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>

1 files changed, 41 insertions, 4 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 484de8e4c5ae..6402d699072b 100644
--- a/drivers/rtc/Kconfig
+++ b/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"