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[94.29.10.250]) by smtp.googlemail.com with ESMTPSA id q26sm5372252lfo.65.2019.11.03.07.25.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 03 Nov 2019 07:25:20 -0800 (PST) Subject: Re: [PATCH v7 17/19] PM / devfreq: tegra30: Support variable polling interval From: Dmitry Osipenko To: =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Cc: Thierry Reding , MyungJoo Ham , Kyungmin Park , Chanwoo Choi , Jonathan Hunter , Tomeu Vizoso , Peter Geis , linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20191029220019.26773-1-digetx@gmail.com> <20191029220019.26773-18-digetx@gmail.com> <20191101215816.GB8724@qmqm.qmqm.pl> <590f47a4-c75a-e8c9-88b8-b3cd98578969@gmail.com> Message-ID: <71a16d74-5908-ea97-ae98-4b7d0e99a765@gmail.com> Date: Sun, 3 Nov 2019 18:25:19 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <590f47a4-c75a-e8c9-88b8-b3cd98578969@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org 02.11.2019 01:23, Dmitry Osipenko пишет: > 02.11.2019 00:58, Michał Mirosław пишет: >> On Wed, Oct 30, 2019 at 01:00:17AM +0300, Dmitry Osipenko wrote: >>> The ACTMON governor is interrupt-driven and currently hardware's polling >>> interval is fixed to 16ms in the driver. Devfreq supports variable polling >>> interval by the generic governors, let's re-use the generic interface for >>> changing of the polling interval. Now the polling interval can be changed >>> dynamically via /sys/class/devfreq/devfreq0/polling_interval. >> [...] >>> @@ -308,7 +308,7 @@ static unsigned long actmon_device_target_freq(struct tegra_devfreq *tegra, >>> unsigned int avg_sustain_coef; >>> unsigned long target_freq; >>> >>> - target_freq = dev->avg_count / ACTMON_SAMPLING_PERIOD; >>> + target_freq = dev->avg_count / tegra->devfreq->profile->polling_ms; >>> avg_sustain_coef = 100 * 100 / dev->config->boost_up_threshold; >>> target_freq = do_percent(target_freq, avg_sustain_coef); >>> target_freq += dev->boost_freq; >> >> Noting a comment in patch 13, if this is hot path you could try reciprocal_divide(). > > Hello Michał, > > This not really a hot path, I just wanted to optimize that case to keep > things a bit nicer. > > Please take a look at the arch/arm/boot/compressed/lib1funcs.S, firstly > it checks whether divisor is a power of 2 value and then takes optimized > code path that uses a single shift. Hence the patch 13 still applies here. On the other hand, there is now only a single case of the division by polling_ms in the driver which won't bring much benefit, so it indeed makes sense to skip the patch 13 for now.