From: Daniel Lezcano <daniel.lezcano@linaro.org> To: Martin Kepplinger <martin.kepplinger@puri.sm>, viresh.kumar@linaro.org, kevin.wangtao@linaro.org, leo.yan@linaro.org, edubezval@gmail.com, vincent.guittot@linaro.org, javi.merino@kernel.org, rui.zhang@intel.com, daniel.thompson@linaro.org Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver Date: Mon, 5 Aug 2019 09:37:43 +0200 [thread overview] Message-ID: <2d7f1caa-351a-8fdc-bb6b-151f7313a042@linaro.org> (raw) In-Reply-To: <20190805051111.24318-1-martin.kepplinger@puri.sm> On 05/08/2019 07:11, Martin Kepplinger wrote: > --- [ ... ] >> +static s64 cpuidle_cooling_runtime(struct cpuidle_cooling_device *idle_cdev) >> +{ >> + s64 next_wakeup; >> + unsigned long state = idle_cdev->state; >> + >> + /* >> + * The function should not be called when there is no >> + * mitigation because: >> + * - that does not make sense >> + * - we end up with a division by zero >> + */ >> + if (!state) >> + return 0; >> + >> + next_wakeup = (s64)((idle_cdev->idle_cycle * 100) / state) - >> + idle_cdev->idle_cycle; >> + >> + return next_wakeup * NSEC_PER_USEC; >> +} >> + > > There is a bug in your calculation formula here when "state" becomes 100. > You return 0 for the injection rate, which is the same as "rate" being 0, > which is dangerous. You stop cooling when it's most necessary :) Right, thanks for spotting this. > I'm not sure how much sense really being 100% idle makes, so I, when testing > this, just say if (state == 100) { state = 99 }. Anyways, just don't return 0. > > Daniel, thanks a lot for these additions! Could you send an update of this? Yes, I'm working on a new version. > btw, that's what I'm referring to: > https://lore.kernel.org/linux-pm/1522945005-7165-1-git-send-email-daniel.lezcano@linaro.org/ > I know it's a little old already, but it seems like there hasn't been any > equivalent solution in the meantime, has it? > > Using cpuidle for cooling is way more effective than cpufreq (which often > hardly is). On which platform that happens? -- <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
next prev parent reply other threads:[~2019-08-05 7:37 UTC|newest] Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-05 16:16 [PATCH v3 0/7] CPU cooling device new strategies Daniel Lezcano 2018-04-05 16:16 ` [PATCH v3 1/7] thermal/drivers/cpu_cooling: Fixup the header and copyright Daniel Lezcano [not found] ` <20180411061514.GL7671@vireshk-i7> 2018-04-11 8:56 ` Daniel Lezcano 2018-04-05 16:16 ` [PATCH v3 2/7] thermal/drivers/cpu_cooling: Add Software Package Data Exchange (SPDX) Daniel Lezcano 2018-04-05 16:16 ` [PATCH v3 3/7] thermal/drivers/cpu_cooling: Remove pointless field Daniel Lezcano 2018-04-05 16:16 ` [PATCH v3 4/7] thermal/drivers/Kconfig: Convert the CPU cooling device to a choice Daniel Lezcano [not found] ` <20180411061851.GM7671@vireshk-i7> 2018-04-11 8:58 ` Daniel Lezcano 2018-04-05 16:16 ` [PATCH v3 5/7] thermal/drivers/cpu_cooling: Add idle cooling device documentation Daniel Lezcano 2018-04-05 16:16 ` [PATCH v3 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver Daniel Lezcano 2018-04-11 8:51 ` Viresh Kumar 2018-04-11 9:29 ` Daniel Lezcano 2018-04-13 11:23 ` Sudeep Holla 2018-04-13 11:47 ` Daniel Lezcano 2018-04-16 7:37 ` Viresh Kumar 2018-04-16 7:44 ` Daniel Lezcano 2018-04-16 9:34 ` Sudeep Holla 2018-04-16 9:37 ` Viresh Kumar 2018-04-16 9:45 ` Daniel Lezcano 2018-04-16 9:50 ` Viresh Kumar 2018-04-16 10:03 ` Daniel Lezcano 2018-04-16 10:10 ` Viresh Kumar 2018-04-16 12:10 ` Daniel Lezcano 2018-04-16 12:30 ` Lorenzo Pieralisi 2018-04-16 13:57 ` Daniel Lezcano 2018-04-16 14:22 ` Lorenzo Pieralisi 2018-04-17 7:17 ` Daniel Lezcano 2018-04-17 10:24 ` Lorenzo Pieralisi 2018-04-16 12:31 ` Sudeep Holla 2018-04-16 12:49 ` Daniel Lezcano 2018-04-16 13:03 ` Sudeep Holla 2018-04-16 12:29 ` Sudeep Holla 2018-04-13 11:38 ` Daniel Thompson 2018-04-13 11:46 ` Daniel Lezcano 2019-08-05 5:11 ` Martin Kepplinger 2019-08-05 6:53 ` Martin Kepplinger 2019-08-05 7:39 ` Daniel Lezcano 2019-08-05 7:42 ` Martin Kepplinger 2019-08-05 7:58 ` Daniel Lezcano 2019-10-25 11:22 ` Martin Kepplinger 2019-10-25 14:45 ` Daniel Lezcano 2019-10-26 18:23 ` Martin Kepplinger 2019-10-28 15:16 ` Daniel Lezcano 2019-08-05 7:37 ` Daniel Lezcano [this message] 2019-08-05 7:40 ` Martin Kepplinger 2018-04-05 16:16 ` [PATCH v3 7/7] cpuidle/drivers/cpuidle-arm: Register the cooling device Daniel Lezcano 2018-04-11 8:51 ` Viresh Kumar
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