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-ker...@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
