Junk characters in the serial console when Beagle is idle

[GS Menon]

Hello,

I have a REV C4 board with Angstrom Linux (2.6.32) running on it.
Whenever CPU is idle (or when no traffic on Serial line) for a few
seconds, it automatically sends junk characters, and then recovers
back.

This is even worst before login. It would not recover from sending
junk characters on the console. It keeps sending the rogue/junk
characters. I believe some CPU idle demon is thresholding with an idle
time, but I dont understand why should it bother the serial line. I
can recover from this only if I hard-reboot the beagle.

Is there a way to solve the problem. Atleast, is there a way to
increase the idle time threshold. It would save a lot of time for me.

Regards,
GS

[Petr Štetiar]

GS Menon <hifro...@gmail.com> [2010-09-22 03:08:55]:

> Hello,

Hi,

> I have a REV C4 board with Angstrom Linux (2.6.32) running on it.
> Whenever CPU is idle (or when no traffic on Serial line) for a few
> seconds, it automatically sends junk characters, and then recovers
> back.

I think, that what you're seeing might be "feature" of cpuidle enabled in
kernel.

-- ynezz

[Jeff Osier-Mixon]

I have also seen this when CPUIDLE is enabled on rev C boards, due to voltage on the UART floating when the CPU isn't keeping an eye on it.  (At least that's how I understood it when someone smart explained it.)

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[GS Menon]

Hi,

Is there a way to either switch-off CPUIDLE or increase its threshold-
time for CPUIDLE? This would be of great help.

Regards
GS.

On Sep 24, 9:48 am, Jeff Osier-Mixon <je...@jefro.net> wrote:
> I have also seen this when CPUIDLE is enabled on rev C boards, due to
> voltage on the UART floating when the CPU isn't keeping an eye on it.  (At
> least that's how I understood it when someone smart explained it.)
>
> On Thu, Sep 23, 2010 at 12:21 PM, Petr Štetiar <yn...@true.cz> wrote:

> > GS Menon <hifromg...@gmail.com> [2010-09-22 03:08:55]:

>
> > > Hello,
>
> > Hi,
>
> > > I have a REV C4 board with Angstrom Linux (2.6.32) running on it.
> > > Whenever CPU is idle (or when no traffic on Serial line) for a few
> > > seconds, it automatically sends junk characters, and then recovers
> > > back.
>
> > I think, that what you're seeing might be "feature" of cpuidle enabled in
> > kernel.
>
> > -- ynezz
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "Beagle Board" group.
> > To post to this group, send email to beagl...@googlegroups.com.
> > To unsubscribe from this group, send email to

> > beagleboard...@googlegroups.com<beagleboard%2Bunsu...@googlegroups.com>
> > .

[Søren Steen Christensen]

Hi GS,

> Is there a way to either switch-off CPUIDLE or increase its threshold-
> time for CPUIDLE? This would be of great help.

Please have a look at: http://elinux.org/OMAP_Power_Management#UART_wakeup_and_timeout_options, which I think and hope will help :-)

Best regards
Søren

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