Messages in this thread | | | From | "Zhang, Rui" <> | Subject | RE: [PATCH v3 3/4] thermal/core: Build ascending ordered indexes for the trip points | Date | Fri, 22 Jul 2022 07:15:56 +0000 |
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> -----Original Message----- > From: Daniel Lezcano <daniel.lezcano@linaro.org> > Sent: Thursday, July 21, 2022 5:35 PM > To: Zhang, Rui <rui.zhang@intel.com>; rafael@kernel.org > Cc: quic_manafm@quicinc.com; amitk@kernel.org; lukasz.luba@arm.com; > linux-pm@vger.kernel.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH v3 3/4] thermal/core: Build ascending ordered indexes > for the trip points > Importance: High > > On 19/07/2022 16:17, Zhang Rui wrote: > > On Tue, 2022-07-19 at 09:22 +0200, Daniel Lezcano wrote: > >> On 19/07/2022 03:14, Zhang Rui wrote: > >>> On Mon, 2022-07-18 at 15:21 +0200, Daniel Lezcano wrote: > >>>> > >>>> Hi Zhang, > >>>> > >>>> thanks for the review > >>>> > >>>> On 18/07/2022 07:28, Zhang Rui wrote: > >>>>> On Fri, 2022-07-15 at 23:09 +0200, Daniel Lezcano wrote: > >>>> > >>>> [ ... ] > >>>> > >>>>>> Instead of taking the risk of breaking the existing platforms, > >>>>>> use an array of temperature ordered trip identifiers and make it > >>>>>> available for the code needing to browse the trip points in an > >>>>>> ordered way. > >>>>>> > >>>>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> > >>>>>> --- > >>>> > >>>> [ ... ] > >>>> > >>>>>> +static void sort_trips_indexes(struct thermal_zone_device > >>>>>> *tz) > >>>>>> +{ > >>>>>> + int i, j; > >>>>>> + > >>>>>> + for (i = 0; i < tz->trips; i++) > >>>>>> + tz->trips_indexes[i] = i; > >>>>>> + > >>>>>> + for (i = 0; i < tz->trips; i++) { > >>>>>> + for (j = i + 1; j < tz->trips; j++) { > >>>>>> + int t1, t2; > >>>>>> + > >>>>>> + tz->ops->get_trip_temp(tz, tz- > >>>>>>> trips_indexes[i], &t1); > >>>>> > >>>>> This line can be moved to the upper loop. > >>>> > >>>> Right, thanks! > >>>> > >>>>>> + tz->ops->get_trip_temp(tz, tz- > >>>>>>> trips_indexes[j], &t2); > >>>>>> + > >>>>> > >>>>> what about the disabled trip points? > >>>>> > >>>>> we should ignore those trip points and check the return value to > >>>>> make sure we're comparing the valid trip_temp values. > >>>> > >>>> We don't have to care about, whatever the position, the > >>>> corresponding trip id will be disabled by the trip init function > >>>> before calling this one and ignored in the handle_thermal_trip() > >>>> function > >>> > >>> hah, I missed this one and replied to your latest reply directly. > >>> > >>> The thing I'm concerning is that if we don't check the return value, > >>> for a disabled trip point, the trip_temp (t1/t2) returned is some > >>> random value, it all depends on the previous value set by last > >>> successful .get_trip_temp(), and this may screw up the sorting. > >> > >> The indexes array is the same size as the trip array, that makes the > >> code much less prone to errors. > >> > >> To have the same number of trip points, the index of the disabled > >> trip must be inserted also in the array. We don't care about its > >> position in the indexes array because it is discarded in the > >> handle_trip_point() function anyway. For this reason, the random > >> temperature of the disabled trip point and the resulting position in > >> the sorting is harmless. > >> > >> It is made on purpose to ignore the return value, so we have a > >> simpler code. > >> > > Let's take below case for example, > > say, we have three trip points 0, 1, 2, and trip point 1 is broken and > > disabled. > > > > trip temp for trip point 0 is 10 and for trip point 2 is 20. > > .get_trip_temp(tz, 1, &t) fails, and t is an uninitialized random > > value > > > > > > Initial: > > trip_indexes[0]=0,trip_indexes[1]=1,trip_indexes[2]=2 > > step1: > > i=0,j=1 > > get trip temp for trip point trip_indexes[0]=0 and trip_indexes[1]=1 > > trip point 1 returns trip temp 5, and it swaps with trip point 0 > > so > > trip_indexes[0]=1,trip_indexes[1]=0,trip_indexes[2]=2 > > step2: > > i=0,j=2 > > get trip temp for trip point trip_indexes[0]=1 and trip_indexes[2]=2 > > trip point 1 returns trip temp 25, and it swaps with trip point 2 > > so > > trip_indexes[0]=2,trip_indexes[1]=0,trip_indexes[2]=1 > > > > And the sorting is broken now. > > > > please correct me if I'm missing anything. > > Oh, nice! Thanks for the detailed explanation. > > We can initialize t1 and t2 to INT_MAX, so if the get_trip_temp() fails, they > will be set to the maximum temperature and it will be at the end of the array. > > Alternatively, we check the disabled bit and set the temperature to INT_MAX.
IMO, we can 1. get the trip temp for each trip point and cache them 2. set the trips_disabled bit 3. do the sorting using the cached trip temp values in thermal_zone_device_trip_init() altogether.
Thanks, rui > > > > > > -- > <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
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