linux-kernel - Re: [PATCH v3 0/2] Allwinner A64 timer workaround

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Message-ID: <9738319a-4154-62be-2325-2873dfb326dc@linaro.org>
Date:   Mon, 14 Jan 2019 13:56:55 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Samuel Holland <samuel@...lland.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <Mark.Rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v3 0/2] Allwinner A64 timer workaround

On 13/01/2019 03:17, Samuel Holland wrote:
> This is the third version of a patch series to fix system clock jumps
> and other timer instability on the Allwinner A64 SoC. It has now been
> tested for a week, and I've received no reports of date jumps with this
> version. So this is, as far as I can tell, a complete workaround.
> 
> See the commit messages for a detailed description of the issue, but the
> summary is that, when a high counter bit rolls over, indeterminance in
> the low bits causes CNTPCT/CNTVCT and their respective TVAL registers to
> jump forward or backward. Backward jumps (or the next read after forward
> jumps) are sometimes seen by the kernel and interpreted as the timer
> wrapping around after 2^56 cycles. This causes the system clock to jump
> forward approximately 91 years.
> 
> changes since v2;
> - Reduced workaround threshold from 11 to 10 bits based on reports from
>   other hardare and the U-Boot version of this workaround
> - Added TVAL handling based on Marc's suggestion
> - Added erratum documentation and renamed symbols to match
> - Added Maxime's Acked-by
> 
> changes since v1:
> - Add an iteration limit like most other arch timer workarounds
> - Added Andre's Tested-by
> 
> Samuel Holland (2):
>   arm64: arch_timer: Workaround for Allwinner A64 timer instability
>   arm64: dts: allwinner: a64: Enable A64 timer workaround
> 
>  Documentation/arm64/silicon-errata.txt        |  2 +
>  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi |  1 +
>  drivers/clocksource/Kconfig                   | 10 ++++
>  drivers/clocksource/arm_arch_timer.c          | 55 +++++++++++++++++++
>  4 files changed, 68 insertions(+)
> 

Applied. Took the opportunity to add the stable@ tag.

Thanks

  -- Daniel


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