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([2a01:e34:ed2f:f020:91e2:6a05:a4ac:7d0a]) by smtp.googlemail.com with ESMTPSA id n4sm1595499wmq.40.2021.03.24.02.33.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Mar 2021 02:33:07 -0700 (PDT) Subject: Re: [PATCH v2 0/5] arm64: sunxi: Enable the sun4i timer To: Samuel Holland , Thomas Gleixner , Rob Herring , Maxime Ripard , Chen-Yu Tsai , Jernej Skrabec , Catalin Marinas , Will Deacon 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 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog