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SubjectRe: [PATCH v3 0/2] Allwinner A64 timer workaround
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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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