Mystery clicking under keyboard, 3.x only, SSD only

Mystery clicking under keyboard, 3.x only, SSD only

[Bill Gribble]

I am running Debian Sid on a Viliv N5, which is an Atom Z520/Poulsbo
(GMA500) UMPC.  It has no rotating media or fans. With Debian's
linux-image-2.6.39-2-686-pae and earlier kernels behavior is normal
(except for flaky libertas wifi, which is why I seek to upgrade). 

Any 3.0 or 3.1 kernel I have tried from Debian (I have tried each
incremental version, most recently linux-image-3.1.0-1-686-pae) starts,
within a minute after boot, to make a soft clicking noise from under
the keyboard.  Clicks appear to be correlated with
interrupt-generating activity such as moving a mouse pointer or
pressing keys.  This clicking does not start in earnest until an X
server comes up, but even booting into single-user mode I hear it
some.  With an X display up, there is a continuous stream of 5-10
clicks per second, more when moving the mouse pointer.

There is no disk or fan on this machine (SSD only).  The audio system
is Intel HDA; I have tried muting all mixer channels, turning all
volumes to 0, even blacklisting all the intel HDA modules and all the
pc speaker modules.  In any case, the speaker for the device is in the
screen bezel, not the keyboard (I think; I have never gotten the
speaker to work properly).  

I have also tried blacklisting the psb_gfx module in 3.1.  

I see nothing of interest in any logs.  Nothing I have done changes the
behavior at all.

Any thoughts about what this could be?  I am getting a little crazy
about it.  

Thanks,
Bill Gribble

 

Re: Mystery clicking under keyboard, 3.x only, SSD only

[Alexander E. Patrakov]

12.12.2011 01:24, Bill Gribble wrote:
> I am running Debian Sid on a Viliv N5, which is an Atom Z520/Poulsbo
> (GMA500) UMPC.  It has no rotating media or fans. With Debian's
> linux-image-2.6.39-2-686-pae and earlier kernels behavior is normal
> (except for flaky libertas wifi, which is why I seek to upgrade).
>
> Any 3.0 or 3.1 kernel I have tried from Debian (I have tried each
> incremental version, most recently linux-image-3.1.0-1-686-pae) starts,
> within a minute after boot, to make a soft clicking noise from under
> the keyboard.  Clicks appear to be correlated with
> interrupt-generating activity such as moving a mouse pointer or
> pressing keys.  This clicking does not start in earnest until an X
> server comes up, but even booting into single-user mode I hear it
> some.  With an X display up, there is a continuous stream of 5-10
> clicks per second, more when moving the mouse pointer.
>
> There is no disk or fan on this machine (SSD only).  The audio system
> is Intel HDA; I have tried muting all mixer channels, turning all
> volumes to 0, even blacklisting all the intel HDA modules and all the
> pc speaker modules.  In any case, the speaker for the device is in the
> screen bezel, not the keyboard (I think; I have never gotten the
> speaker to work properly).

This clicking can be related to the events when the device goes to deep 
powersaving levels. Fluctuations in the consumed current can lead to 
audible clicks due to bad screening of audio wires, loose ferrite cores 
in the coils, magnetostriction effect, etc.

You can test this theory by running several copies of "yes > /dev/null" 
and thus eating 100% CPU. If this eliminates the clicking effect, then 
my guess is correct and you have to disable some of the deepest 
powersaving states to remove the clicks.

-- 
Alexander E. Patrakov

Re: Mystery clicking under keyboard, 3.x only, SSD only

[Bill Gribble]

On Mon, 2011-12-12 at 23:10 +0600, Alexander E. Patrakov wrote:
> This clicking can be related to the events when the device goes to deep 
> powersaving levels. Fluctuations in the consumed current can lead to 
> audible clicks due to bad screening of audio wires, loose ferrite cores 
> in the coils, magnetostriction effect, etc.
> 
> You can test this theory by running several copies of "yes > /dev/null" 
> and thus eating 100% CPU. If this eliminates the clicking effect, then 
> my guess is correct and you have to disable some of the deepest 
> powersaving states to remove the clicks.

Got it in one!  Causing 100% CPU utilization does indeed stop the
clicking.  I will look for power saving settings that I can control. 

Thanks,
Bill Gribble