[MIPS] Fixup migration to GENERIC_TIME

Since we already moved to GENERIC_TIME, we should implement alternatives
of old do_gettimeoffset routines to get sub-jiffies resolution from
gettimeofday().  This patch includes:

 * MIPS clocksource support (based on works by Manish Lachwani).
 * remove unused gettimeoffset routines and related codes.
 * remove unised 64bit do_div64_32().
 * simplify mips_hpt_init. (no argument needed, __init tag)
 * simplify c0_hpt_timer_init. (no need to write to c0_count)
 * remove some hpt_init routines.
 * mips_hpt_mask variable to specify bitmask of hpt value.
 * convert jmr3927_do_gettimeoffset to jmr3927_hpt_read.
 * convert ip27_do_gettimeoffset to ip27_hpt_read.
 * convert bcm1480_do_gettimeoffset to bcm1480_hpt_read.
 * simplify sb1250 hpt functions. (no need to subtract and shift)
    
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

13 files changed, 103 insertions, 522 deletions

diff --git a/Documentation/mips/time.README b/Documentation/mips/time.README
index e1304b6bc483..a4ce603ed3b3 100644
--- a/Documentation/mips/time.README
+++ b/Documentation/mips/time.README
@@ -38,19 +38,14 @@ The new time code provide the following services:
 
   a) Implements functions required by Linux common code:
         time_init
-        do_gettimeofday
-        do_settimeofday
 
   b) provides an abstraction of RTC and null RTC implementation as default.
         extern unsigned long (*rtc_get_time)(void);
         extern int (*rtc_set_time)(unsigned long);
 
-  c) a set of gettimeoffset functions for different CPUs and different
-     needs.
-
-  d) high-level and low-level timer interrupt routines where the timer 
-     interrupt source  may or may not be the CPU timer.  The high-level 
-     routine is dispatched through do_IRQ() while the low-level is 
+  c) high-level and low-level timer interrupt routines where the timer
+     interrupt source  may or may not be the CPU timer.  The high-level
+     routine is dispatched through do_IRQ() while the low-level is
      dispatched in assemably code (usually int-handler.S)
 
 
@@ -73,8 +68,7 @@ the following functions or values:
   c) (optional) board-specific RTC routines.
 
   d) (optional) mips_hpt_frequency - It must be definied if the board
-     is using CPU counter for timer interrupt or it is using fixed rate
-     gettimeoffset().
+     is using CPU counter for timer interrupt.
 
 
 PORTING GUIDE
@@ -89,16 +83,6 @@ Step 1: decide how you like to implement the time services.
      If the answer is no, you need a timer to provide the timer interrupt
      at 100 HZ speed.
 
-     You cannot use the fast gettimeoffset functions, i.e.,
-
-        unsigned long fixed_rate_gettimeoffset(void);
-        unsigned long calibrate_div32_gettimeoffset(void);
-        unsigned long calibrate_div64_gettimeoffset(void);
-
-    You can use null_gettimeoffset() will gives the same time resolution as
-    jiffy.  Or you can implement your own gettimeoffset (probably based on 
-    some ad hoc hardware on your machine.)
-
   c) The following sub steps assume your CPU has counter register.
      Do you plan to use the CPU counter register as the timer interrupt
      or use an exnternal timer?
@@ -123,8 +107,8 @@ Step 3: implement rtc routines, board_time_init() and plat_timer_setup()
   board_time_init() -
         a) (optional) set up RTC routines,
         b) (optional) calibrate and set the mips_hpt_frequency
-            (only needed if you intended to use fixed_rate_gettimeoffset
-             or use cpu counter as timer interrupt source)
+            (only needed if you intended to use cpu counter as timer interrupt
+             source)
 
   plat_timer_setup() -
         a) (optional) over-write any choices made above by time_init().
@@ -154,8 +138,8 @@ for some of the functions in time.c.
 For example, you may define your own timer interrupt routine, which does
 some of its own processing and then calls timer_interrupt().
 
-You can also over-ride any of the built-in functions (gettimeoffset,
-RTC routines and/or timer interrupt routine).
+You can also over-ride any of the built-in functions (RTC routines
+and/or timer interrupt routine).
 
 
 PORTING NOTES FOR SMP
@@ -187,10 +171,3 @@ You need to decide on your timer interrupt sources.
 
