Re: after resume from suspend to disk, x86_64 CPU frequency throttling stops working - a known issue ?

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

On 03/11/2012 01:54 AM, Jason Vas Dias wrote:

> Hi - since many kernel versions ago (I believe 2.6.38+), now running
> 3.1.1 (built from 'stable' GIT tree),
> CPU frequency throttling once the maximum fans have been enabled does
> not work after I resume
> my HP 6715b x86_64 2.2GHz TL64 dual-core laptop from disk . The trip
> point temperatures are :
> $ cat /sys/class/thermal/thermal_zone0/trip_point_*temp | tr '\n' ' '
> 105000 95000 75000 65000 50000 15900
> 
> When the 95-degree thermal_zone0 trip point is exceeded, the CPU is
> meant to be throttled back from 2.2Ghz to 800Khz, until the
> temperature
> falls below the trip point when the normal frequency is restored (with
> some hystereisis delay factor) .
> 
> On boot-up from a 'pm-hibernate' suspend-to-disk on my laptop ,
> however,  the 95-degree trip point is triggered,  but no CPU frequency
> throttling occurs, and no  below-95-degree
> trip-point is triggerred, so the CPU eventually reaches the 105 degree
> trip-point and does an emergency power-off if it is heavily loaded.
> Also, the system
> in this state generates only one 95 degree trip-point event ;  after
> the temperature falls below 95-degrees for some time (over 10mins) ,
> and then I load
> the machine again, so the temperature again exceeds 95-degrees, no
> ACPI thermal event is raised .
> 
> This occurs with ANY available "governor" - I use "ondemand" by
> default, with a 'scaling_max_freq' set to 2.0Ghz (because when I run
> the CPU at 2.2Ghz , and load the machine
> (with for instance  a large package 'make -j2' build) I get hardware
> 'system hang' issues - I've tried every available means to get the
> kernel to trace / log something or boot a crash
> kernel when this occurs, with no luck, so have concluded this is a
> hardware issue - it did not occur when the laptop was new (it is now
> nearly 4 years old) - since the machine  goes
> into a state that is totally unresponsive to anything (mouse,
> keyboard, networking, video,  serial, parport, USB devices all hang),
> only a PCI bus analyzer will help solve this).
> But I've reproduced the no-throttling-
> above-95-degrees-after-suspend-from-disk problem with EVERY governor:
> performance, userspace, etc.  I have the powernow-k8 CPU
>  frequency scaling module built-in to the kernel.
> 
> I've resorted to hacking together an acpid driven thermal.sh shell
> script that, on receipt of a 95 degree event, spawns a daemon process
> that periodically monitors
> the thermal_zone0 temperature and if the temp is above 95 and the freq
> is above 800Khz, sets the frequency down a notch, and back to where it
> was
> when the temperature falls below 95 degrees.
> 
> Is this a known kernel issue ? Should I raise a bug about this ? I can
> post detailed logs showing the events occurring and CPU frequency
> throttling when booted up from cold,
> and no frequency scaling and only one 95-degree event when booted from
> suspend to disk - I wanted to check if this was a known issue first (a
> bugzilla search for
> 'no ACPI thermal event after resume from disk' returned zarro boogs).
> 
> Comments and advice would be much appreciated,
> 


Just a wild guess, but does the patch posted below help?
https://lkml.org/lkml/2012/2/28/288

(It applies on current Linux mainline.)
 
Regards,
Srivatsa S. Bhat
IBM Linux Technology Center