Hi all, year(s) ago it was discovered that MCT timer and ARM architectured timer are the same hardware with different interface. Here [1]. I followed mail-list discussions about removing MCT and using arch timer for Exynos5-based SoCs but things aren't moving at least latest upstream kernel on odroid-xu3 will use MCT as default timers. Maybe the reason are some power-management related things that very specific to Samsung. I don't know. Idea of this draft patchset comes from Doug patches when he tried to optimize read of 64-bit counter located in mmio. [2] Why not using cp15 counter instead if possible? Previous numbers for 1000000 gettimeofday() calls from userspace are about 1 ms. With this patches we have 0.5 ms or even better. So twice as fast. Just as matter of interest i tried to perform 2000000 sched_yield() calls from userspace. I see around 20% speedup with patches applied. I tried to use hackbench but it's hard to feel the difference, maybe speedup is 0.5% but with bad fluctuation. Everything is tested on odroid-xu3. Looks like Cortex-A9 based Samsung SoCs (odroid-u2, odroid-x) don't have arch timer. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014 -May/256943.html [2] https://lkml.org/lkml/2014/6/20/431 Current code created with such assumptions: -- don't want to insert huge refactoring in MCT code; -- target platform only ARMv7 Exynos5-based SoC that works in 32-bit mode so i don't want to build described functionality on ARM64. Currently i'm trying to patch odroid-xu3 DT only. -- firmware on odroid-xu3 is broken and secondary cores start in SVC mode instead of HYP mode. Maybe i can remove check for hyp mode; -- in addition instead of DT property I may parse PFR regs and find Generic Timer Extension there. I hope you are not getting bored reading to me. Current code is a little bit draft so comments and ideas are welcome. Best regards, Alexey Klimov -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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