linux-kernel - Re: [PATCH v2 0/5] arm64: sunxi: Enable the sun4i timer

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Date:   Tue, 23 Mar 2021 22:51:00 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/5] arm64: sunxi: Enable the sun4i timer

On 3/22/21 9:18 AM, Daniel Lezcano wrote:
> On 22/03/2021 05:47, Samuel Holland wrote:
>> 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.

Regards,
Samuel

>> Changes from v1:
>>   - Removed H616 changes (depends on an unmerged patch set)
>>   - Reworded the patch 4-5 commit messages for clarity
>>   - Added Acked-by tags
>>
>> Samuel Holland (5):
>>   dt-bindings: timer: Simplify conditional expressions
>>   dt-bindings: timer: Add compatibles for sun50i timers
>>   arm64: dts: allwinner: a64: Sort watchdog node
>>   arm64: dts: allwinner: Add sun4i MMIO timer nodes
>>   arm64: sunxi: Build the sun4i timer driver
>>
>>  .../timer/allwinner,sun4i-a10-timer.yaml      | 42 +++++++++----------
>>  arch/arm64/Kconfig.platforms                  |  1 +
>>  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 25 +++++++----
>>  arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi  |  9 ++++
>>  4 files changed, 46 insertions(+), 31 deletions(-)
>>
> 
>