 and I have also received -ETIMEDOUT as a response. I can prepare a patch with the iopoll.h API and maybe you will spot the mistake, as after rechecking timeout_us is indeed 64bit and is only used in the time comparison operations and not with timers. > -- > With Best Regards, > Andy Shevchenko