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Date: Wed, 20 May 2020 09:58:18 +0530 From: Amit Kucheria <amit.kucheria@...durent.com> To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, LKML <linux-kernel@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org> Subject: Re: [RFC][PATCH 3/5] thermal: Add support for setting notification thresholds On Tue, May 19, 2020 at 5:10 AM Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> wrote: > > On Mon, 2020-05-18 at 18:37 +0200, Daniel Lezcano wrote: > > On 04/05/2020 20:16, Srinivas Pandruvada wrote: > > > Add new attributes in thermal syfs when a thermal drivers provides > > > callbacks for them and CONFIG_THERMAL_USER_EVENT_INTERFACE is > > > defined. > > > > > > These attribute allow user space to stop polling for temperature. > > > > > > These attributes are: > > > - temp_thres_low: Specify a notification temperature for a low > > > temperature threshold event. > > > temp_thres_high: Specify a notification temperature for a high > > > temperature threshold event. > > > temp_thres_hyst: Specify a change in temperature to send > > > notification > > > again. > > > > > > This is implemented by adding additional sysfs attribute group. The > > > changes in this patch are trivial to add new attributes in thermal > > > sysfs as done for other attributes. > > > > Isn't it duplicate with the trip point? > A trip point is where an in-kernel governor takes some action. This is > not same as a notification temperature. For example at trip point > configured by ACPI at 85C, the thermal governor may start aggressive > throttling. > But a user space can set a notification threshold at 80C and start some > active controls like activate some fan to reduce the impact of passive > control on performance. Then what is the use of thermal trip type "ACTIVE" ? > We need a way to distinguish between temperature notification threshold > and actual trip point. Changing a trip point means that user wants > kernel to throttle at temperature.
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