From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754059AbeC1Pbi (ORCPT ); Wed, 28 Mar 2018 11:31:38 -0400 Received: from mail.bootlin.com ([62.4.15.54]:38425 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753691AbeC1Pbh (ORCPT ); Wed, 28 Mar 2018 11:31:37 -0400 Date: Wed, 28 Mar 2018 17:31:35 +0200 From: Alexandre Belloni To: Daniel Lezcano Cc: Alexander Dahl , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Boris Brezillon , Thomas Gleixner Subject: Re: [PATCH v3 0/6] clocksource: rework Atmel TCB timer driver Message-ID: <20180328153135.GG13942@piout.net> References: <20180223171558.7037-1-alexandre.belloni@bootlin.com> <9761072.pX2B0LJlSJ@ada> <989df8a3-462a-c645-87f1-9f956e1b22c9@linaro.org> <4073350.0MmxRoANOi@ada> <6d43177a-bbea-6a01-5fa5-1c7891e18412@linaro.org> <20180328141645.GF13942@piout.net> <75e5917b-a9ba-c67e-e964-3f002681f9bb@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <75e5917b-a9ba-c67e-e964-3f002681f9bb@linaro.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/03/2018 at 16:36:34 +0200, Daniel Lezcano wrote: > On 28/03/2018 16:16, Alexandre Belloni wrote: > > On 28/03/2018 at 15:03:11 +0200, Daniel Lezcano wrote: > >> On 28/03/2018 12:29, Alexander Dahl wrote: > >>> Hello Daniel, > >>> > >>> Am Dienstag, 27. März 2018, 13:30:22 CEST schrieb Daniel Lezcano: > >>>> Can you can give a rough amount for the irq rate on the timer ? > >>> > >>> I used itop [1] now to get a rough estimate. First with kernel v4.14.29-rt25 > >>> (fully preempt RT): > >>> > >>> INT NAME RATE MAX > >>> 19 [ vel tc_clkevt] 397 Ints/s (max: 432) > >>> 26 [ vel eth0] 4 Ints/s (max: 38) > >>> > >>> Next test with kernel v4.15.13 gives (slightly slower, but non-RT): > >>> > >>> INT NAME RATE MAX > >>> 19 [ vel tc_clkevt] 248 Ints/s (max: 273) > >>> 26 [ vel eth0] 4 Ints/s (max: 11) > >>> > >>> With kernel v4.16-rc7 plus this patch series and tcb as clocksource: > >>> > >>> INT NAME RATE MAX > >>> 17 [vel timer@fffa] 2164 Ints/s (max: 2183) > >>> 26 [ vel eth0] 5 Ints/s (max: 10) > >>> > >>> Is this the information you wanted? If not, could you point me on how to get > >>> the requested irq rate? > >> > >> It is perfect. Thanks! > >> > >> It confirms what I was worried about: the clocksource wraps up too > >> quickly thus raising an interrupt every 400us. That is why I asked > >> Alexande about a prescalar register. > >> > > > > The code should behave exactly the same between the previous and the new > > driver. The interrupt is not coming from the clocksource but from the > > clockevent and it is already on the slowest clock, the 32kHz one. > > Do you have an explanation of why the rate is much higher ? > The core is giving deltas of 31 clocks instead of much more than that, I guess I messed up the initialization somewhere. -- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com