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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 58DB7C433DF for ; Thu, 21 May 2020 14:22:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D3E1207F7 for ; Thu, 21 May 2020 14:22:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729605AbgEUOWe (ORCPT ); Thu, 21 May 2020 10:22:34 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:38780 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728207AbgEUOW1 (ORCPT ); Thu, 21 May 2020 10:22:27 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 376CF8030776; Thu, 21 May 2020 14:22:22 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8PSENPxDhIuf; Thu, 21 May 2020 17:22:21 +0300 (MSK) Date: Thu, 21 May 2020 17:22:19 +0300 From: Serge Semin To: Geert Uytterhoeven CC: Serge Semin , Thomas Gleixner , Thomas Bogendoerfer , Daniel Lezcano , Alexey Malahov , Paul Burton , Ralf Baechle , Alessandro Zummo , Alexandre Belloni , Arnd Bergmann , Rob Herring , "open list:BROADCOM NVRAM DRIVER" , , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Paul Cercueil , Krzysztof Kozlowski , Geert Uytterhoeven , Randy Dunlap , Claudiu Beznea , Maarten ter Huurne , Vincenzo Frascino , Linux Kernel Mailing List Subject: Re: [PATCH v4 7/7] clocksource: mips-gic-timer: Mark GIC timer as unstable if ref clock changes Message-ID: <20200521142219.ejsl4y5eaqqfsp5k@mobilestation> References: <20200521005321.12129-1-Sergey.Semin@baikalelectronics.ru> <20200521005321.12129-8-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 21, 2020 at 11:09:50AM +0200, Geert Uytterhoeven wrote: > Hi Serge, > > On Thu, May 21, 2020 at 2:54 AM Serge Semin > wrote: > > Currently clocksource framework doesn't support the clocks with variable > > frequency. Since MIPS GIC timer ticks rate might be unstable on some > > platforms, we must make sure that it justifies the clocksource > > requirements. MIPS GIC timer is incremented with the CPU cluster reference > > clocks rate. So in case if CPU frequency changes, the MIPS GIC tick rate > > changes synchronously. Due to this the clocksource subsystem can't rely on > > the timer to measure system clocks anymore. This commit marks the MIPS GIC > > based clocksource as unstable if reference clock (normally it's a CPU > > reference clocks) rate changes. The clocksource will execute a watchdog > > thread, which lowers the MIPS GIC timer rating to zero and fallbacks to a > > new stable one. > > > > Note we don't need to set the CLOCK_SOURCE_MUST_VERIFY flag to the MIPS > > GIC clocksource since normally the timer is stable. The only reason why > > it gets unstable is due to the ref clock rate change, which event we > > detect here in the driver by means of the clocks event notifier. > > > > Signed-off-by: Serge Semin > > Thanks for your patch! > > > --- a/drivers/clocksource/mips-gic-timer.c > > +++ b/drivers/clocksource/mips-gic-timer.c > > @@ -24,6 +24,9 @@ > > static DEFINE_PER_CPU(struct clock_event_device, gic_clockevent_device); > > static int gic_timer_irq; > > static unsigned int gic_frequency; > > +static bool __read_mostly gic_clock_unstable; > > + > > +static void git_clocksource_unstable(char *reason); > > gic_clocksource_unstable? (everywhere) This is the most used word lately. So my hands write git everywhere by itself.) Thanks for noticing this. -Sergey > > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds