From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH] arm64: dts: allwinner: a64: Drop PMU node Date: Thu, 8 Aug 2019 18:26:28 +0200 Message-ID: <20190808162628.pthvy3tgf3naj76s@flea> References: <20190806140135.4739-1-anarsoul@gmail.com> <89402d22-d432-9551-e787-c8ede16dbe5f@arm.com> <36e60078-7dd5-9c07-ffa1-6092d8c70fa8@arm.com> <20190807115614.phm7sbyae6yajkug@flea> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3460593965069158548==" Return-path: 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 --===============3460593965069158548== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="v2jptlbwy23oihws" Content-Disposition: inline --v2jptlbwy23oihws Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Aug 07, 2019 at 10:36:08AM -0700, Vasily Khoruzhick wrote: > On Wed, Aug 7, 2019 at 4:56 AM Maxime Ripard wrote: > > > > 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? > > What register is that and how do I check it? It's in the CPUX Configuration block, and the bits are labelled as CPU Debug Reset. And if you have busybox, you can use devmem. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com --v2jptlbwy23oihws Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCXUxNNAAKCRDj7w1vZxhR xStDAP98jP1Kcn6msHdImj48XPiZcHTbCuRrjrwRFlwdpheW4wEA/tNBydnrBBHr UrB0GkeJjnGzoAR2JgDF28i300VyiQc= =4dGP -----END PGP SIGNATURE----- --v2jptlbwy23oihws-- --===============3460593965069158548== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============3460593965069158548==--