         You can also do the low-level version of those interrupt routines,
         following similar dispatching routes described above.
-
-Note about do_gettimeoffset():
-
-  It is very likely the CPU counter registers are not sync'ed up in a SMP box.
-  Therefore you cannot really use the many of the existing routines that
-  are based on CPU counter.  You should wirte your own gettimeoffset rouinte
-  if you want intra-jiffy resolution.
diff --git a/arch/mips/au1000/common/time.c b/arch/mips/au1000/common/time.c
index 6768638883ea..fa1c62f05515 100644
--- a/arch/mips/au1000/common/time.c
+++ b/arch/mips/au1000/common/time.c
@@ -53,9 +53,6 @@ static unsigned long r4k_cur;    /* What counter should be at next timer irq */
 int     no_au1xxx_32khz;
 extern int allow_au1k_wait; /* default off for CP0 Counter */
 
-/* Cycle counter value at the previous timer interrupt.. */
-static unsigned int timerhi = 0, timerlo = 0;
-
 #ifdef CONFIG_PM
 #if HZ < 100 || HZ > 1000
 #error "unsupported HZ value! Must be in [100,1000]"
@@ -90,10 +87,6 @@ void mips_timer_interrupt(void)
                 goto null;
 
         do {
-                count = read_c0_count();
-                timerhi += (count < timerlo);   /* Wrap around */
-                timerlo = count;
-
                 kstat_this_cpu.irqs[irq]++;
                 do_timer(1);
 #ifndef CONFIG_SMP
@@ -297,88 +290,6 @@ unsigned long cal_r4koff(void)
         return (cpu_speed / HZ);
 }
 
-/* This is for machines which generate the exact clock. */
-#define USECS_PER_JIFFY (1000000/HZ)
-#define USECS_PER_JIFFY_FRAC (0x100000000LL*1000000/HZ&0xffffffff)
-
-static unsigned long
-div64_32(unsigned long v1, unsigned long v2, unsigned long v3)
-{
-        unsigned long r0;
-        do_div64_32(r0, v1, v2, v3);
-        return r0;
-}
-
-static unsigned long do_fast_cp0_gettimeoffset(void)
-{
-        u32 count;
-        unsigned long res, tmp;
-        unsigned long r0;
-
-        /* Last jiffy when do_fast_gettimeoffset() was called. */
-        static unsigned long last_jiffies=0;
-        unsigned long quotient;
-
-        /*
-         * Cached "1/(clocks per usec)*2^32" value.
-         * It has to be recalculated once each jiffy.
-         */
-        static unsigned long cached_quotient=0;
-
-        tmp = jiffies;
-
-        quotient = cached_quotient;
-
-        if (tmp && last_jiffies != tmp) {
-                last_jiffies = tmp;
-                if (last_jiffies != 0) {
-                        r0 = div64_32(timerhi, timerlo, tmp);
-                        quotient = div64_32(USECS_PER_JIFFY, USECS_PER_JIFFY_FRAC, r0);
-                        cached_quotient = quotient;
-                }
-        }
-
-        /* Get last timer tick in absolute kernel time */
-        count = read_c0_count();
-
-        /* .. relative to previous jiffy (32 bits is enough) */
-        count -= timerlo;
-
-        __asm__("multu\t%1,%2\n\t"
-                "mfhi\t%0"
-                : "=r" (res)
-                : "r" (count), "r" (quotient)
-                : "hi", "lo", GCC_REG_ACCUM);
-
-        /*
-         * Due to possible jiffies inconsistencies, we need to check
-         * the result so that we'll get a timer that is monotonic.
-         */
-        if (res >= USECS_PER_JIFFY)
-                res = USECS_PER_JIFFY-1;
-
-        return res;
-}
-
-#ifdef CONFIG_PM
-static unsigned long do_fast_pm_gettimeoffset(void)
-{
-        unsigned long pc0;
-        unsigned long offset;
-
-        pc0 = au_readl(SYS_TOYREAD);
-        au_sync();
-        offset = pc0 - last_pc0;
-        if (offset > 2*MATCH20_INC) {
-                printk("huge offset %x, last_pc0 %x last_match20 %x pc0 %x\n",
-                                (unsigned)offset, (unsigned)last_pc0,
-                                (unsigned)last_match20, (unsigned)pc0);
-        }
-        offset = (unsigned long)((offset * 305) / 10);
-        return offset;
-}
-#endif
-
 void __init plat_timer_setup(struct irqaction *irq)
 {
         unsigned int est_freq;
@@ -416,7 +327,6 @@ void __init plat_timer_setup(struct irqaction *irq)
                 unsigned int c0_status;
 
                 printk("WARNING: no 32KHz clock found.\n");
-                do_gettimeoffset = do_fast_cp0_gettimeoffset;
 
                 /* Ensure we get CPO_COUNTER interrupts.
                 */
@@ -441,19 +351,11 @@ void __init plat_timer_setup(struct irqaction *irq)
                 while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_M20);
                 startup_match20_interrupt(counter0_irq);
 
-                do_gettimeoffset = do_fast_pm_gettimeoffset;
-
                 /* We can use the real 'wait' instruction.
                 */
                 allow_au1k_wait = 1;
         }
 
