Re: [PATCH v8 7/8] thermal: Add PCIe cooling driver

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On Thu, Oct 17, 2024 at 2:16 PM Ilpo Järvinen
<ilpo.jarvinen@xxxxxxxxxxxxxxx> wrote:
>
> On Thu, 17 Oct 2024, Jonathan Cameron wrote:
>
> > On Wed,  9 Oct 2024 12:52:22 +0300
> > Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> wrote:
> >
> > > Add a thermal cooling driver to provide path to access PCIe bandwidth
> > > controller using the usual thermal interfaces.
> > >
> > > A cooling device is instantiated for controllable PCIe Ports from the
> > > bwctrl service driver.
> > >
> > > If registering the cooling device fails, allow bwctrl's probe to
> > > succeed regardless. As cdev in that case contains IS_ERR() pseudo
> > > "pointer", clean that up inside the probe function so the remove side
> > > doesn't need to suddenly make an odd looking IS_ERR() check.
> > >
> > > The thermal side state 0 means no throttling, i.e., maximum supported
> > > PCIe Link Speed.
> > >
> > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > > Acked-by: Rafael J. Wysocki <rafael@xxxxxxxxxx> # From the cooling device interface perspective
> >
> > Trivial thing noticed on a reread.
> >
> >
> > > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> > > index 61e7ae524b1f..d3f9686e26e7 100644
> > > --- a/drivers/thermal/Kconfig
> > > +++ b/drivers/thermal/Kconfig
> > > @@ -220,6 +220,15 @@ config DEVFREQ_THERMAL
> > >
> > >       If you want this support, you should say Y here.
> > >
> > > +config PCIE_THERMAL
> > > +   bool "PCIe cooling support"
> > > +   depends on PCIEPORTBUS
> > > +   help
> > > +     This implements PCIe cooling mechanism through bandwidth reduction
> > > +     for PCIe devices.
> >
> > Technically links not devices, but don't think that matters much
>
> That distinction would be splitting hairs beyond what seems useful from
> ordinary user's point of view. If there's no device attached, BW
> controller cannot do anything since the link is not going to train.
> The link speed reduction is going to impact the speed the device
> can communicate with even if it technically occurs on the link.


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