System hang on athlon64 cpufreq change

System hang on athlon64 cpufreq change

[wixor]

Hello all,
I'm not sure if this problem belongs here, I have no other idea where
to post however.

My kernel boots up with performance cpufreq governor, thus setting
frequency to 2hgz. Then I change it to powersave governor, thus
setting frequency to 1ghz just like that:

echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

Everything works well. Then I launch mplayer and in 1/4 - 1/5 cases
system hangs (I mean nothing works, including numlock and sysrq key).
I suspect it's something with video card driver, and here comes my
problem. I use ati's proprietary fglrx driver (i guess they may be
calibrating they own delay loop, or something, and cputfreq change
ruins it), so kernel is tainted, so you are unable to track the
problem down.... eh.... well, but i hope there is some tiny chance
there is something wrong i do, or maybe cpu doesn't like so drastic
freq changes... well, if anybody has some idea, or just experience
like mine, I ask for help. Thanks in advance.

root: ~: cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 47
model name      : AMD Athlon(tm) 64 Processor 3200+
stepping        : 2
cpu MHz         : 1000.000
cache size      : 512 KB
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext
fxsr_opt lm 3dnowext 3dnow pni lahf_lm
bogomips        : 2010.88
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc

RE: System hang on athlon64 cpufreq change

[Langsdorf, Mark]

> My kernel boots up with performance cpufreq governor, thus setting
> frequency to 2hgz. Then I change it to powersave governor, thus
> setting frequency to 1ghz just like that:
> 
> echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> 
> Everything works well. Then I launch mplayer and in 1/4 - 1/5 cases
> system hangs (I mean nothing works, including numlock and sysrq key).
> I suspect it's something with video card driver, and here comes my
> problem. I use ati's proprietary fglrx driver (i guess they may be
> calibrating they own delay loop, or something, and cputfreq change
> ruins it), so kernel is tainted, so you are unable to track the
> problem down.... eh.... well, but i hope there is some tiny chance
> there is something wrong i do, or maybe cpu doesn't like so drastic
> freq changes... well, if anybody has some idea, or just experience
> like mine, I ask for help. Thanks in advance.

The processor is not changing frequency in response to your
launch of mplayer.  The powersave governor forces it to the
lowest frequency regardless of system load.  You really want
to use ondemand for dynamic frequency scaling.

Can you use a serial or network console to capture any messages
the kernel is sending when mplayer starts?

-Mark Langsdorf
AMD, Inc.

Re: System hang on athlon64 cpufreq change

[wixor]

On 3/16/07, Langsdorf, Mark <mark.langsdorf@amd.com> wrote:
> The processor is not changing frequency in response to your
> launch of mplayer.  The powersave governor forces it to the
> lowest frequency regardless of system load.  You really want
> to use ondemand for dynamic frequency scaling.
>
> Can you use a serial or network console to capture any messages
> the kernel is sending when mplayer starts?
>
Well, that's the point - i fix cpu speed at 1ghz and everything works
UNTIL I launch mplayer. I've just reproduced this (set governor,
launched mplayer and waited 15-20 mins) and the whole system seems
frozen - just like before. Network is down (no responses to ping). How
to redirect dmesg to serial port? (I'm running 2.6.19 kernel and
8.34.8 fglrx driver.)

Thanks and sorry for 2week delay... (btw - now it is you [ati] who is
responsible for both my cpu and gpu drivers, yes? :D)

RE: System hang on athlon64 cpufreq change

[Langsdorf, Mark]

 
> On 3/16/07, Langsdorf, Mark <mark.langsdorf@amd.com> wrote:
> > The processor is not changing frequency in response to your
> > launch of mplayer.  The powersave governor forces it to the
> > lowest frequency regardless of system load.  You really want
> > to use ondemand for dynamic frequency scaling.
> >
> > Can you use a serial or network console to capture any messages
> > the kernel is sending when mplayer starts?
> >
> Well, that's the point - i fix cpu speed at 1ghz and everything works
> UNTIL I launch mplayer. I've just reproduced this (set governor,
> launched mplayer and waited 15-20 mins) and the whole system seems
> frozen - just like before. Network is down (no responses to ping). How
> to redirect dmesg to serial port? (I'm running 2.6.19 kernel and
> 8.34.8 fglrx driver.)

My point is that is there is no cpufreq change when you
start mplayer with the powersave governor.  Have you 
disabled powernow! entirely (by removing the module) and
demonstrated that mplayer works on your machine at all?

To redirect the console, add console=ttyS0,115200 to your 
kernel command line and run a serial console from the serial 
port on the test machine to another machine, and then use your 
preferred serial port capture program (minicom or whatever) 
to capture the text.
 
> Thanks and sorry for 2week delay... (btw - now it is you [ati] who is
> responsible for both my cpu and gpu drivers, yes? :D)

AMD bought ATI, not the other way around.  That said, elements
of AMD are responsible for the PowerNow! driver, and other 
elements of AMD are responsible for the fglrx driver.

-Mark Langsdorf
Operating Systems Research Center
AMD, Inc.