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From: Mark P. <mar...@le...> - 2020-08-22 01:32:04
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On 8/21/2020 4:43 PM, Limonciello, Mario wrote: >> -----Original Message----- From: Mark Pearson >> <mar...@le...> 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. Mark |
