IRQ problem in multifunction PCMCIA card

kaustav.majumdar at kaustav.majumdar at
Tue Jun 20 05:31:02 EDT 2006

I have a true multifunction PCMCIA card with UART function as function 0
and USB function as function 1.
The USB is OHCI compliant and UART is 16950 standard.

We are facing a problem of irq handling when both of the functions are
running simultaneously.

The serial function is using the serial_cs and 8250 as its drivers.
The USB function has its own custom driver.
These two functions are running perfectly in isolation.

But if we start bulk transfer by copying a large file (12MB say) to a
USB Disk connected to the USB port of the PC card, and at the same time
we start sending a continuous stream of characters through the serial
port (I am using minicom with serial loop back and continuously pressing
a key), after sometime both copying and character printing in the
minicom window stops.

On further investigation I had seen interrupts for the USB port comes
continuously even after the copying had stopped but the TX holding reg
empty and Rx Data ready interrupts are not coming to the serial port
when it had stopped printing characters in the minicom.

Also I had noted that with the same bulk transfer if I type in the
minicom window in a slow manner (say 10 characters/ min) then both of
them are functioning well.

I had also checked that my CONFIG_SERIAL_8250_SHARE_IRQ is selected as

Can anyone pl suggest what may be the issue?


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