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pmac_zilog: Fix unexpected irq
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On most 68k Macs the SCC IRQ is an autovector interrupt and cannot be
masked. This can be a problem when pmac_zilog starts up.

For example, the serial debugging code in arch/m68k/kernel/head.S may be
used beforehand. It disables the SCC interrupts at the chip but doesn't
ack them. Then when a pmac_zilog port is used, the machine locks up with
"unexpected interrupt".

This can happen in pmz_shutdown() since the irq is freed before the
channel interrupts are disabled.

Fix this by clearing interrupt enable bits before the handler is
uninstalled. Also move the interrupt control bit flipping into a separate
pmz_interrupt_control() routine. Replace all instances of these operations
with calls to this routine. Omit the zssync() calls that seem to serve no
purpose.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Finn Thain authored and Benjamin Herrenschmidt committed Dec 8, 2011
1 parent 2fde6d2 commit 7cf82b1
Showing 1 changed file with 52 additions and 50 deletions.
102 changes: 52 additions & 50 deletions drivers/tty/serial/pmac_zilog.c
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Original file line number Diff line number Diff line change
Expand Up @@ -216,6 +216,18 @@ static void pmz_maybe_update_regs(struct uart_pmac_port *uap)
}
}

static void pmz_interrupt_control(struct uart_pmac_port *uap, int enable)
{
if (enable) {
uap->curregs[1] |= INT_ALL_Rx | TxINT_ENAB;
if (!ZS_IS_EXTCLK(uap))
uap->curregs[1] |= EXT_INT_ENAB;
} else {
uap->curregs[1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
}
write_zsreg(uap, R1, uap->curregs[1]);
}

static struct tty_struct *pmz_receive_chars(struct uart_pmac_port *uap)
{
struct tty_struct *tty = NULL;
Expand Down Expand Up @@ -339,9 +351,7 @@ static struct tty_struct *pmz_receive_chars(struct uart_pmac_port *uap)

return tty;
flood:
uap->curregs[R1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
write_zsreg(uap, R1, uap->curregs[R1]);
zssync(uap);
pmz_interrupt_control(uap, 0);
pmz_error("pmz: rx irq flood !\n");
return tty;
}
Expand Down Expand Up @@ -990,12 +1000,9 @@ static int pmz_startup(struct uart_port *port)
if (ZS_IS_IRDA(uap))
pmz_irda_reset(uap);

/* Enable interrupts emission from the chip */
/* Enable interrupt requests for the channel */
spin_lock_irqsave(&port->lock, flags);
uap->curregs[R1] |= INT_ALL_Rx | TxINT_ENAB;
if (!ZS_IS_EXTCLK(uap))
uap->curregs[R1] |= EXT_INT_ENAB;
write_zsreg(uap, R1, uap->curregs[R1]);
pmz_interrupt_control(uap, 1);
spin_unlock_irqrestore(&port->lock, flags);

pmz_debug("pmz: startup() done.\n");
Expand All @@ -1015,6 +1022,25 @@ static void pmz_shutdown(struct uart_port *port)

mutex_lock(&pmz_irq_mutex);

spin_lock_irqsave(&port->lock, flags);

if (!ZS_IS_ASLEEP(uap)) {
/* Disable interrupt requests for the channel */
pmz_interrupt_control(uap, 0);

if (!ZS_IS_CONS(uap)) {
/* Disable receiver and transmitter */
uap->curregs[R3] &= ~RxENABLE;
uap->curregs[R5] &= ~TxENABLE;

/* Disable break assertion */
uap->curregs[R5] &= ~SND_BRK;
pmz_maybe_update_regs(uap);
}
}

spin_unlock_irqrestore(&port->lock, flags);

/* Release interrupt handler */
free_irq(uap->port.irq, uap);

Expand All @@ -1025,29 +1051,8 @@ static void pmz_shutdown(struct uart_port *port)
if (!ZS_IS_OPEN(uap->mate))
pmz_get_port_A(uap)->flags &= ~PMACZILOG_FLAG_IS_IRQ_ON;

