double power button events on presario 900 - apparently a timing issue?

double power button events on presario 900 - apparently a timing issue?

[Fedor Karpelevitch]

Hi,

as I previously mentioned I am seeing an annoying problem on my 
presario 900 - when power button (works as FF here) is pressed it 
generates two events every time. I was experimentin with debugging 
output and noticed an interesting thing - if I do 
echo 0xffffffff > /proc/acpi/debug_level
to get verbose debug output the problem goes away - I only get one 
event every time button is pressed. Looks like the problem is caused 
by some kind timing issue which goes away when debugging slows it 
down. Does this sound like a reasonable guess? Would anyone suggest 
how this can be debugged further?

Thanks

Fedor


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Re: double power button events on presario 900 - apparently a timing issue?

[Nate Lawson]

On Wed, 24 Sep 2003, Fedor Karpelevitch wrote:
> as I previously mentioned I am seeing an annoying problem on my
> presario 900 - when power button (works as FF here) is pressed it
> generates two events every time. I was experimentin with debugging
> output and noticed an interesting thing - if I do
> echo 0xffffffff > /proc/acpi/debug_level
> to get verbose debug output the problem goes away - I only get one
> event every time button is pressed. Looks like the problem is caused
> by some kind timing issue which goes away when debugging slows it
> down. Does this sound like a reasonable guess? Would anyone suggest
> how this can be debugged further?

It means you need to debounce the event.

-Nate


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Re: double power button events on presario 900 - apparently a timing issue?

[Fedor Karpelevitch]

Nate Lawson wrote:
> On Wed, 24 Sep 2003, Fedor Karpelevitch wrote:
> > as I previously mentioned I am seeing an annoying problem on my
> > presario 900 - when power button (works as FF here) is pressed it
> > generates two events every time. I was experimentin with
> > debugging output and noticed an interesting thing - if I do
> > echo 0xffffffff > /proc/acpi/debug_level
> > to get verbose debug output the problem goes away - I only get
> > one event every time button is pressed. Looks like the problem is
> > caused by some kind timing issue which goes away when debugging
> > slows it down. Does this sound like a reasonable guess? Would
> > anyone suggest how this can be debugged further?
>
> It means you need to debounce the event.

do you mean debouncing on the receiving end? or would that be some way 
to avoid that in the kernel code?

Fedor.


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Re: double power button events on presario 900 - apparently a timing issue?

[Fedor Karpelevitch]

Fedor Karpelevitch wrote:
> Nate Lawson wrote:
> > On Wed, 24 Sep 2003, Fedor Karpelevitch wrote:
> > > as I previously mentioned I am seeing an annoying problem on my
> > > presario 900 - when power button (works as FF here) is pressed
> > > it generates two events every time. I was experimentin with
> > > debugging output and noticed an interesting thing - if I do
> > > echo 0xffffffff > /proc/acpi/debug_level
> > > to get verbose debug output the problem goes away - I only get
> > > one event every time button is pressed. Looks like the problem
> > > is caused by some kind timing issue which goes away when
> > > debugging slows it down. Does this sound like a reasonable
> > > guess? Would anyone suggest how this can be debugged further?
> >
> > It means you need to debounce the event.
>
> do you mean debouncing on the receiving end? or would that be some
> way to avoid that in the kernel code?
>
by the way, I found that it is sufficient to do

echo 0x0800000f > /proc/acpi/debug_level and problem disappears. That 
bit is ACPI_DB_INTERRUPTS which is only referenced it two places...

Fedor.


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Re: double power button events on presario 900 - apparently a timing issue?

[Nate Lawson]

On Thu, 25 Sep 2003, Fedor Karpelevitch wrote:
> Fedor Karpelevitch wrote:
> > Nate Lawson wrote:
> > > On Wed, 24 Sep 2003, Fedor Karpelevitch wrote:
> > > > as I previously mentioned I am seeing an annoying problem on my
> > > > presario 900 - when power button (works as FF here) is pressed
> > > > it generates two events every time. I was experimentin with
> > > > debugging output and noticed an interesting thing - if I do
> > > > echo 0xffffffff > /proc/acpi/debug_level
> > > > to get verbose debug output the problem goes away - I only get
> > > > one event every time button is pressed. Looks like the problem
> > > > is caused by some kind timing issue which goes away when
> > > > debugging slows it down. Does this sound like a reasonable
> > > > guess? Would anyone suggest how this can be debugged further?
> > >
> > > It means you need to debounce the event.
> >
> > do you mean debouncing on the receiving end? or would that be some
> > way to avoid that in the kernel code?
> >
> by the way, I found that it is sufficient to do
>
> echo 0x0800000f > /proc/acpi/debug_level and problem disappears. That
> bit is ACPI_DB_INTERRUPTS which is only referenced it two places...

The kernel should debounce the button events after receiving them from
ACPICA.  Your debugging level change merely increases the latency between
handling events so that the second event is missed.

-Nate


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