From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH] arm64: dts: allwinner: a64: Drop PMU node Date: Wed, 7 Aug 2019 13:56:14 +0200 Message-ID: <20190807115614.phm7sbyae6yajkug@flea> References: <20190806140135.4739-1-anarsoul@gmail.com> <89402d22-d432-9551-e787-c8ede16dbe5f@arm.com> <36e60078-7dd5-9c07-ffa1-6092d8c70fa8@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Vasily Khoruzhick Cc: Mark Rutland , devicetree , "Jared D . McNeill" , Chen-Yu Tsai , Rob Herring , Harald Geyer , Robin Murphy , arm-linux List-Id: devicetree@vger.kernel.org On Tue, Aug 06, 2019 at 07:39:26PM -0700, Vasily Khoruzhick wrote: > On Tue, Aug 6, 2019 at 2:14 PM Robin Murphy wrote: > > > > On 2019-08-06 9:52 pm, Vasily Khoruzhick wrote: > > > On Tue, Aug 6, 2019 at 1:19 PM Harald Geyer wrote: > > >> > > >> Vasily Khoruzhick writes: > > >>> On Tue, Aug 6, 2019 at 7:35 AM Robin Murphy wrote: > > >>>> > > >>>> On 06/08/2019 15:01, Vasily Khoruzhick wrote: > > >>>>> Looks like PMU in A64 is broken, it generates no interrupts at all and > > >>>>> as result 'perf top' shows no events. > > >>>> > > >>>> Does something like 'perf stat sleep 1' at least count cycles correctly? > > >>>> It could well just be that the interrupt numbers are wrong... > > >>> > > >>> Looks like it does, at least result looks plausible: > > >> > > >> I'm using perf stat regularly (cache benchmarks) and it works fine. > > >> > > >> Unfortunately I wasn't aware that perf stat is a poor test for > > >> the interrupts part of the node, when I added it. So I'm not too > > >> surprised I got it wrong. > > >> > > >> However, it would be unfortunate if the node got removed completely, > > >> because perf stat would not work anymore. Maybe we can only remove > > >> the interrupts or just fix them even if the HW doesn't work? > > > > > > I'm not familiar with PMU driver. Is it possible to get it working > > > without interrupts? > > > > Yup - you get a grumpy message from the driver, it will refuse sampling > > events (the ones which weren't working anyway), and if you measure > > anything for long enough that a counter overflows you'll get wonky > > results. But for counting hardware events over relatively short periods > > it'll still do the job. > > I tried to drop interrupts completely from the node but 'perf top' is > still broken. Though now in different way: it complains "cycles: PMU > Hardware doesn't support sampling/overflow-interrupts. Try 'perf > stat'" I have no idea if that's the culprit, but what is the state of the 0x09010000 register? (in particular, are the bits 16-19 and 24 set or not? Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com