Re: [External] RE: [PATCH v2] platform/x86: thinkpad_acpi: performance mode interface

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> -----Original Message-----
> From: platform-driver-x86-owner@xxxxxxxxxxxxxxx <platform-driver-x86-
> owner@xxxxxxxxxxxxxxx> On Behalf Of Mark Pearson
> Sent: Friday, August 21, 2020 14:36
> To: Limonciello, Mario
> Cc: ibm-acpi-devel@xxxxxxxxxxxxxxxxxxxxx; platform-driver-x86@xxxxxxxxxxxxxxx;
> ibm-acpi@xxxxxxxxxx; bnocera@xxxxxxxxxx; Nitin Joshi
> Subject: Re: [External] RE: [PATCH v2] platform/x86: thinkpad_acpi:
> performance mode interface
> 
> 
> [EXTERNAL EMAIL]
> 
> Hi Mario
> 
> On 8/21/2020 3:15 PM, Limonciello, Mario wrote:
> >>
> <snip>
> >
> > Thanks for adapting a lot of my feedback, this looks much better to me.
> >
> No problems and genuinely thank you for the feedback. Sorry it took so
> long to get this update out - PTO and other things got in the way :)
> 
> >>
> <snip>
> >> +
> >> +The sysfs entry provides the ability to return the current status and to
> set
> >> the
> >> +desired mode. For example::
> >> +
> >> +        echo H > /sys/devices/platform/thinkpad_acpi/dytc_perfmode
> >> +        echo M > /sys/devices/platform/thinkpad_acpi/dytc_perfmode
> >> +        echo L > /sys/devices/platform/thinkpad_acpi/dytc_perfmode
> >> +
> >
> > I was thinking about this some more, do you actually want another mode that
> "disables"
> > this feature?   IE "O" turns it off an calls DYTC_DISABLE_CQL.
> >
> > For example if a user wanted to test the recently landed code in thermald
> 2.3
> > and compare performance between the two it seems like this and that "might"
> fight.
> > As an outsider looking in - I of course may be wrong too here.
> >
> > If at some point in the future thermald does a better job than this
> implementation you
> > might also want an "out" to let thermald or another piece of userland turn
> this off
> > if it's in the picture.
> >
> I'm still digging into this one. Right now I haven't found a good clean
> way of just disabling the firmware. Currently when thermald goes in and
> tweaks the CPU power registers it has the effect of overriding the FW
> anyway - but I appreciate that's not quite the same as actually doing it
> explicitly.
> 

What about a modprobe parameter to disable at least?  That would at least
make it pretty easy to make a change, reboot and compare with thermald (or
other software) without disabling the rest of the functionality of the
thinkpad_acpi driver.

> I'm still discussing with the BIOS team how to implement this - these
> conversations take time.... I suspect I'll need a new BIOS API which
> will take a while to implement and get rolled out. I didn't want to hold
> up this patch as there are benefits for users in the meantime and Lenovo
> do plan on supporting the thermal software going forwards. I'm not not
> dropping the plan to have a disable function as I can see the benefits.
> 


Yup, well aware how these types of things go.

> Thanks for the input. Let me know if you want a reviewed-by tag added. I
> think it's kinda awesome having input from a Dell engineer on a Lenovo
> related driver and I hope in the future I can provide the same help ;)
> Open source is awesome.
> 
> Mark

😊

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