/* Disable interrupts */
if (!ZS_IS_ASLEEP(uap)) {
uap->curregs[R1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
write_zsreg(uap, R1, uap->curregs[R1]);
zssync(uap);
}

if (ZS_IS_CONS(uap) || ZS_IS_ASLEEP(uap)) {
spin_unlock_irqrestore(&port->lock, flags);
mutex_unlock(&pmz_irq_mutex);
return;
}

/* Disable receiver and transmitter. */
uap->curregs[R3] &= ~RxENABLE;
uap->curregs[R5] &= ~TxENABLE;

/* Disable all interrupts and BRK assertion. */
uap->curregs[R5] &= ~SND_BRK;
pmz_maybe_update_regs(uap);

/* Shut the chip down */
pmz_set_scc_power(uap, 0);
if (!ZS_IS_ASLEEP(uap) && !ZS_IS_CONS(uap))
pmz_set_scc_power(uap, 0); /* Shut the chip down */

spin_unlock_irqrestore(&port->lock, flags);

Expand Down Expand Up @@ -1352,19 +1357,15 @@ static void pmz_set_termios(struct uart_port *port, struct ktermios *termios,
spin_lock_irqsave(&port->lock, flags);

/* Disable IRQs on the port */
uap->curregs[R1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
write_zsreg(uap, R1, uap->curregs[R1]);
pmz_interrupt_control(uap, 0);

/* Setup new port configuration */
__pmz_set_termios(port, termios, old);

/* Re-enable IRQs on the port */
if (ZS_IS_OPEN(uap)) {
uap->curregs[R1] |= INT_ALL_Rx | TxINT_ENAB;
if (!ZS_IS_EXTCLK(uap))
uap->curregs[R1] |= EXT_INT_ENAB;
write_zsreg(uap, R1, uap->curregs[R1]);
}
if (ZS_IS_OPEN(uap))
pmz_interrupt_control(uap, 1);

spin_unlock_irqrestore(&port->lock, flags);
}

Expand Down Expand Up @@ -1671,14 +1672,17 @@ static int pmz_suspend(struct macio_dev *mdev, pm_message_t pm_state)
spin_lock_irqsave(&uap->port.lock, flags);

if (ZS_IS_OPEN(uap) || ZS_IS_CONS(uap)) {
/* Disable receiver and transmitter. */
/* Disable interrupt requests for the channel */
pmz_interrupt_control(uap, 0);

/* Disable receiver and transmitter */
uap->curregs[R3] &= ~RxENABLE;
uap->curregs[R5] &= ~TxENABLE;

/* Disable all interrupts and BRK assertion. */
uap->curregs[R1] &= ~(EXT_INT_ENAB | TxINT_ENAB | RxINT_MASK);
/* Disable break assertion */
uap->curregs[R5] &= ~SND_BRK;
pmz_load_zsregs(uap, uap->curregs);

uap->flags |= PMACZILOG_FLAG_IS_ASLEEP;
mb();
}
Expand Down Expand Up @@ -1738,14 +1742,6 @@ static int pmz_resume(struct macio_dev *mdev)
/* Take care of config that may have changed while asleep */
__pmz_set_termios(&uap->port, &uap->termios_cache, NULL);

if (ZS_IS_OPEN(uap)) {
/* Enable interrupts */
uap->curregs[R1] |= INT_ALL_Rx | TxINT_ENAB;
if (!ZS_IS_EXTCLK(uap))
uap->curregs[R1] |= EXT_INT_ENAB;
write_zsreg(uap, R1, uap->curregs[R1]);
}

spin_unlock_irqrestore(&uap->port.lock, flags);

if (ZS_IS_CONS(uap))
Expand All @@ -1757,6 +1753,12 @@ static int pmz_resume(struct macio_dev *mdev)
enable_irq(uap->port.irq);
}

if (ZS_IS_OPEN(uap)) {
spin_lock_irqsave(&uap->port.lock, flags);
pmz_interrupt_control(uap, 1);
spin_unlock_irqrestore(&uap->port.lock, flags);
}

bail:
mutex_unlock(&state->port.mutex);
mutex_unlock(&pmz_irq_mutex);
Expand Down

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