rtc: add driver for DS1685 family of real time clocks

This adds a driver for the Dallas/Maxim DS1685-family of RTC chips.  It
supports the DS1685/DS1687, DS1688/DS1691, DS1689/DS1693, DS17285/DS17287,
DS17485/DS17487, and DS17885/DS17887 RTC chips.  These chips are commonly
found in SGI O2 and SGI Octane systems.  It was originally derived from a
driver patch submitted by Matthias Fuchs many years ago for use in
EPPC-405-UC modules, which also used these RTCs.  In addition to the
time-keeping functions, this RTC also handles the shutdown mechanism of
the O2 and Octane and acts as a partial NVRAM for the boot PROMS in these
systems.

Verified on both an SGI O2 and an SGI Octane.

Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 90 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 3bc9ddbe5cf7..0cf2e1d9cb17 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -801,6 +801,96 @@ config RTC_DRV_DS1553
           This driver can also be built as a module. If so, the module
           will be called rtc-ds1553.
 
+config RTC_DRV_DS1685_FAMILY
+        tristate "Dallas/Maxim DS1685 Family"
+        help
+          If you say yes here you get support for the Dallas/Maxim DS1685
+          family of real time chips.  This family includes the DS1685/DS1687,
+          DS1689/DS1693, DS17285/DS17287, DS17485/DS17487, and
+          DS17885/DS17887 chips.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-ds1685.
+
+choice
+        prompt "Subtype"
+        depends on RTC_DRV_DS1685_FAMILY
+        default RTC_DRV_DS1685
+
+config RTC_DRV_DS1685
+        bool "DS1685/DS1687"
+        help
+          This enables support for the Dallas/Maxim DS1685/DS1687 real time
+          clock chip.
+
+          This chip is commonly found in SGI O2 (IP32) and SGI Octane (IP30)
+          systems, as well as EPPC-405-UC modules by electronic system design
+          GmbH.
+
+config RTC_DRV_DS1689
+        bool "DS1689/DS1693"
+        help
+          This enables support for the Dallas/Maxim DS1689/DS1693 real time
+          clock chip.
+
+          This is an older RTC chip, supplanted by the DS1685/DS1687 above,
+          which supports a few minor features such as Vcc, Vbat, and Power
+          Cycle counters, plus a customer-specific, 8-byte ROM/Serial number.
+
+          It also works for the even older DS1688/DS1691 RTC chips, which are
+          virtually the same and carry the same model number.  Both chips
+          have 114 bytes of user NVRAM.
+
+config RTC_DRV_DS17285
+        bool "DS17285/DS17287"
+        help
+          This enables support for the Dallas/Maxim DS17285/DS17287 real time
+          clock chip.
+
+          This chip features 2kb of extended NV-SRAM.  It may possibly be
+          found in some SGI O2 systems (rare).
+
+config RTC_DRV_DS17485
+        bool "DS17485/DS17487"
+        help
+          This enables support for the Dallas/Maxim DS17485/DS17487 real time
+          clock chip.
+
+          This chip features 4kb of extended NV-SRAM.
+
+config RTC_DRV_DS17885
+        bool "DS17885/DS17887"
+        help
+          This enables support for the Dallas/Maxim DS17885/DS17887 real time
+          clock chip.
+
+          This chip features 8kb of extended NV-SRAM.
+
+endchoice
+
+config RTC_DS1685_PROC_REGS
+        bool "Display register values in /proc"
+        depends on RTC_DRV_DS1685_FAMILY && PROC_FS
+        help
+          Enable this to display a readout of all of the RTC registers in
+          /proc/drivers/rtc.  Keep in mind that this can potentially lead
+          to lost interrupts, as reading Control Register C will clear
+          all pending IRQ flags.
+
+          Unless you are debugging this driver, choose N.
+
+config RTC_DS1685_SYSFS_REGS
+        bool "SysFS access to RTC register bits"
+        depends on RTC_DRV_DS1685_FAMILY && SYSFS
+        help
+          Enable this to provide access to the RTC control register bits
+          in /sys.  Some of the bits are read-write, others are read-only.
+
+          Keep in mind that reading Control C's bits automatically clears
+          all pending IRQ flags - this can cause lost interrupts.
+
+          If you know that you need access to these bits, choose Y, Else N.
+
 config RTC_DRV_DS1742
         tristate "Maxim/Dallas DS1742/1743"
         depends on HAS_IOMEM