-#else
-        /* We have to do this here instead of in timer_init because
-         * the generic code in arch/mips/kernel/time.c will write
-         * over our function pointer.
-         */
-        do_gettimeoffset = do_fast_cp0_gettimeoffset;
 #endif
 }
 
diff --git a/arch/mips/dec/time.c b/arch/mips/dec/time.c
index 4cf0c06e2414..69e424e9ab6f 100644
--- a/arch/mips/dec/time.c
+++ b/arch/mips/dec/time.c
@@ -160,11 +160,6 @@ static unsigned int dec_ioasic_hpt_read(void)
         return ioasic_read(IO_REG_FCTR);
 }
 
-static void dec_ioasic_hpt_init(unsigned int count)
-{
-        ioasic_write(IO_REG_FCTR, ioasic_read(IO_REG_FCTR) - count);
-}
-
 
 void __init dec_time_init(void)
 {
@@ -174,11 +169,9 @@ void __init dec_time_init(void)
         mips_timer_state = dec_timer_state;
         mips_timer_ack = dec_timer_ack;
 
-        if (!cpu_has_counter && IOASIC) {
+        if (!cpu_has_counter && IOASIC)
                 /* For pre-R4k systems we use the I/O ASIC's counter.  */
                 mips_hpt_read = dec_ioasic_hpt_read;
-                mips_hpt_init = dec_ioasic_hpt_init;
-        }
 
         /* Set up the rate of periodic DS1287 interrupts.  */
         CMOS_WRITE(RTC_REF_CLCK_32KHZ | (16 - __ffs(HZ)), RTC_REG_A);
diff --git a/arch/mips/jmr3927/rbhma3100/setup.c b/arch/mips/jmr3927/rbhma3100/setup.c
index 025434054ed0..16e5dfe7aa8a 100644
--- a/arch/mips/jmr3927/rbhma3100/setup.c
+++ b/arch/mips/jmr3927/rbhma3100/setup.c
@@ -170,12 +170,20 @@ static void jmr3927_machine_power_off(void)
         while (1);
 }
 
+static unsigned int jmr3927_hpt_read(void)
+{
+        /* We assume this function is called xtime_lock held. */
+        return jiffies * (JMR3927_TIMER_CLK / HZ) + jmr3927_tmrptr->trr;
+}
+
 #define USE_RTC_DS1742
 #ifdef USE_RTC_DS1742
 extern void rtc_ds1742_init(unsigned long base);
 #endif
 static void __init jmr3927_time_init(void)
 {
+        mips_hpt_read = jmr3927_hpt_read;
+        mips_hpt_frequency = JMR3927_TIMER_CLK;
 #ifdef USE_RTC_DS1742
         if (jmr3927_have_nvram()) {
                 rtc_ds1742_init(JMR3927_IOC_NVRAMB_ADDR);
@@ -183,12 +191,8 @@ static void __init jmr3927_time_init(void)
 #endif
 }
 
-unsigned long jmr3927_do_gettimeoffset(void);
-
 void __init plat_timer_setup(struct irqaction *irq)
 {
-        do_gettimeoffset = jmr3927_do_gettimeoffset;
-
         jmr3927_tmrptr->cpra = JMR3927_TIMER_CLK / HZ;
         jmr3927_tmrptr->itmr = TXx927_TMTITMR_TIIE | TXx927_TMTITMR_TZCE;
         jmr3927_tmrptr->ccdr = JMR3927_TIMER_CCD;
@@ -200,34 +204,6 @@ void __init plat_timer_setup(struct irqaction *irq)
 
 #define USECS_PER_JIFFY (1000000/HZ)
 
-unsigned long jmr3927_do_gettimeoffset(void)
-{
-       unsigned long count;
-       unsigned long res = 0;
-
-       /* MUST read TRR before TISR. */
-       count = jmr3927_tmrptr->trr;
-
-       if (jmr3927_tmrptr->tisr & TXx927_TMTISR_TIIS) {
-               /* timer interrupt is pending.  use Max value. */
-               res = USECS_PER_JIFFY - 1;
-       } else {
-               /* convert to usec */
-               /* res = count / (JMR3927_TIMER_CLK / 1000000); */
-               res = (count << 7) / ((JMR3927_TIMER_CLK << 7) / 1000000);
-
-               /*
-                * Due to possible jiffies inconsistencies, we need to check
-                * the result so that we'll get a timer that is monotonic.
-                */
-               if (res >= USECS_PER_JIFFY)
-                       res = USECS_PER_JIFFY-1;
-       }
-
-       return res;
-}
-
-
 //#undef DO_WRITE_THROUGH
 #define DO_WRITE_THROUGH
 #define DO_ENABLE_CACHE
diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
index debe86c2f691..e535f86efa2f 100644
--- a/arch/mips/kernel/time.c
+++ b/arch/mips/kernel/time.c
@@ -11,6 +11,7 @@
  * Free Software Foundation;  either version 2 of the  License, or (at your
  * option) any later version.
  */
+#include <linux/clocksource.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
@@ -67,15 +68,9 @@ int (*rtc_mips_set_time)(unsigned long) = null_rtc_set_time;
 int (*rtc_mips_set_mmss)(unsigned long);
 
