MIPS: Add basic CPUFreq options.

This patch adds basic options for MIPS CPUFreq support.

Since the cp0 timer's frequency is based on the processor clockrate it can
not be used with CPUFReq; an additional external timer is required.
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: cpufreq@vger.kernel.org,
Cc: Dave Jones <davej@redhat.com>,
Cc: Dominik Brodowski <linux@dominikbrodowski.net>,
Cc: yanh@lemote.com
Cc: huhb@lemote.com,
Patchwork: http://patchwork.linux-mips.org/patch/659/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -2161,6 +2161,7 @@ config MMU
 
 config I8253
 	bool
+	select MIPS_EXTERNAL_TIMER
 
 config ZONE_DMA32
 	bool
@@ -2237,6 +2238,8 @@ source "kernel/power/Kconfig"
 
 endmenu
 
+source "arch/mips/kernel/cpufreq/Kconfig"
+
 source "net/Kconfig"
 
 source "drivers/Kconfig"

arch/mips/kernel/cpufreq/Kconfig

+#
+# CPU Frequency scaling
+#
+
+config MIPS_EXTERNAL_TIMER
+	bool
+
+config MIPS_CPUFREQ
+	bool
+	default y
+	depends on CPU_SUPPORTS_CPUFREQ && MIPS_EXTERNAL_TIMER
+
+if MIPS_CPUFREQ
+
+menu "CPU Frequency scaling"
+
+source "drivers/cpufreq/Kconfig"
+
+if CPU_FREQ
+
+comment "CPUFreq processor drivers"
+
+endif	# CPU_FREQ
+
+endmenu
+
+endif	# MIPS_CPUFREQ