From: Andre Przywara <andre.przywara@arm.com>
To: Samuel Holland <samuel@sholland.org>,
Maxime Ripard <maxime.ripard@bootlin.com>,
Chen-Yu Tsai <wens@csie.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-sunxi@googlegroups.com, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/2] Allwinner A64 timer workaround
Date: Fri, 11 May 2018 10:24:48 +0100 [thread overview]
Message-ID: <9d12075e-745d-b7d7-9847-f1493fc8647e@arm.com> (raw)
In-Reply-To: <20180511022751.9096-1-samuel@sholland.org>
Hi,
On 11/05/18 03:27, Samuel Holland wrote:
> Hello,
>
> Several people (including me) have experienced extremely large system
> clock jumps on their A64-based devices, apparently due to the
> architectural timer going backward, which is interpreted by Linux as
> the timer wrapping around after 2^56 cycles.
So I experienced this before, though I didn't see actual clock jumps,
only that subsequent reads of CNTVCT_EL0, both directly via mrs and
indirectly via CLOCK_MONOTONIC, from userland (triggered by a directed
test) *sometimes* went backwards, with a number of '1's in the lower bits.
But that didn't happen on every boot, and I was suspecting that some
timer setup was missing on the hardware/firmware side. And later on I
failed to reproduce it anymore.
So do you see it on every boot, with recent U-Boot/ATF?
Cheers,
Andre.
> Investigation led to discovery of some obvious problems with this SoC's
> architectural timer, and this patch series introduces what I believe is
> the simplest workaround. More details are in the commit message for
> patch 1. Patch 2 simply enables the workaround in the device tree.
>
> Thanks,
> Samuel
>
> Samuel Holland (2):
> arm64: arch_timer: Workaround for Allwinner A64 timer instability
> arm64: dts: allwinner: a64: Enable A64 timer workaround
>
> arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 1 +
> drivers/clocksource/Kconfig | 11 ++++++++
> drivers/clocksource/arm_arch_timer.c | 39 +++++++++++++++++++++++++++
> 3 files changed, 51 insertions(+)
>
> --
> 2.16.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
next prev parent reply other threads:[~2018-05-11 9:25 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-11 2:27 [PATCH 0/2] Allwinner A64 timer workaround Samuel Holland
2018-05-11 2:27 ` [PATCH 1/2] arm64: arch_timer: Workaround for Allwinner A64 timer instability Samuel Holland
2018-05-11 8:26 ` Maxime Ripard
2018-05-11 8:48 ` Marc Zyngier
2018-05-11 15:08 ` Samuel Holland
2018-05-26 15:15 ` André Przywara
2018-05-11 2:27 ` [PATCH 2/2] arm64: dts: allwinner: a64: Enable A64 timer workaround Samuel Holland
2018-05-11 9:24 ` Andre Przywara [this message]
2018-07-03 15:09 ` [PATCH 0/2] Allwinner " Marc Zyngier
2018-07-03 18:42 ` Samuel Holland
2018-07-04 8:16 ` Marc Zyngier
2018-07-04 8:19 ` Chen-Yu Tsai
2018-07-04 8:23 ` Daniel Lezcano
2018-07-04 8:39 ` Marc Zyngier
2018-07-04 10:00 ` Thomas Gleixner
2018-07-04 13:08 ` [linux-sunxi] " Andre Przywara
2018-07-04 14:31 ` Thomas Gleixner
2018-07-04 14:44 ` Andre Przywara
2018-07-04 15:01 ` Marc Zyngier
2018-07-04 15:15 ` Andre Przywara
2018-07-04 15:30 ` Marc Zyngier
2018-07-04 15:23 ` Samuel Holland
2018-07-04 15:14 ` Thomas Gleixner
2018-07-04 15:43 ` Andre Przywara
2018-07-04 19:49 ` Thomas Gleixner
2018-07-04 8:41 ` Daniel Lezcano
2018-07-12 2:23 ` Samuel Holland
2018-07-04 9:06 ` Maxime Ripard
2018-07-04 8:41 ` Daniel Lezcano
2018-07-04 12:52 ` [linux-sunxi] " Andre Przywara
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