 
-/* usecs per counter cycle, shifted to left by 32 bits */
-static unsigned int sll32_usecs_per_cycle;
-
 /* how many counter cycles in a jiffy */
 static unsigned long cycles_per_jiffy __read_mostly;
 
-/* Cycle counter value at the previous timer interrupt.. */
-static unsigned int timerhi, timerlo;
-
 /* expirelo is the count value for next CPU timer interrupt */
 static unsigned int expirelo;
 
@@ -93,7 +88,7 @@ static unsigned int null_hpt_read(void)
         return 0;
 }
 
-static void null_hpt_init(unsigned int count)
+static void __init null_hpt_init(void)
 {
         /* nothing */
 }
@@ -128,186 +123,18 @@ static unsigned int c0_hpt_read(void)
         return read_c0_count();
 }
 
-/* For use solely as a high precision timer.  */
-static void c0_hpt_init(unsigned int count)
-{
-        write_c0_count(read_c0_count() - count);
-}
-
 /* For use both as a high precision timer and an interrupt source.  */
-static void c0_hpt_timer_init(unsigned int count)
+static void __init c0_hpt_timer_init(void)
 {
-        count = read_c0_count() - count;
-        expirelo = (count / cycles_per_jiffy + 1) * cycles_per_jiffy;
-        write_c0_count(expirelo - cycles_per_jiffy);
+        expirelo = read_c0_count() + cycles_per_jiffy;
         write_c0_compare(expirelo);
-        write_c0_count(count);
 }
 
 int (*mips_timer_state)(void);
 void (*mips_timer_ack)(void);
 unsigned int (*mips_hpt_read)(void);
-void (*mips_hpt_init)(unsigned int);
-
-/*
- * Gettimeoffset routines.  These routines returns the time duration
- * since last timer interrupt in usecs.
- *
- * If the exact CPU counter frequency is known, use fixed_rate_gettimeoffset.
- * Otherwise use calibrate_gettimeoffset()
- *
- * If the CPU does not have the counter register, you can either supply
- * your own gettimeoffset() routine, or use null_gettimeoffset(), which
- * gives the same resolution as HZ.
- */
-
-static unsigned long null_gettimeoffset(void)
-{
-        return 0;
-}
-
-
-/* The function pointer to one of the gettimeoffset funcs.  */
-unsigned long (*do_gettimeoffset)(void) = null_gettimeoffset;
-
-
-static unsigned long fixed_rate_gettimeoffset(void)
-{
-        u32 count;
-        unsigned long res;
-
-        /* Get last timer tick in absolute kernel time */
-        count = mips_hpt_read();
-
-        /* .. relative to previous jiffy (32 bits is enough) */
-        count -= timerlo;
-
-        __asm__("multu  %1,%2"
-                : "=h" (res)
-                : "r" (count), "r" (sll32_usecs_per_cycle)
-                : "lo", GCC_REG_ACCUM);
-
-        /*
-         * Due to possible jiffies inconsistencies, we need to check
-         * the result so that we'll get a timer that is monotonic.
-         */
-        if (res >= USECS_PER_JIFFY)
-                res = USECS_PER_JIFFY - 1;
-
-        return res;
-}
-
-
-/*
- * Cached "1/(clocks per usec) * 2^32" value.
- * It has to be recalculated once each jiffy.
- */
-static unsigned long cached_quotient;
-
-/* Last jiffy when calibrate_divXX_gettimeoffset() was called. */
-static unsigned long last_jiffies;
-
-/*
- * This is moved from dec/time.c:do_ioasic_gettimeoffset() by Maciej.
- */
-static unsigned long calibrate_div32_gettimeoffset(void)
-{
-        u32 count;
-        unsigned long res, tmp;
-        unsigned long quotient;
-
-        tmp = jiffies;
-
-        quotient = cached_quotient;
-
-        if (last_jiffies != tmp) {
-                last_jiffies = tmp;
-                if (last_jiffies != 0) {
-                        unsigned long r0;
-                        do_div64_32(r0, timerhi, timerlo, tmp);
-                        do_div64_32(quotient, USECS_PER_JIFFY,
-                                    USECS_PER_JIFFY_FRAC, r0);
-                        cached_quotient = quotient;
-                }
-        }
-
-        /* Get last timer tick in absolute kernel time */
-        count = mips_hpt_read();
-
-        /* .. relative to previous jiffy (32 bits is enough) */
-        count -= timerlo;
-
-        __asm__("multu  %1,%2"
-                : "=h" (res)
-                : "r" (count), "r" (quotient)
-                : "lo", GCC_REG_ACCUM);
-
-        /*
-         * Due to possible jiffies inconsistencies, we need to check
-         * the result so that we'll get a timer that is monotonic.
-         */
-        if (res >= USECS_PER_JIFFY)
-                res = USECS_PER_JIFFY - 1;
-
-        return res;
-}
-
-static unsigned long calibrate_div64_gettimeoffset(void)
-{
-        u32 count;
-        unsigned long res, tmp;
-        unsigned long quotient;
-
-        tmp = jiffies;
-
-        quotient = cached_quotient;
-
-        if (last_jiffies != tmp) {
-                last_jiffies = tmp;
-                if (last_jiffies) {
-                        unsigned long r0;
-                        __asm__(".set   push\n\t"
-                                ".set   mips3\n\t"
-                                "lwu    %0,%3\n\t"
-                                "dsll32 %1,%2,0\n\t"
-                                "or     %1,%1,%0\n\t"
-                                "ddivu  $0,%1,%4\n\t"
-                                "mflo   %1\n\t"
-                                "dsll32 %0,%5,0\n\t"
-                                "or     %0,%0,%6\n\t"
-                                "ddivu  $0,%0,%1\n\t"
-                                "mflo   %0\n\t"
-                                ".set   pop"
-                                : "=&r" (quotient), "=&r" (r0)
-                                : "r" (timerhi), "m" (timerlo),
-                                  "r" (tmp), "r" (USECS_PER_JIFFY),
-                                  "r" (USECS_PER_JIFFY_FRAC)
-                                : "hi", "lo", GCC_REG_ACCUM);
-                        cached_quotient = quotient;
-                }
-        }
-
-        /* Get last timer tick in absolute kernel time */
-        count = mips_hpt_read();
-
-        /* .. relative to previous jiffy (32 bits is enough) */
-        count -= timerlo;
-
-        __asm__("multu  %1,%2"
-                : "=h" (res)
-                : "r" (count), "r" (quotient)
-                : "lo", GCC_REG_ACCUM);
-
-        /*
-         * Due to possible jiffies inconsistencies, we need to check
-         * the result so that we'll get a timer that is monotonic.
-         */
-        if (res >= USECS_PER_JIFFY)
-                res = USECS_PER_JIFFY - 1;
-
-        return res;
-}
-
+void (*mips_hpt_init)(void) __initdata = null_hpt_init;
+unsigned int mips_hpt_mask = 0xffffffff;
 
