mmtimer: Remove the SGI SN2 mmtimer driver

This driver supports direct system clock access on the ancient SGI SN2
IA64 systems, and implement the only non-builtin k_clock instance.
Remove it as any remaining IA64 altix user will be running just as old
distros anyway.

Dimitri Sivanich stated: "Since this is SN2 specific, this can be removed."

Note that this does not affect the never uv_mmtimer driver for x86-based
Altix systems.

[ tglx: Added comment to CLOCK_SGI_CYCLE ]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Travis <mike.travis@hpe.com>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Link: http://lkml.kernel.org/r/20170526090311.3377-2-hch@lst.de

drivers/char/Kconfig

@@ -539,15 +539,6 @@ config HANGCHECK_TIMER
 	  out to lunch past a certain margin.  It can reboot the system
 	  or merely print a warning.
 
-config MMTIMER
-	tristate "MMTIMER Memory mapped RTC for SGI Altix"
-	depends on IA64_GENERIC || IA64_SGI_SN2
-	depends on POSIX_TIMERS
-	default y
-	help
-	  The mmtimer device allows direct userspace access to the
-	  Altix system timer.
-
 config UV_MMTIMER
 	tristate "UV_MMTIMER Memory mapped RTC for SGI UV"
 	depends on X86_UV

drivers/char/Makefile

@@ -10,7 +10,6 @@ obj-$(CONFIG_VIRTIO_CONSOLE)	+= virtio_console.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
 obj-$(CONFIG_SGI_SNSC)		+= snsc.o snsc_event.o
 obj-$(CONFIG_MSPEC)		+= mspec.o
-obj-$(CONFIG_MMTIMER)		+= mmtimer.o
 obj-$(CONFIG_UV_MMTIMER)	+= uv_mmtimer.o
 obj-$(CONFIG_IBM_BSR)		+= bsr.o
 obj-$(CONFIG_SGI_MBCS)		+= mbcs.o

include/uapi/linux/time.h

@@ -54,7 +54,11 @@ struct itimerval {
 #define CLOCK_BOOTTIME			7
 #define CLOCK_REALTIME_ALARM		8
 #define CLOCK_BOOTTIME_ALARM		9
-#define CLOCK_SGI_CYCLE			10	/* Hardware specific */
+/*
+ * The driver implementing this got removed. The clock ID is kept as a
+ * place holder. Do not reuse!
+ */
+#define CLOCK_SGI_CYCLE			10
 #define CLOCK_TAI			11
 
 #define MAX_CLOCKS			16