cope with PNPACPI tables missing an RTC entry

From: David Brownell <[email protected]>

A bugzilla entry (http://bugzilla.kernel.org/show_bug.cgi?id=11580)
reports that some PNPACPI tables don't list RTC devices; they are instead glommed into a generic "system resources" entry.

Address that on x86 (while ignoring ia64, the other user of ACPI) by having ACPI glue check for that case, and if necessary then setting up a platform device and having rtc_cmos use it.

Signed-off-by David Brownell <[email protected]>

Reported-by Rik Theys <[email protected]>

---
Seems like a candidate for 2.6.27-final and for backporting. There's a Fedora kernel report for this too. Workaround is simple (see the bug report) but less functional.

 arch/x86/kernel/rtc.c         |   13 ++++++++++++-
 drivers/acpi/glue.c           |   16 +++++++++++++++-
 drivers/pnp/core.c            |    8 ++++++++
 drivers/rtc/rtc-cmos.c        |    4 ++--
 include/asm-x86/mc146818rtc.h |    5 +++++
 include/linux/pnp.h           |    1 +
 6 files changed, 43 insertions(+), 4 deletions(-)

arch/x86/kernel/rtc.c +12 -1

@@ -220,11 +220,22 @@ static struct platform_device rtc_device
 	.num_resources	= ARRAY_SIZE(rtc_resources),
 };
 
+#ifdef CONFIG_PNP
+/* PNPACPI tables sometimes omit the RTC, or are ignored */
+struct device *__init add_nonpnp_rtc_cmos(void)
+{
+	if (!rtc_device.dev.bus)
+		platform_device_register(&rtc_device);
+	return &rtc_device.dev;
+}
+#endif
+
 static __init int add_rtc_cmos(void)
 {
 #ifdef CONFIG_PNP
+	/* in case of pnpacpi=off */
 	if (!pnp_platform_devices)
-		platform_device_register(&rtc_device);
+		add_nonpnp_rtc_cmos();
 #else
 	platform_device_register(&rtc_device);
 #endif /* CONFIG_PNP */

drivers/acpi/glue.c +15 -1

@@ -338,7 +338,21 @@ static int __init pnp_match(struct devic
 
 static struct device *__init get_rtc_dev(void)
 {
-	return bus_find_device(&pnp_bus_type, NULL, NULL, pnp_match);
+	struct device *rtc;
+
+	/* return RTC from PNPACPI tables */
+	rtc = bus_find_device(&pnp_bus_type, NULL, NULL, pnp_match);
+
+#ifdef ARCH_PNP_RTC_WORKAROUND
+	/* cope with buggy PNPACPI tables (like the HP DL3x0 servers
+	 * which have no RTC device listed), and with pnpacpi=off
+	 */
+	if (!rtc) {
+		pnp_rtc_missing = true;
+		rtc = add_nonpnp_rtc_cmos();
+	}
+#endif
+	return rtc;
 }
 
 static int __init acpi_rtc_init(void)

drivers/pnp/core.c +8 -0

@@ -25,10 +25,18 @@ DEFINE_SPINLOCK(pnp_lock);
  * ACPI or PNPBIOS should tell us about all platform devices, so we can
  * skip some blind probes.  ISAPNP typically enumerates only plug-in ISA
  * devices, not built-in things like COM ports.
+ *
+ * Sometimes ACPI tables omit devices like RTCs, which can be critical.
+ * To avoid legacy poke-the-hardware-and-guess drivers (unfriendly to
+ * the driver model), something else creates a (platform) device node;
+ * and drivers must know to kick-in their non-PNP (non-PC) bus glue.
  */
 int pnp_platform_devices;
 EXPORT_SYMBOL(pnp_platform_devices);
 
+bool pnp_rtc_missing;
+EXPORT_SYMBOL(pnp_rtc_missing);
+
 void *pnp_alloc(long size)
 {
 	void *result;

drivers/rtc/rtc-cmos.c +2 -2

@@ -1137,7 +1137,7 @@ static struct platform_driver cmos_platf
 static int __init cmos_init(void)
 {
 #ifdef	CONFIG_PNP
-	if (pnp_platform_devices)
+	if (pnp_platform_devices && !pnp_rtc_missing)
 		return pnp_register_driver(&cmos_pnp_driver);
 	else
 		return platform_driver_probe(&cmos_platform_driver,

@@ -1152,7 +1152,7 @@ module_init(cmos_init);
 static void __exit cmos_exit(void)
 {
 #ifdef	CONFIG_PNP
-	if (pnp_platform_devices)
+	if (pnp_platform_devices && !pnp_rtc_missing)
 		pnp_unregister_driver(&cmos_pnp_driver);
 	else
 		platform_driver_unregister(&cmos_platform_driver);

include/asm-x86/mc146818rtc.h +5 -0

@@ -101,4 +101,9 @@ extern unsigned long mach_get_cmos_time(
 
 #define RTC_IRQ 8
 
+#ifdef CONFIG_PNP
+#define ARCH_PNP_RTC_WORKAROUND
+extern struct device *add_nonpnp_rtc_cmos(void);
+#endif
+
 #endif /* _ASM_MC146818RTC_H */

include/linux/pnp.h +1 -0

@@ -420,6 +420,7 @@ int pnp_device_attach(struct pnp_dev *pn
 void pnp_device_detach(struct pnp_dev *pnp_dev);
 extern struct list_head pnp_global;
 extern int pnp_platform_devices;
+extern bool pnp_rtc_missing;
 
 /* multidevice card support */
 struct pnp_dev *pnp_request_card_device(struct pnp_card_link *clink,