 /* last time when xtime and rtc are sync'ed up */
 static long last_rtc_update;
@@ -334,18 +161,10 @@ void local_timer_interrupt(int irq, void *dev_id)
  */
 irqreturn_t timer_interrupt(int irq, void *dev_id)
 {
-        unsigned long j;
-        unsigned int count;
-
         write_seqlock(&xtime_lock);
 
-        count = mips_hpt_read();
         mips_timer_ack();
 
-        /* Update timerhi/timerlo for intra-jiffy calibration. */
-        timerhi += count < timerlo;                     /* Wrap around */
-        timerlo = count;
-
         /*
          * call the generic timer interrupt handling
          */
@@ -368,47 +187,6 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
                 }
         }
 
-        /*
-         * If jiffies has overflown in this timer_interrupt, we must
-         * update the timer[hi]/[lo] to make fast gettimeoffset funcs
-         * quotient calc still valid. -arca
-         *
-         * The first timer interrupt comes late as interrupts are
-         * enabled long after timers are initialized.  Therefore the
-         * high precision timer is fast, leading to wrong gettimeoffset()
-         * calculations.  We deal with it by setting it based on the
-         * number of its ticks between the second and the third interrupt.
-         * That is still somewhat imprecise, but it's a good estimate.
-         * --macro
-         */
-        j = jiffies;
-        if (j < 4) {
-                static unsigned int prev_count;
-                static int hpt_initialized;
-
-                switch (j) {
-                case 0:
-                        timerhi = timerlo = 0;
-                        mips_hpt_init(count);
-                        break;
-                case 2:
-                        prev_count = count;
-                        break;
-                case 3:
-                        if (!hpt_initialized) {
-                                unsigned int c3 = 3 * (count - prev_count);
-
-                                timerhi = 0;
-                                timerlo = c3;
-                                mips_hpt_init(count - c3);
-                                hpt_initialized = 1;
-                        }
-                        break;
-                default:
-                        break;
-                }
-        }
-
         write_sequnlock(&xtime_lock);
 
