Re: [PATCH v2 0/5] arm64: sunxi: Enable the sun4i timer
From: Daniel Lezcano <hidden>
Date: 2021-03-24 09:34:04
Also in:
linux-devicetree, linux-sunxi, lkml
On 24/03/2021 04:51, Samuel Holland wrote:
On 3/22/21 9:18 AM, Daniel Lezcano wrote:quoted
On 22/03/2021 05:47, Samuel Holland wrote:quoted
In preparation for adding CPU idle states, hook up the sun4i timer. Having a non-c3stop clockevent source available is necessary for all CPUs to simultaneously enter a local-timer-stop idle state.Why simultaneously ?Because the CPU providing (the hrtimer providing) the broadcast timer cannot enter an idle state which would stop that timer. So in my case, with 4 CPUs, I was seeing at most 3 CPUs enter idle at any given time. This prevented any cluster-level idle states from doing anything. After applying this series, I was able to observe the whole cluster powering down when appropriate.
Ah, ok. I did not realize this fourth CPU was acting as the broadcast timer, so allowing at least a CPU power down. This setup is unusual. The changes make sense. Acked-by: Daniel Lezcano <redacted> -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel