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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7949AC433E1 for ; Thu, 11 Jun 2020 08:40:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5674C20656 for ; Thu, 11 Jun 2020 08:40:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726977AbgFKIkV (ORCPT ); Thu, 11 Jun 2020 04:40:21 -0400 Received: from foss.arm.com ([217.140.110.172]:48278 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726956AbgFKIkU (ORCPT ); Thu, 11 Jun 2020 04:40:20 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 143F21FB; Thu, 11 Jun 2020 01:40:20 -0700 (PDT) Received: from bogus (unknown [10.37.12.97]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5BA483F73D; Thu, 11 Jun 2020 01:40:17 -0700 (PDT) Date: Thu, 11 Jun 2020 09:40:14 +0100 From: Sudeep Holla To: Jassi Brar Cc: linux-arm-kernel , Linux Kernel Mailing List , Viresh Kumar , Rob Herring , Frank Rowand , Bjorn Andersson , Vincent Guittot , "arnd@arndb.de" , Sudeep Holla , Jassi Brar Subject: Re: [PATCH] firmware: arm_scmi: fix timeout value for send_message Message-ID: <20200611084014.GB7357@bogus> References: <20200607193023.52344-1-jassisinghbrar@gmail.com> <20200610082315.GB2689@bogus> <20200610155629.GA7357@bogus> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 10, 2020 at 09:45:55PM -0500, Jassi Brar wrote: > On Wed, Jun 10, 2020 at 10:56 AM Sudeep Holla wrote: > > [I admit you can write bigger posts than me, so I am not going to > write a passionate response to each of your paragraphs. > Let's keep it to the point.] > > > > > > if (xfer->hdr.poll_completion) { > > > > > - ktime_t stop = ktime_add_ns(ktime_get(), SCMI_MAX_POLL_TO_NS); > > > > > + ktime_t stop = ktime_add_ns(ktime_get(), 500 * 1000 * NSEC_PER_USEC); > > > > > > > > > > > > > This is unacceptable delay for schedutil fast_switch. So no for this one. > > > > > > > Increasing timeout does not increase latency. > > > > Agreed, but worst case you may be stuck here for 500ms which is not > > acceptable. > > > Not acceptable to who, you or the kernel? :) Now that you said you > are fixing the scmi's fast_switch implementation. > Sorry, I meant to disable it for single channel implementation. I am not saying we want that on Juno/MHU. > Even though I don't think 500ms would ruin our lives, but ok, I will > make it 30ms - same as you did in the 'else' block. And drop the other > change. I am fine if cpufreq maintainers allow that in the fast switch path that happens in the fast path. -- Regards, Sudeep