rtc: at91sam9 RTC support (RTT and/or RTC)

AT91sam9 RTC support, primarily in the form of an RTT-as-RTC driver that was
extracted from 2.6.23-at91 patch and updated:

 - Relies on now-merged platform updates, which associate the RTT
   hardware address with each RTT and use the "at91_rtt" name.

 - RTC framework related fixes and cleanups, notably:
    * removed now-needless suspend/resume clock offset logic
    * alarm read/write now respects the "enabled" flag
    * suspend always disables update irqs
    * shutdown (and startup) disables all irqs

 - Misc cleanup:
    * use dev_*() messaging
    * add comments
    * remove globals,
    * ... etc

 - Don't force use of RTT0 and GPBR0.  Either resource may need
   to be used for other purposes (like NO_HZ support).

 - Update "AT91RM9200 RTC" Kconfig to allow it on SAM9RL chips
   (it has both RTT and RTC).

Driver binding uses bus_find_device() to avoid needing any kind of "timer
library" code when there's more than one RTT module.  (This timer can be used
as an RTC, to support NO_HZ operation, or potentially for other stuff.  The
choice is a per-system policy.)
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Michel Benoit <murpme@gmail.com>
Cc: Nicolas Ferre <nicolas.ferre@rfo.atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/Kconfig

@@ -469,10 +469,47 @@ config RTC_DRV_AT32AP700X
 	  AT32AP700x family processors.
 
 config RTC_DRV_AT91RM9200
-	tristate "AT91RM9200"
-	depends on ARCH_AT91RM9200
-	help
-	  Driver for the Atmel AT91RM9200's internal RTC (Realtime Clock).
+	tristate "AT91RM9200 or AT91SAM9RL"
+	depends on ARCH_AT91RM9200 || ARCH_AT91SAM9RL
+	help
+	  Driver for the internal RTC (Realtime Clock) module found on
+	  Atmel AT91RM9200's and AT91SAM9RL chips.  On SAM9RL chips
+	  this is powered by the backup power supply.
+
+config RTC_DRV_AT91SAM9
+	tristate "AT91SAM9x"
+	depends on ARCH_AT91 && !(ARCH_AT91RM9200 || ARCH_AT91X40)
+	help
+	  RTC driver for the Atmel AT91SAM9x internal RTT (Real Time Timer).
+	  These timers are powered by the backup power supply (such as a
+	  small coin cell battery), but do not need to be used as RTCs.
+
+	  (On AT91SAM9rl chips you probably want to use the dedicated RTC
+	  module and leave the RTT available for other uses.)
+
+config RTC_DRV_AT91SAM9_RTT
+	int
+	range 0 1
+	default 0
+	prompt "RTT module Number" if ARCH_AT91SAM9263
+	depends on RTC_DRV_AT91SAM9
+	help
+	  More than one RTT module is available.  You can choose which
+	  one will be used as an RTC.  The default of zero is normally
+	  OK to use, though some systems use that for non-RTC purposes.
+
+config RTC_DRV_AT91SAM9_GPBR
+	int
+	range 0 3 if !ARCH_AT91SAM9263
+	range 0 15 if ARCH_AT91SAM9263
+	default 0
+	prompt "Backup Register Number"
+	depends on RTC_DRV_AT91SAM9
+	help
+	  The RTC driver needs to use one of the General Purpose Backup
+	  Registers (GPBRs) as well as the RTT.  You can choose which one
+	  will be used.  The default of zero is normally OK to use, but
+	  on some systems other software needs to use that register.
 
 config RTC_DRV_BFIN
 	tristate "Blackfin On-Chip RTC"

drivers/rtc/Makefile

@@ -19,6 +19,7 @@ rtc-core-$(CONFIG_RTC_INTF_SYSFS) += rtc-sysfs.o
 
 obj-$(CONFIG_RTC_DRV_AT32AP700X)+= rtc-at32ap700x.o
 obj-$(CONFIG_RTC_DRV_AT91RM9200)+= rtc-at91rm9200.o
+obj-$(CONFIG_RTC_DRV_AT91SAM9)	+= rtc-at91sam9.o
 obj-$(CONFIG_RTC_DRV_BFIN)	+= rtc-bfin.o
 obj-$(CONFIG_RTC_DRV_CMOS)	+= rtc-cmos.o
 obj-$(CONFIG_RTC_DRV_DS1216)	+= rtc-ds1216.o