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=-2.7 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 B066BC4338F for ; Mon, 23 Aug 2021 14:51:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 918266102A for ; Mon, 23 Aug 2021 14:51:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230186AbhHWOwI (ORCPT ); Mon, 23 Aug 2021 10:52:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35384 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229726AbhHWOwI (ORCPT ); Mon, 23 Aug 2021 10:52:08 -0400 Received: from mail-wm1-x32c.google.com (mail-wm1-x32c.google.com [IPv6:2a00:1450:4864:20::32c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44CD3C061575 for ; Mon, 23 Aug 2021 07:51:25 -0700 (PDT) Received: by mail-wm1-x32c.google.com with SMTP id u1so10745938wmm.0 for ; Mon, 23 Aug 2021 07:51:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:subject:from:to:cc:date:in-reply-to:references :user-agent:mime-version:content-transfer-encoding; bh=kur3RBD8vN5RjLBs9syNU8xwMW+dc26V4IavA+uRaEo=; b=htYRb3Xgqb+Iiedc3WC2bp8QsCoP0NiUDxmFqCP4sIroAY2Xt10gBQ90cFQ5s3Hkni G8AWUX/qKQYQH3MbI6GXgt3Z0Gg9SecEIsgoqOhH6E9dNvLvlNzUPKIwITk1uQgYzqFz UxPs549E6rq7UYjGh1bJDc+fQUCNh5HiDF0nrDiczRrQSY1zlBuXHAMiDVLqBrNsYNlA ehI7TuA/8e5nmlf9YS8YoWMXvIATds/csYCOqWuzdjfU9dtHsTa54sKly3y82J6/4vna Pa9IkaFWmVz2iu+eSA/0Z0D65T8Zq2a4mi5/2nH7E4FO4reNB+pybC8jcO9cH7qSytWa xhAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=kur3RBD8vN5RjLBs9syNU8xwMW+dc26V4IavA+uRaEo=; b=KUahzcpC14Ie48dPcdSQJ6QZtlcsK2320mHAj6uqBSDqQxYllvHTGnzqpZNM+tF41E vkhYrBlULYj8YRvly5p41tb4vQiqyabWHtEQRuaz1xzK0aSovB0z1sWAwzbP/UswMufB 9DYHvjD7RchS/iHI8X8y20wivtlRyJ1wTRzy/cCvUjz8pkyjnPnIGDHNa/OY34+eHBd1 Uf/UB0BHoQBKDFHXbZOhTNgzQuLCoDSFcLm4qBNgZc8OfoilqTDuuKfXS9KLmt7aRzFJ cEMlGiGKLnfDk5zOlWZP1LkRnf30mdXtMV68sRcffFaD5eB2wUFGI6AjEJdES+P7LTeE tF8Q== X-Gm-Message-State: AOAM5330kSYZPZs+EQ13cT4/MfoYrwIvHLJPRMpsA8wKR/FwdM+TkaVY AXP9HKgTfZe+d8XatGytYiM= X-Google-Smtp-Source: ABdhPJxOV2pnvd4lRyD2GaRicxMc4bUuviK0934CFnFBC+0Rw4DJXnDN5ils6SSbqIFnK2IvDJI8XA== X-Received: by 2002:a05:600c:c5:: with SMTP id u5mr17318823wmm.49.1629730283894; Mon, 23 Aug 2021 07:51:23 -0700 (PDT) Received: from nunojsa-N551JK.fritz.box ([2001:a61:2531:cb01:1061:e4b5:709f:d9ad]) by smtp.googlemail.com with ESMTPSA id o8sm15465136wmq.21.2021.08.23.07.51.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Aug 2021 07:51:23 -0700 (PDT) Message-ID: <12d40e96658a005d857a49eccede2ac9620c5e2d.camel@gmail.com> Subject: Re: [PATCH 1/2] iio: ltc2983: add support for optional reset gpio From: Nuno =?ISO-8859-1?Q?S=E1?= To: Andy Shevchenko Cc: Nuno =?ISO-8859-1?Q?S=E1?= , linux-iio@vger.kernel.org, Jonathan Cameron , Lars-Peter Clausen , Drew Fustini Date: Mon, 23 Aug 2021 16:51:22 +0200 In-Reply-To: References: <20210820065535.6994-1-nuno.sa@analog.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Mon, 2021-08-23 at 17:27 +0300, Andy Shevchenko wrote: > On Mon, Aug 23, 2021 at 3:51 PM Nuno Sá > wrote: > > On Mon, 2021-08-23 at 14:14 +0300, Andy Shevchenko wrote: > > > On Fri, Aug 20, 2021 at 9:53 AM Nuno Sá > > > wrote: > > > > Check if an optional reset gpio is present and if so, make sure > > > > to > > > > reset > > > > the device. > > > > > > ... > > > > > > > + usleep_range(1000, 1005); > > > > > > The delta should be at least 20%, otherwise I'm not sure why such > > > a > > > strict range? > > > > > > > No special reason... I just had no hard requirement for delta so I > > just > > gave something small. Is 20% documented anywhere? > > Quick search shows nothing, but I remember I saw it somewhere. > So, the explanation is empirical, because the idea behind is to allow > less HRT interrupts. When you do a tough margin, you may generate too > many interrupts from the timer. So, 20% seems like a good balance for > most of the values. > I see, that makes sense to me. > The parameters to take into account are: > - minimum (or maybe rather median?) CPU frequency the code will be > run on > - minimal sleep (for small sleeps even better to have udelay() as I > believe documented in timers.rst, for bigger sleeps, like 10ms the > margin can be 10% or so) udelay() would be for sleeps < 10us - Nuno Sá