Commit fff21fac authored Jan 30, 2016 by Maciej W. Rozycki Committed by Greg Kroah-Hartman Feb 06, 2016

serial: zs: Fix a transmit lockup in console output

Transmit interrupts are disabled and the transmit buffer drained in the
course of console output so that polled transmission is possible. That
however causes a lost transmit interrupt as the TxIP bit in RR3 is only
set on a transmit buffer full-to-empty transition and then iff transmit
interrupts are enabled at the same time. Consequently if console output
disturbs a regular transmission in progress, the TxIP bit is never set
again and the transmission locks up waiting for a transmit interrupt.

Fix the problem by restarting transmission manually rather than waiting
for a transmit interrupt that will never happen.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent bdc5f300

drivers/tty/serial/zs.c

+4 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1181,6 +1181,10 @@ static void zs_console_write(struct console co, const char s,
	if (txint & TxINT_ENAB) {		if (txint & TxINT_ENAB) {
	zport->regs[1] \|= TxINT_ENAB;		zport->regs[1] \|= TxINT_ENAB;
	write_zsreg(zport, R1, zport->regs[1]);		write_zsreg(zport, R1, zport->regs[1]);

			/* Resume any transmission as the TxIP bit won't be set. */
			if (!zport->tx_stopped)
			zs_raw_transmit_chars(zport);
	}		}
	spin_unlock_irqrestore(&scc->zlock, flags);		spin_unlock_irqrestore(&scc->zlock, flags);
	}		}