> On 8/21/2020 4:43 PM, Limonciello, Mario wrote: > >> -----Original Message----- From: Mark Pearson > >> <markpearson@xxxxxxxxxx> Sent: Friday, August 21, 2020 15:06 > >> > >> On 8/21/2020 4:00 PM, Limonciello, Mario wrote: <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. > >>> > >> The problem is I don't have a good way to disable the firmware > >> (that I know of yet) so a modprobe parameter wouldn't really do > >> much. I guess it could skip providing the sysfs entry points - but > >> the FW will still be there doing it's thing, so I'm not sure I see > >> the benefit of that. At least the sysfs entry point gives a bit > >> more insight into what is going on. Let me know if I'm missing > >> something obvious. > >> > > > > Oh so it's not actually the driver loading tells the firmware it's > > supposed to work this way. The firmware actually detects "I'm > > running on Linux, so I'll do this differently"? > > > Right. This patch is just providing a more friendly interface so user > space can see what is going on and be able to do control of the > different modes without the need for hotkeys. > > Afraid I don't have much insight into the nitty gritty details of > exactly how that works - I believe it's related to detecting the use of > DPTF but the details aren't shared with me because of NDA's. As a > thought it's quite possible (probable?) that if thermald is using DPTF > the firmware will automatically disable itself. Proving that might be > tricky - I'll see if the firmware team have any ideas. > Right - it's a reverse engineered implementation done in thermald and there are still some missing items. So your comment makes perfect sense to me now, and if/when those other things are added this may change and it will make sense to offer a way to turn this off at that time.