         /*
@@ -476,12 +254,11 @@ asmlinkage void ll_local_timer_interrupt(int irq)
  * 1) board_time_init() -
  *      a) (optional) set up RTC routines,
  *      b) (optional) calibrate and set the mips_hpt_frequency
- *          (only needed if you intended to use fixed_rate_gettimeoffset
- *           or use cpu counter as timer interrupt source)
+ *          (only needed if you intended to use cpu counter as timer interrupt
+ *           source)
  * 2) setup xtime based on rtc_mips_get_time().
- * 3) choose a appropriate gettimeoffset routine.
- * 4) calculate a couple of cached variables for later usage
- * 5) plat_timer_setup() -
+ * 3) calculate a couple of cached variables for later usage
+ * 4) plat_timer_setup() -
  *      a) (optional) over-write any choices made above by time_init().
  *      b) machine specific code should setup the timer irqaction.
  *      c) enable the timer interrupt
@@ -533,13 +310,48 @@ static unsigned int __init calibrate_hpt(void)
         } while (--i);
         hpt_end = mips_hpt_read();
 
-        hpt_count = hpt_end - hpt_start;
+        hpt_count = (hpt_end - hpt_start) & mips_hpt_mask;
         hz = HZ;
         frequency = (u64)hpt_count * (u64)hz;
 
         return frequency >> log_2_loops;
 }
 
+static cycle_t read_mips_hpt(void)
+{
+        return (cycle_t)mips_hpt_read();
+}
+
+static struct clocksource clocksource_mips = {
+        .name           = "MIPS",
+        .read           = read_mips_hpt,
+        .is_continuous  = 1,
+};
+
+static void __init init_mips_clocksource(void)
+{
+        u64 temp;
+        u32 shift;
+
+        if (!mips_hpt_frequency || mips_hpt_read == null_hpt_read)
+                return;
+
+        /* Calclate a somewhat reasonable rating value */
+        clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
+        /* Find a shift value */
+        for (shift = 32; shift > 0; shift--) {
+                temp = (u64) NSEC_PER_SEC << shift;
+                do_div(temp, mips_hpt_frequency);
+                if ((temp >> 32) == 0)
+                        break;
+        }
+        clocksource_mips.shift = shift;
+        clocksource_mips.mult = (u32)temp;
+        clocksource_mips.mask = mips_hpt_mask;
+
+        clocksource_register(&clocksource_mips);
+}
+
 void __init time_init(void)
 {
         if (board_time_init)
@@ -555,41 +367,21 @@ void __init time_init(void)
                                 -xtime.tv_sec, -xtime.tv_nsec);
 
         /* Choose appropriate high precision timer routines.  */
-        if (!cpu_has_counter && !mips_hpt_read) {
+        if (!cpu_has_counter && !mips_hpt_read)
                 /* No high precision timer -- sorry.  */
                 mips_hpt_read = null_hpt_read;
-                mips_hpt_init = null_hpt_init;
-        } else if (!mips_hpt_frequency && !mips_timer_state) {
+        else if (!mips_hpt_frequency && !mips_timer_state) {
                 /* A high precision timer of unknown frequency.  */
-                if (!mips_hpt_read) {
+                if (!mips_hpt_read)
                         /* No external high precision timer -- use R4k.  */
                         mips_hpt_read = c0_hpt_read;
-                        mips_hpt_init = c0_hpt_init;
-                }
-
-                if (cpu_has_mips32r1 || cpu_has_mips32r2 ||
-                    (current_cpu_data.isa_level == MIPS_CPU_ISA_I) ||
-                    (current_cpu_data.isa_level == MIPS_CPU_ISA_II))
-                        /*
-                         * We need to calibrate the counter but we don't have
-                         * 64-bit division.
-                         */
-                        do_gettimeoffset = calibrate_div32_gettimeoffset;
-                else
-                        /*
-                         * We need to calibrate the counter but we *do* have
-                         * 64-bit division.
-                         */
-                        do_gettimeoffset = calibrate_div64_gettimeoffset;
         } else {
                 /* We know counter frequency.  Or we can get it.  */
                 if (!mips_hpt_read) {
                         /* No external high precision timer -- use R4k.  */
                         mips_hpt_read = c0_hpt_read;
 
-                        if (mips_timer_state)
-                                mips_hpt_init = c0_hpt_init;
-                        else {
+                        if (!mips_timer_state) {
                                 /* No external timer interrupt -- use R4k.  */
                                 mips_hpt_init = c0_hpt_timer_init;
                                 mips_timer_ack = c0_timer_ack;
@@ -598,16 +390,9 @@ void __init time_init(void)
                 if (!mips_hpt_frequency)
                         mips_hpt_frequency = calibrate_hpt();
 
