From: Vasily Khoruzhick <anarsoul@gmail.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
devicetree <devicetree@vger.kernel.org>,
"Jared D . McNeill" <jmcneill@netbsd.org>,
Maxime Ripard <maxime.ripard@bootlin.com>,
Chen-Yu Tsai <wens@csie.org>, Rob Herring <robh+dt@kernel.org>,
Harald Geyer <harald@ccbib.org>,
arm-linux <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: dts: allwinner: a64: Drop PMU node
Date: Tue, 6 Aug 2019 19:39:26 -0700 [thread overview]
Message-ID: <CA+E=qVeAR4AFN99ZVy8EZLW6p_8ucTewOdMis37wnpV3DObaGg@mail.gmail.com> (raw)
In-Reply-To: <36e60078-7dd5-9c07-ffa1-6092d8c70fa8@arm.com>
On Tue, Aug 6, 2019 at 2:14 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 2019-08-06 9:52 pm, Vasily Khoruzhick wrote:
> > On Tue, Aug 6, 2019 at 1:19 PM Harald Geyer <harald@ccbib.org> wrote:
> >>
> >> Vasily Khoruzhick writes:
> >>> On Tue, Aug 6, 2019 at 7:35 AM Robin Murphy <robin.murphy@arm.com> 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'"
Is there any way to make it working?
>
> Robin.
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next prev parent reply other threads:[~2019-08-07 2:39 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 14:01 [PATCH] arm64: dts: allwinner: a64: Drop PMU node Vasily Khoruzhick
2019-08-06 14:35 ` Robin Murphy
2019-08-06 14:45 ` Vasily Khoruzhick
2019-08-06 20:19 ` Harald Geyer
2019-08-06 20:52 ` Vasily Khoruzhick
2019-08-06 21:14 ` Robin Murphy
2019-08-07 2:39 ` Vasily Khoruzhick [this message]
2019-08-07 11:56 ` Maxime Ripard
2019-08-07 17:36 ` Vasily Khoruzhick
2019-08-08 16:26 ` Maxime Ripard
2019-08-08 19:59 ` Vasily Khoruzhick
2019-08-12 8:04 ` Maxime Ripard
2019-08-12 18:01 ` Vasily Khoruzhick
2019-08-12 18:22 ` Harald Geyer
2019-08-13 5:39 ` Maxime Ripard
2019-09-23 23:51 ` Vasily Khoruzhick
2019-09-23 23:55 ` Vasily Khoruzhick
2019-09-25 11:08 ` Maxime Ripard
2019-10-31 19:10 ` Clément Péron
2019-10-31 20:35 ` Vasily Khoruzhick
2019-11-01 11:30 ` Clément Péron
2019-11-01 15:47 ` Andre Przywara
2019-11-11 1:43 ` André Przywara
2019-08-07 11:59 ` Robin Murphy
2019-08-07 11:12 ` Mark Rutland
2019-08-06 19:10 ` Emmanuel Vadot
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