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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DDF0C433F5 for ; Mon, 7 Mar 2022 23:59:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242797AbiCHAAl (ORCPT ); Mon, 7 Mar 2022 19:00:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33256 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233796AbiCHAAg (ORCPT ); Mon, 7 Mar 2022 19:00:36 -0500 Received: from mail-oo1-xc31.google.com (mail-oo1-xc31.google.com [IPv6:2607:f8b0:4864:20::c31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A908E33E10 for ; Mon, 7 Mar 2022 15:59:39 -0800 (PST) Received: by mail-oo1-xc31.google.com with SMTP id s203-20020a4a3bd4000000b003191c2dcbe8so19977007oos.9 for ; Mon, 07 Mar 2022 15:59:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=KEKG+0hooW1zM7qhTU6cSghfN5cLCif35DDe+3mMJLQ=; b=qFLO6hAIpl06N4GNLGqecP/zlZwavKJvd+C2rXjxnNQPO4w64M+806hqjlD7t5TC6g BNcZsQmoORx6UJxpnwD9nzyJsEPGkmb0zpT0utUZNkmvIvTQPsNqjE/ItkaeHXwNtLfY efsTbuorX+m2WMmD3Euhws5BSxUNtK+/decBRrARGms/jFqz8lQbCru/seLE4bzH+M9f D9u3UAjiDwhUSEja4sQILVR7zt0gV81PgQ7xKfOLlmw9jXZIVArFCZHhQ1up67wWc9fZ 2Jf8M3tT8faHc4vRoIoMP8KxFQi8dtC4xe0MCaKN1gJY+MWmOar9FEoBxNxjw6Fq0f3r 8CfA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=KEKG+0hooW1zM7qhTU6cSghfN5cLCif35DDe+3mMJLQ=; b=jOxhCKwCOnPuxr3IuE6gXpHedlTzmpDNWohASDdjNJVjm5IV7nwMz64S/0eKQ7yRA3 E6ZqjvG/YDOvu/YhR+JXDclMcg40OyoEU7XHbsOYwtnBHLYw6IxTRccFIUtuI8QVtuUS kAAV7srg8m2GqmGdssXyQhAbjScZlqBeDzL4rpW+Be0yJoAi5kcoF5xYDVF9FyaSgSUd NcjQdcpCeGkJ/YCTyjzd1CpAcByrUuXzKJqKoIh3hhZ14qlMdff/UowbN1MAKfsTI9hX bQLuJNswnhNhzQjFbF0AEGU4KfUujrlO8TKto+WDRHwGLdKnIqKLGG+FhgzeKsTbOoFd kAxA== X-Gm-Message-State: AOAM530R5uHQ4YchGpWHUpudh4uLQWrSp0YAnUqI7wZ0gjm5xEAMX01N NJtBO3i49P08FcQVuUsRF7oq5g== X-Google-Smtp-Source: ABdhPJytmm6mXDFw5YmoLtk0zA0zRvReKCgSL+J2N0/BnKQabYOOJvsgpbE9CnKc9Mj8U2BLGCcYMA== X-Received: by 2002:a05:6870:a189:b0:da:b3f:2b83 with SMTP id a9-20020a056870a18900b000da0b3f2b83mr870514oaf.290.1646697578856; Mon, 07 Mar 2022 15:59:38 -0800 (PST) Received: from ripper ([2600:1700:a0:3dc8:205:1bff:fec0:b9b3]) by smtp.gmail.com with ESMTPSA id l4-20020a4a94c4000000b002ea822fbac8sm6381033ooi.21.2022.03.07.15.59.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Mar 2022 15:59:38 -0800 (PST) Date: Mon, 7 Mar 2022 16:01:22 -0800 From: Bjorn Andersson To: Andy Shevchenko Cc: Rob Herring , Daniel Scally , Heikki Krogerus , Sakari Ailus , "Rafael J. Wysocki" , Hans de Goede , linux-usb@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, Dmitry Baryshkov Subject: Re: [PATCH v4 7/7] usb: typec: mux: Add On Semi fsa4480 driver Message-ID: References: <20220307034040.1111107-1-bjorn.andersson@linaro.org> <20220307034040.1111107-7-bjorn.andersson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 07 Mar 14:13 PST 2022, Andy Shevchenko wrote: > On Mon, Mar 07, 2022 at 01:04:50PM -0800, Bjorn Andersson wrote: > > On Mon 07 Mar 08:13 PST 2022, Andy Shevchenko wrote: > > > On Mon, Mar 07, 2022 at 06:48:25AM -0800, Bjorn Andersson wrote: > > > > On Mon 07 Mar 02:16 PST 2022, Andy Shevchenko wrote: > > > > > On Sun, Mar 06, 2022 at 07:40:40PM -0800, Bjorn Andersson wrote: > > ... > > > > > > > + /* 15us to allow the SBU switch to turn off */ > > > > > > + usleep_range(15, 1000); > > > > > > > > > > This is quite unusual range. > > > > > > > > > > If you are fine with the long delay, why to stress the system on it? > > > > > Otherwise the use of 1000 is unclear. > > > > > > > > > > That said, I would expect one of the below: > > > > > > > > > > usleep_range(15, 30); > > > > > usleep_range(500, 1000); > > > > > > > > Glad you asked about that, as you say the typical form is to keep the > > > > range within 2x of the lower value, or perhaps lower + 5. > > > > > > > > But if the purpose is to specify a minimum time and then give a max to > > > > give the system some flexibility in it's decision of when to wake up. > > > > And in situations such as this, we're talking about someone connecting a > > > > cable, so we're in "no rush" and I picked the completely arbitrary 1ms > > > > as the max. > > > > > > > > Do you see any drawback of this much higher number? (Other than it > > > > looking "wrong") > > > > > > I see the drawback of low number. > > > > 15us is based on the data sheet and if the kernel is ready to serve us > > after 15us then let's do that. > > > > > The 1000 makes not much sense to me with the minimum 66x times less. > > > If there is no rush, use some reasonable values, > > > what about > > > > > > usleep_range(100, 1000); > > > > > > ? 10x is way better than 66x. > > > > I don't agree, and in particular putting 100 here because it's 1/10 of > > the number I just made up doesn't sounds like a good reason. The > > datasheet says 15us, so that is at least based on something real. > > > > In https://www.kernel.org/doc/Documentation/timers/timers-howto.txt > > I find the following: > > > > With the introduction of a range, the scheduler is > > free to coalesce your wakeup with any other wakeup > > that may have happened for other reasons, or at the > > worst case, fire an interrupt for your upper bound. > > > > The larger a range you supply, the greater a chance > > that you will not trigger an interrupt; this should > > be balanced with what is an acceptable upper bound on > > delay / performance for your specific code path. Exact > > tolerances here are very situation specific, thus it > > is left to the caller to determine a reasonable range. > > > > Which to me says that the wider range is perfectly reasonable. In > > particular 15, 30 (which seems to be quite common) makes the available > > range to the scheduler unnecessarily narrow. > > > > And it's clear that whatever the upper bound it's going to be some > > arbitrary number, but 1ms should ensure that there are other hrtimer > > interrupts to piggy back on. > > Okay, I have grepped for usleep_range(x[x], yyyy) and there are 9 modules > use it. A few commit messages call 1000 as "reasonable upper limit". > Right, we usually see a much more narrow range, as you say 2x or perhaps 10x, and this why I said I was glad you asked. I have been wondering about this in a few different cases... Thanks, Bjorn