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 B76CBC4338F for ; Mon, 23 Aug 2021 14:28:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AB31613CD for ; Mon, 23 Aug 2021 14:28:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229969AbhHWO2n (ORCPT ); Mon, 23 Aug 2021 10:28:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58256 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229518AbhHWO2n (ORCPT ); Mon, 23 Aug 2021 10:28:43 -0400 Received: from mail-pg1-x52a.google.com (mail-pg1-x52a.google.com [IPv6:2607:f8b0:4864:20::52a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8DBCBC061575 for ; Mon, 23 Aug 2021 07:28:00 -0700 (PDT) Received: by mail-pg1-x52a.google.com with SMTP id n18so16831791pgm.12 for ; Mon, 23 Aug 2021 07:28:00 -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:content-transfer-encoding; bh=bjQEsLqePkSp+fckGJHN1HGW8nuzD9cy9eWdu/7Z29E=; b=sRDDT634cVGLJAeYm3j/a/0wlLwwbYe4vx+2um6llkDYHfXU3Wqp4vsQupJHtPN2A0 /U4bLz7fhfrRxvAH7qPjvKMUfHYqolkFG5mDK8RlbnNBCNXxlfxghc2tfikh7Ipgjgld 7dR76UE/dUXgWuTKAo5blKPIkU/RJD31znfD1kOggmyp01ZdoO+oiuSj39tbjmJL1VQ7 RUJIqxijfEubAOc8ttH2yIE3ZJbgMfD0GTj15xWoFykN9JE7x6kn9l88JUwDTmETGdMo oj67d2O2xEKH7+9Ly1XXUhkHSyMNmT0NU9SZ520jfypXYNucjzt/TgjVzoK02WCS/NQZ x1SA== 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:content-transfer-encoding; bh=bjQEsLqePkSp+fckGJHN1HGW8nuzD9cy9eWdu/7Z29E=; b=rOcOh+4Tl5JieN66tvGKNg9FwKFLjFXC24pPPdzQIakXGeP6gobCOjl19XXRB0HrVq whvAQDTStJ7Wm+D+V/5yjPBlHqVRrVPZvVHnUxTJvA/j7MvvjqxexGZ9xNVELEstp/vb TpBxOjRhvAaejR0AyumMYtXVkhYnNQXgRiaiDi9D16gxbz91IUQ/NY8Tc4wojI387hPa 5NlmsYDOOKPPtVCQC5795JsZ6BCBhzkCTkREAjwKYKDYHh6NBOnYPn90gbAXNv5nVjXF 9ee5QHlhCmuNCBnRRs28kZFmI9elTHq0Ejg4EPR4C4Vk55oQvPlD+ACYBi8O/t1svPn1 fjMw== X-Gm-Message-State: AOAM530O6QH7qDZV3XhDMoSv6LjXaZKALeYpAQMGiL5tdChSllWgDVcx fh3b8CEwyKm0GRykeUburzWqS20rzE4mzTHZ7+A= X-Google-Smtp-Source: ABdhPJwgOXRErPe7n3Sc5+NvZclH8v9tiU/z6PpwWyu9U8sYyey/D+cMUSDnvVZfnNOUolK3F+aSTrABpgIx80Jx9nM= X-Received: by 2002:a05:6a00:d41:b0:3e1:3316:2ef with SMTP id n1-20020a056a000d4100b003e1331602efmr34669902pfv.40.1629728880009; Mon, 23 Aug 2021 07:28:00 -0700 (PDT) MIME-Version: 1.0 References: <20210820065535.6994-1-nuno.sa@analog.com> In-Reply-To: From: Andy Shevchenko Date: Mon, 23 Aug 2021 17:27:20 +0300 Message-ID: Subject: Re: [PATCH 1/2] iio: ltc2983: add support for optional reset gpio To: =?UTF-8?B?TnVubyBTw6E=?= Cc: =?UTF-8?B?TnVubyBTw6E=?= , linux-iio@vger.kernel.org, Jonathan Cameron , Lars-Peter Clausen , Drew Fustini Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Mon, Aug 23, 2021 at 3:51 PM Nuno S=C3=A1 wrote: > On Mon, 2021-08-23 at 14:14 +0300, Andy Shevchenko wrote: > > On Fri, Aug 20, 2021 at 9:53 AM Nuno S=C3=A1 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. 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) - NO_HZ kernel configuration - etc (if anything I forgot) > I did a quick look on > the API's and I could not find nothing related. Anyways, if that is a > best practise for being more power friendly I'm happy to change it... > (well, we might end up just having 100ms here which means 'msleep()'). --=20 With Best Regards, Andy Shevchenko