[PATCH 01/16] pmac_zilog: fix unexpected irq

Finn Thain
2011-11-24T14:35:05Z

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 opened and SCC chip interrupts
become enabled, the machine locks up with "unexpected interrupt" because
request_irq() hasn't happened yet.

Fix this by setting the SCC master interrupt enable bit only after the
handler is installed. This is achieved by extracting that operation out of
__pmz_startup() and placing it into a seperate routine.

A similar problem arises when the irq is freed. Fix this by resetting the
chip first (on m68k mac).

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

---

This patch has been tested on a variety of m68k Macs but no PowerMacs.

I am re-sending this patch Cc linux-serial. It still needs a suitable ack
so that Geert can push it through his tree.

Index: linux-m68k/drivers/tty/serial/pmac_zilog.c
===================================================================
--- linux-m68k.orig/drivers/tty/serial/pmac_zilog.c 2011-10-22 23:02:22.000000000 +1100
+++ linux-m68k/drivers/tty/serial/pmac_zilog.c 2011-10-22 23:02:38.000000000 +1100
@@ -910,8 +910,8 @@ static int __pmz_startup(struct uart_pma
/* Clear handshaking, enable BREAK interrupts */
uap->curregs[R15] = BRKIE;

- /* Master interrupt enable */
- uap->curregs[R9] |= NV | MIE;
+ /* No vector */
+ uap->curregs[R9] |= NV;

pmz_load_zsregs(uap, uap->curregs);

@@ -925,6 +925,17 @@ static int __pmz_startup(struct uart_pma
return pwr_delay;
}

+static void pmz_master_int_control(struct uart_pmac_port *uap, int enable)
+{
+ if (enable) {
+ uap->curregs[R9] |= MIE; /* Master interrupt enable */
+ write_zsreg(uap, R9, uap->curregs[R9]);
+ } else {
+ uap->curregs[R9] &= ~MIE;
+ write_zsreg(uap, 9, FHWRES);
+ }
+}
+
static void pmz_irda_reset(struct uart_pmac_port *uap)
{
uap->curregs[R5] |= DTR;
@@ -976,6 +987,19 @@ static int pmz_startup(struct uart_port
return -ENXIO;
}

+ /*
+ * Most 68k Mac models cannot mask the SCC IRQ so they must enable
+ * interrupts after the handler is installed and not before.
+ */
+#ifndef CONFIG_MAC
+ if (!ZS_IS_CONS(uap))
+#endif
+ {
+ spin_lock_irqsave(&port->lock, flags);
+ pmz_master_int_control(uap, 1);
+ spin_unlock_irqrestore(&port->lock, flags);
+ }
+
mutex_unlock(&pmz_irq_mutex);

/* Right now, we deal with delay by blocking here, I'll be
@@ -1015,6 +1039,11 @@ static void pmz_shutdown(struct uart_por

mutex_lock(&pmz_irq_mutex);

+#ifdef CONFIG_MAC
+ if (!ZS_IS_OPEN(uap->mate))
+ pmz_master_int_control(uap, 0);
+#endif
+
/* Release interrupt handler */
free_irq(uap->port.irq, uap);

@@ -1734,6 +1763,7 @@ static int pmz_resume(struct macio_dev *
goto bail;
}
pwr_delay = __pmz_startup(uap);
+ pmz_master_int_control(uap, 1);

/* Take care of config that may have changed while asleep */
__pmz_set_termios(&uap->port, &uap->termios_cache, NULL);
@@ -2178,6 +2208,9 @@ static int __init pmz_console_setup(stru
* Enable the hardware
*/
pwr_delay = __pmz_startup(uap);
+#ifndef CONFIG_MAC
+ pmz_master_int_control(uap, 1);
+#endif
if (pwr_delay)
mdelay(pwr_delay);