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.
Mark
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