linux-kernel - Re: [PATCH v3 3/4] thermal/core: Build ascending ordered indexes for the trip points

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Message-ID: <70468d71603329d781f18380f0271699744c876f.camel@intel.com>
Date:   Tue, 19 Jul 2022 09:35:21 +0800
From:   Zhang Rui <rui.zhang@...el.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>, rafael@...nel.org
Cc:     quic_manafm@...cinc.com, amitk@...nel.org, lukasz.luba@....com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] thermal/core: Build ascending ordered indexes
 for the trip points

On Tue, 2022-07-19 at 09:14 +0800, 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@...aro.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(),

or uninitialized value from the stack, but still random value every
time we invoke .get_trip_temp() for the same trip point.

-rui

>  and this may screw up the sorting.
> 
> thanks,
> rui
> > 
> > 
>