cs5535: add a generic clock event MFGPT driver

This is based on the old code in arch/x86/kernel/mfgpt_32.c, but is
modular and not Geode-specific.  There's no reason why the clock event
device needs to be registered so early at boot; the clockevent code is
perfectly capable of dynamic switching.

[akpm@linux-foundation.org: add linux/irq.h include]
Signed-off-by: Andres Salomon <dilinger@collabora.co.uk>
Cc: Jordan Crouse <jordan@cosmicpenguin.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Chris Ball <cjb@laptop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
new file mode 100644
index 0000000..08f726c
--- /dev/null
+++ b/drivers/clocksource/Kconfig
@@ -0,0 +1,9 @@
+config CS5535_CLOCK_EVENT_SRC
+	tristate "CS5535/CS5536 high-res timer (MFGPT) events"
+	depends on GENERIC_TIME && GENERIC_CLOCKEVENTS && CS5535_MFGPT
+	help
+	  This driver provides a clock event source based on the MFGPT
+	  timer(s) in the CS5535 and CS5536 companion chips.
+	  MFGPTs have a better resolution and max interval than the
+	  generic PIT, and are suitable for use as high-res timers.
+