> It is racing. For "too much work for irq", here is sequence events
> analyzed by a Motorola engineer:
Thanks - this is enormously helpful in understanding the report.
> 5) The LSR indicates that the transmitter needs data,
> but also indicates the presence of data in the FIFO (0x61 in the LSR)
> 6) The processing function receives the characters, and
> outputs data to the FIFO
> 7) At the exact time (very very small window) that the
> character is read from the FIFO, the FIFO timeout occurs locking in an
> interrupt cause
> 8) The next loop through the interrupt code begins
> 9) The IIR now indicates the data timeout interrupt
> (0xCC in the IIR)
> 10) The processing function is called and it reads the
> LSR
> 11) The LSR is 0 indicating nothing to do
> 12) The interrupt loop continues (the IIR won't clear
> until a character is pulled) until it reaches its max count and
> displays the error.
So we only need to check this in serial8250_handle_irq when IIR indicates
a data timeout interrupt ?
Can we do
if ((iir & 0x0F) == 0x0C) {
/* Expensive RDI check */
}
Alan
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