rtc-cmos: look for PNP RTC first, then for platform RTC

We shouldn't rely on "pnp_platform_devices" to tell us whether there
is a PNP RTC device.

I introduced "pnp_platform_devices", but I think it was a mistake.
All it tells us is whether we found any PNPBIOS or PNPACPI devices.
Many machines have some PNP devices, but do not describe the RTC
via PNP.  On those machines, we need to do the platform driver probe
to find the RTC.

We should just register the PNP driver and see whether it claims anything.
If we don't find a PNP RTC, fall back to the platform driver probe.

This (in conjunction with the arch/x86/kernel/rtc.c patch to add
a platform RTC device when PNP doesn't have one) should resolve
these issues:

    http://bugzilla.kernel.org/show_bug.cgi?id=11580
    https://bugzilla.redhat.com/show_bug.cgi?id=451188

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Reported-by: Rik Theys <rik.theys@esat.kuleuven.be>
Reported-by: shr_msn@yahoo.com.tw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 15 deletions

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 6778f82bad24..963ad0b6a4e9 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -1120,29 +1120,32 @@ static struct platform_driver cmos_platform_driver = {
 
 static int __init cmos_init(void)
 {
+        int retval = 0;
+
 #ifdef  CONFIG_PNP
-        if (pnp_platform_devices)
-                return pnp_register_driver(&cmos_pnp_driver);
-        else
-                return platform_driver_probe(&cmos_platform_driver,
-                        cmos_platform_probe);
-#else
-        return platform_driver_probe(&cmos_platform_driver,
-                        cmos_platform_probe);
-#endif /* CONFIG_PNP */
+        pnp_register_driver(&cmos_pnp_driver);
+#endif
+
+        if (!cmos_rtc.dev)
+                retval = platform_driver_probe(&cmos_platform_driver,
+                                               cmos_platform_probe);
+
+        if (retval == 0)
+                return 0;
+
+#ifdef  CONFIG_PNP
+        pnp_unregister_driver(&cmos_pnp_driver);
+#endif
+        return retval;
 }
 module_init(cmos_init);
 
 static void __exit cmos_exit(void)
 {
 #ifdef  CONFIG_PNP
-        if (pnp_platform_devices)
-                pnp_unregister_driver(&cmos_pnp_driver);
-        else
-                platform_driver_unregister(&cmos_platform_driver);
-#else
+        pnp_unregister_driver(&cmos_pnp_driver);
+#endif
         platform_driver_unregister(&cmos_platform_driver);
-#endif /* CONFIG_PNP */
 }
 module_exit(cmos_exit);