PPC 85xx serial port error

We are using an 8541 processor with ELDK 4.0 and 2.6.15 kernel.

Frequently, if we dump large amounts of output to the console port (for=
 example, if we use 'tar' with the verbose option), we see an error message=
 that starts and scrolls until we reboot the unit:
    serial8250: too much work for irq90

We see this at 9600 baud and also at 115200 baud, although it seems to=
 happen less often at 115k.

This message comes from serial8250_interrupt, which appears to trigger it=
 if the interrupt handler has looped 256 times through the list?

How is this possible?  If the interrupt routine is running, does that not=
 prevent user threads from running and adding more data to the list?  Or am=
 I not understanding this code correctly?

Any light that anyone can shed on the expected behavior of this driver and=
 any ideas on how to work around this are greatly appreciated!

Best regards,

Dan.

On Feb 1, 2007, at 4:08 PM, Dan Wilson wrote:

We are using an 8541 processor with ELDK 4.0 and 2.6.15 kernel.

Frequently, if we dump large amounts of output to the console port  
(for example, if we use 'tar' with the verbose option), we see an  
error message that starts and scrolls until we reboot the unit:
    serial8250: too much work for irq90

We see this at 9600 baud and also at 115200 baud, although it seems  
to happen less often at 115k.

This message comes from serial8250_interrupt, which appears to  
trigger it if the interrupt handler has looped 256 times through  
the list?

How is this possible?  If the interrupt routine is running, does  
that not prevent user threads from running and adding more data to  
the list?  Or am I not understanding this code correctly?

Any light that anyone can shed on the expected behavior of this  
driver and any ideas on how to work around this are greatly  
appreciated!

This question may be better addressed by the linux-kernel mailing  
list since its more about how the serial driver works than anything  
PPC specific.

- k