Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v2 0/5] arm64: sunxi: Enable the sun4i timer
To:     Samuel Holland <samuel@sholland.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Rob Herring <robh+dt@kernel.org>,
        Maxime Ripard <mripard@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Cc:     devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org
References: <20210322044707.19479-1-samuel@sholland.org>
 <7bb14a82-5dc9-cefe-4b58-1d2c83974965@linaro.org>
 <64f6d712-11fe-4626-aa24-8e31c21a8ad4@sholland.org>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <0b3689ad-6bb3-bd7a-46be-0c4d3d7de268@linaro.org>
Date:   Wed, 24 Mar 2021 10:33:06 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <64f6d712-11fe-4626-aa24-8e31c21a8ad4@sholland.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 24/03/2021 04:51, Samuel Holland wrote:
> 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.

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 <daniel.lezcano@linaro.org>


-- 
<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