RTC: use fallback IRQ if PNP tables don't provide one

Intel Macs (and possibly other machines) provide a PNP entry for the RTC,
but provide no IRQ.  As a result the rtc-cmos driver doesn't allow wakeup
alarms.  If the RTC is located at the legacy ioport range, assume that it's
on IRQ 8 unless the tables say otherwise.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Matthieu CASTET <castet.matthieu@free.fr>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 6085261aa2c1..e24ea82dc35b 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -641,9 +641,16 @@ cmos_pnp_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
          * drivers can't provide shutdown() methods to disable IRQs.
          * Or better yet, fix PNP to allow those methods...
          */
-        return cmos_do_probe(&pnp->dev,
-                        &pnp->res.port_resource[0],
-                        pnp->res.irq_resource[0].start);
+        if (pnp_port_start(pnp,0) == 0x70 && !pnp_irq_valid(pnp,0))
+                /* Some machines contain a PNP entry for the RTC, but
+                 * don't define the IRQ. It should always be safe to
+                 * hardcode it in these cases
+                 */
+                return cmos_do_probe(&pnp->dev, &pnp->res.port_resource[0], 8);
+        else
+                return cmos_do_probe(&pnp->dev,
+                                     &pnp->res.port_resource[0],
+                                     pnp->res.irq_resource[0].start);
 }
 
 static void __exit cmos_pnp_remove(struct pnp_dev *pnp)