-                do_gettimeoffset = fixed_rate_gettimeoffset;
-
                 /* Calculate cache parameters.  */
                 cycles_per_jiffy = (mips_hpt_frequency + HZ / 2) / HZ;
 
-                /* sll32_usecs_per_cycle = 10^6 * 2^32 / mips_counter_freq  */
-                do_div64_32(sll32_usecs_per_cycle,
-                            1000000, mips_hpt_frequency / 2,
-                            mips_hpt_frequency);
-
                 /* Report the high precision timer rate for a reference.  */
                 printk("Using %u.%03u MHz high precision timer.\n",
                        ((mips_hpt_frequency + 500) / 1000) / 1000,
@@ -619,7 +404,7 @@ void __init time_init(void)
                 mips_timer_ack = null_timer_ack;
 
         /* This sets up the high precision timer for the first interrupt.  */
-        mips_hpt_init(mips_hpt_read());
+        mips_hpt_init();
 
         /*
          * Call board specific timer interrupt setup.
@@ -633,6 +418,8 @@ void __init time_init(void)
          * is not invoked accidentally.
          */
         plat_timer_setup(&timer_irqaction);
+
+        init_mips_clocksource();
 }
 
 #define FEBRUARY                2
diff --git a/arch/mips/philips/pnx8550/common/time.c b/arch/mips/philips/pnx8550/common/time.c
index 0af655b1f330..65c440e8480b 100644
--- a/arch/mips/philips/pnx8550/common/time.c
+++ b/arch/mips/philips/pnx8550/common/time.c
@@ -41,8 +41,8 @@ extern unsigned int mips_hpt_frequency;
  * 1) board_time_init() -
  *      a) (optional) set up RTC routines,
  *      b) (optional) calibrate and set the mips_hpt_frequency
- *          (only needed if you intended to use fixed_rate_gettimeoffset
- *           or use cpu counter as timer interrupt source)
+ *          (only needed if you intended to use cpu counter as timer interrupt
+ *           source)
  */
 
 void pnx8550_time_init(void)
diff --git a/arch/mips/pmc-sierra/yosemite/smp.c b/arch/mips/pmc-sierra/yosemite/smp.c
index 65fa3a23ea5e..3cc0436db6cf 100644
--- a/arch/mips/pmc-sierra/yosemite/smp.c
+++ b/arch/mips/pmc-sierra/yosemite/smp.c
@@ -3,9 +3,7 @@
 
 #include <asm/pmon.h>
 #include <asm/titan_dep.h>
-
-extern unsigned int (*mips_hpt_read)(void);
-extern void (*mips_hpt_init)(unsigned int);
+#include <asm/time.h>
 
 #define LAUNCHSTACK_SIZE 256
 
@@ -101,7 +99,7 @@ void prom_cpus_done(void)
  */
 void prom_init_secondary(void)
 {
-        mips_hpt_init(mips_hpt_read());
+        mips_hpt_init();
 
         set_c0_status(ST0_CO | ST0_IE | ST0_IM);
 }
diff --git a/arch/mips/sgi-ip27/ip27-timer.c b/arch/mips/sgi-ip27/ip27-timer.c
index 4e870fc4469b..c965705f3427 100644
--- a/arch/mips/sgi-ip27/ip27-timer.c
+++ b/arch/mips/sgi-ip27/ip27-timer.c
@@ -134,13 +134,6 @@ again:
         irq_exit();
 }
 
-unsigned long ip27_do_gettimeoffset(void)
-{
-        unsigned long ct_cur1;
-        ct_cur1 = REMOTE_HUB_L(cputonasid(0), PI_RT_COUNT) + CYCLES_PER_JIFFY;
-        return (ct_cur1 - ct_cur[0]) * NSEC_PER_CYCLE / 1000;
-}
-
 /* Includes for ioc3_init().  */
 #include <asm/sn/types.h>
 #include <asm/sn/sn0/addrs.h>
@@ -248,12 +241,17 @@ void __init plat_timer_setup(struct irqaction *irq)
         setup_irq(irqno, &rt_irqaction);
 }
 
+static unsigned int ip27_hpt_read(void)
+{
+        return REMOTE_HUB_L(cputonasid(0), PI_RT_COUNT);
+}
+
 void __init ip27_time_init(void)
 {
+        mips_hpt_read = ip27_hpt_read;
+        mips_hpt_frequency = CYCLES_PER_SEC;
         xtime.tv_sec = get_m48t35_time();
         xtime.tv_nsec = 0;
-
-        do_gettimeoffset = ip27_do_gettimeoffset;
 }
 
 void __init cpu_time_init(void)
diff --git a/arch/mips/sibyte/bcm1480/time.c b/arch/mips/sibyte/bcm1480/time.c
index bf12af46132e..e136bde5248e 100644
--- a/arch/mips/sibyte/bcm1480/time.c
+++ b/arch/mips/sibyte/bcm1480/time.c
@@ -47,6 +47,12 @@
 #define IMR_IP3_VAL     K_BCM1480_INT_MAP_I1
 #define IMR_IP4_VAL     K_BCM1480_INT_MAP_I2
 
