PPC 85xx serial port error

[Kumar Gala]

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