>>>>> "Michal" == Michal Simek <monstr@xxxxxxxxx> writes:
Hi,
Michal> I looked at that loop and I think that we should reread actual
Michal> status before ulite_transmit because status reg can be changed
Michal> when ulite_receive is executed. What do you think? (BTW: status
Michal> reading can be moved directly to ulite_receive/transmit
Michal> functions)
Michal> do {
Michal> int stat = ioread32be(port->membase + ULITE_STATUS);
Michal> busy = ulite_receive(port, stat);
Michal> stat = ioread32be(port->membase + ULITE_STATUS); // check
Michal> status again
Michal> busy |= ulite_transmit(port, stat);
Michal> n++;
Michal> } while (busy);
It shouldn't really matter - ulite_transmit() only looks at TXFULL, and
in the unlikely case where it was full but 1 character got transmitted
during ulite_receive, we will catch it during the 2nd iteration of the
loop (as busy will be true).
The logic was afaik more-or-less directly copied from 8250.c
Michal> 1. Before fault happen:
Michal> ISR is called, status is 0x18 (interrupt enabled, tx fifo full) just
Michal> to ulite_transmit and detect TXFULL and return to ISR. Head and tail
Michal> are correct
Michal> 2. Broken part
Michal> ISR is called, status is 0x14 (interrupt enabled, tx fifo empty), jump
Michal> to ulite_transmit. Here I am printing (head and tail values are
Michal> zero). Xmit buffer address is the same. Then uart_circ_empty(xmit)
Michal> detects that head and tail are the same which means nothing to print.
Michal> My question: Is there any part of the code which can change xmit head
Michal> and tail values?
Yes, ulite_transmit does (for tail). head is only changed by the serial core.
Michal> BTW: Getty is providing that login prompt. Could it be an issue with getty?
Maybe. Or the fact that it calls set_termios or similar. Are you unable
to reproduce the problem with other programs?
--
Bye, Peter Korsgaard
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