clocksource: apb: Share APB timer code with other platforms

The APB timers are an IP block from Synopsys (DesignWare APB timers)
and are also found in other systems including ARM SoC's.  This patch
adds functions for creating clock_event_devices and clocksources from
APB timers but does not do the resource allocation.  This is handled
in a higher layer to allow the timers to be created from multiple
methods such as platform_devices.

Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Jacob Pan <[email protected]>
Signed-off-by: Jamie Iles <[email protected]>
Signed-off-by: John Stultz <[email protected]>

arch/x86/Kconfig

@@ -617,6 +617,7 @@ config HPET_EMULATE_RTC
 config APB_TIMER
        def_bool y if MRST
        prompt "Langwell APB Timer Support" if X86_MRST
+       select DW_APB_TIMER
        help
          APB timer is the replacement for 8254, HPET on X86 MID platforms.
          The APBT provides a stable time base on SMP

arch/x86/include/asm/apb_timer.h

@@ -18,33 +18,15 @@
 
 #ifdef CONFIG_APB_TIMER
 
-/* Langwell DW APB timer registers */
-#define APBTMR_N_LOAD_COUNT    0x00
-#define APBTMR_N_CURRENT_VALUE 0x04
-#define APBTMR_N_CONTROL       0x08
-#define APBTMR_N_EOI           0x0c
-#define APBTMR_N_INT_STATUS    0x10
-
-#define APBTMRS_INT_STATUS     0xa0
-#define APBTMRS_EOI            0xa4
-#define APBTMRS_RAW_INT_STATUS 0xa8
-#define APBTMRS_COMP_VERSION   0xac
-#define APBTMRS_REG_SIZE       0x14
-
-/* register bits */
-#define APBTMR_CONTROL_ENABLE  (1<<0)
-#define APBTMR_CONTROL_MODE_PERIODIC   (1<<1) /*1: periodic 0:free running */
-#define APBTMR_CONTROL_INT     (1<<2)
-
 /* default memory mapped register base */
 #define LNW_SCU_ADDR           0xFF100000
 #define LNW_EXT_TIMER_OFFSET   0x1B800
 #define APBT_DEFAULT_BASE      (LNW_SCU_ADDR+LNW_EXT_TIMER_OFFSET)
 #define LNW_EXT_TIMER_PGOFFSET         0x800
 
 /* APBT clock speed range from PCLK to fabric base, 25-100MHz */
-#define APBT_MAX_FREQ          50
-#define APBT_MIN_FREQ          1
+#define APBT_MAX_FREQ          50000000
+#define APBT_MIN_FREQ          1000000
 #define APBT_MMAP_SIZE         1024
 
 #define APBT_DEV_USED  1