Re: [PATCH v3 00/14] thermal: Rework binding cooling devices to trip points

[Nícolas F. R. A. Prado]

On Mon, Aug 26, 2024 at 11:58:12AM +0200, Rafael J. Wysocki wrote:
> On Sat, Aug 24, 2024 at 8:45 PM Nícolas F. R. A. Prado
> <nfraprado@xxxxxxxxxxxxx> wrote:
> >
> > On Mon, Aug 19, 2024 at 05:49:07PM +0200, Rafael J. Wysocki wrote:
> > > Hi Everyone,
> > >
> > > This is one more update of
> > >
> > > https://lore.kernel.org/linux-pm/3134863.CbtlEUcBR6@xxxxxxxxxxxxx/#r
> > >
> > > the cover letter of which was sent separately by mistake:
> > >
> > > https://lore.kernel.org/linux-pm/CAJZ5v0jo5vh2uD5t4GqBnN0qukMBG_ty33PB=NiEqigqxzBcsw@xxxxxxxxxxxxxx/
> > >
> > > and it has been updated once already:
> > >
> > > https://lore.kernel.org/linux-pm/114901234.nniJfEyVGO@xxxxxxxxxxxxx/
> > >
> > > Relative to the v2 above it drops 3 patches, one because it was broken ([04/17
> > > in the v2), and two more that would need to be rebased significantly, either
> > > because of dropping the other broken patch or because of the recent Bang-bang
> > > governor fixes:
> > >
> > > https://lore.kernel.org/linux-pm/1903691.tdWV9SEqCh@xxxxxxxxxxxxx/
> > >
> > > The remaining 14 patches, 2 of which have been slightly rebased and the rest
> > > is mostly unchanged (except for some very minor subject and changelog fixes),
> > > is not expected to be controversial and are targeting 6.12, on top of the
> > > current linux-next material.
> > >
> > > The original motivation for this series quoted below has not changed:
> > >
> > >  The code for binding cooling devices to trip points (and unbinding them from
> > >  trip point) is one of the murkiest pieces of the thermal subsystem.  It is
> > >  convoluted, bloated with unnecessary code doing questionable things, and it
> > >  works backwards.
> > >
> > >  The idea is to bind cooling devices to trip points in accordance with some
> > >  information known to the thermal zone owner (thermal driver).  This information
> > >  is not known to the thermal core when the thermal zone is registered, so the
> > >  driver needs to be involved, but instead of just asking the driver whether
> > >  or not the given cooling device should be bound to a given trip point, the
> > >  thermal core expects the driver to carry out all of the binding process
> > >  including calling functions specifically provided by the core for this
> > >  purpose which is cumbersome and counter-intuitive.
> > >
> > >  Because the driver has no information regarding the representation of the trip
> > >  points at the core level, it is forced to walk them (and it has to avoid some
> > >  locking traps while doing this), or it needs to make questionable assumptions
> > >  regarding the ordering of the trips in the core.  There are drivers doing both
> > >  these things.
> > >
> > > The first 5 patches in the series are preliminary.
> > >
> > > Patch [06/14] introduces a new .should_bind() callback for thermal zones and
> > > patches [07,09-12/14] modifies drivers to use it instead of the .bind() and
> > > .unbind() callbacks which allows them to be simplified quite a bit.
> > >
> > > The other patches [08,13-14/14] get rid of code that becomes unused after the
> > > previous changes and do some cleanups on top of that.
> > >
> > > The entire series along with 2 patches on top of it (that were present in the
> > > v2 of this set of patches) is available in the thermal-core-testing git branch:
> > >
> > > https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/log/?h=thermal-core-testing
> > >
> > > (note that this branch is going to be rebased shortly on top of 6.11-rc4
> > > and the thermal control material in linux-next).
> > >
> > > Thanks!
> >
> > Hi,
> >
> > KernelCI has identified a boot regression originating from this series. I've
> > verified that reverting the series fixes the issue.
> 
> Thanks for the report!
> 
> There was a bug in the original patch [12/14] that would cause
> symptoms like what you are observing to appear, which was reported on
> Friday and has since been fixed in the tree.  Please see:
> 
> https://lore.kernel.org/linux-pm/CAJZ5v0iw7uXE_cfU5VXOjFDg9GM8Hu0+hKxqfzU3v0OM5KK9oQ@xxxxxxxxxxxxxx/
> 
> You probably have not tested the fixed tree yet, so please let
> kernelci run again on it and if the issue is still there, please let
> me know.

Indeed it has been fixed.

#regzbot fix: 'thermal/of: Use the .should_bind() thermal zone callback'

Thanks,
Nícolas