+#ifdef CONFIG_SIMULATION
+#define BCM1480_HPT_VALUE       50000
+#else
+#define BCM1480_HPT_VALUE       1000000
+#endif
+
 extern int bcm1480_steal_irq(int irq);
 
 void bcm1480_time_init(void)
@@ -59,11 +65,6 @@ void bcm1480_time_init(void)
                 BUG();
         }
 
-        if (!cpu) {
-                /* Use our own gettimeoffset() routine */
-                do_gettimeoffset = bcm1480_gettimeoffset;
-        }
-
         bcm1480_mask_irq(cpu, irq);
 
         /* Map the timer interrupt to ip[4] of this cpu */
@@ -74,11 +75,7 @@ void bcm1480_time_init(void)
         /* Disable the timer and set up the count */
         __raw_writeq(0, IOADDR(A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG)));
         __raw_writeq(
-#ifndef CONFIG_SIMULATION
-                1000000/HZ
-#else
-                50000/HZ
-#endif
+                BCM1480_HPT_VALUE/HZ
                 , IOADDR(A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_INIT)));
 
         /* Set the timer running */
@@ -122,16 +119,16 @@ void bcm1480_timer_interrupt(void)
         }
 }
 
-/*
- * We use our own do_gettimeoffset() instead of the generic one,
- * because the generic one does not work for SMP case.
- * In addition, since we use general timer 0 for system time,
- * we can get accurate intra-jiffy offset without calibration.
- */
-unsigned long bcm1480_gettimeoffset(void)
+static unsigned int bcm1480_hpt_read(void)
 {
+        /* We assume this function is called xtime_lock held. */
         unsigned long count =
                 __raw_readq(IOADDR(A_SCD_TIMER_REGISTER(0, R_SCD_TIMER_CNT)));
+        return (jiffies + 1) * (BCM1480_HPT_VALUE / HZ) - count;
+}
 
-        return 1000000/HZ - count;
+void __init bcm1480_hpt_setup(void)
+{
+        mips_hpt_read = bcm1480_hpt_read;
+        mips_hpt_frequency = BCM1480_HPT_VALUE;
 }
diff --git a/arch/mips/sibyte/sb1250/time.c b/arch/mips/sibyte/sb1250/time.c
index 0ccf1796dd78..bcb74f2c1948 100644
--- a/arch/mips/sibyte/sb1250/time.c
+++ b/arch/mips/sibyte/sb1250/time.c
@@ -47,15 +47,11 @@
 
 #define SB1250_HPT_NUM          3
 #define SB1250_HPT_VALUE        M_SCD_TIMER_CNT /* max value */
-#define SB1250_HPT_SHIFT        ((sizeof(unsigned int)*8)-V_SCD_TIMER_WIDTH)
 
 
 extern int sb1250_steal_irq(int irq);
 
 static unsigned int sb1250_hpt_read(void);
-static void sb1250_hpt_init(unsigned int);
-
-static unsigned int hpt_offset;
 
 void __init sb1250_hpt_setup(void)
 {
@@ -69,13 +65,9 @@ void __init sb1250_hpt_setup(void)
                 __raw_writeq(M_SCD_TIMER_ENABLE | M_SCD_TIMER_MODE_CONTINUOUS,
                              IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CFG)));
 
-                /*
-                 * we need to fill 32 bits, so just use the upper 23 bits and pretend
-                 * the timer is going 512Mhz instead of 1Mhz
-                 */
-                mips_hpt_frequency = V_SCD_TIMER_FREQ << SB1250_HPT_SHIFT;
-                mips_hpt_init = sb1250_hpt_init;
+                mips_hpt_frequency = V_SCD_TIMER_FREQ;
                 mips_hpt_read = sb1250_hpt_read;
+                mips_hpt_mask = M_SCD_TIMER_INIT;
         }
 }
 
@@ -149,11 +141,7 @@ void sb1250_timer_interrupt(void)
 
 /*
  * The HPT is free running from SB1250_HPT_VALUE down to 0 then starts over
- * again. There's no easy way to set to a specific value so store init value
- * in hpt_offset and subtract each time.
- *
- * Note: Timer isn't full 32bits so shift it into the upper part making
- *       it appear to run at a higher frequency.
+ * again.
  */
 static unsigned int sb1250_hpt_read(void)
 {
@@ -161,13 +149,5 @@ static unsigned int sb1250_hpt_read(void)
 
         count = G_SCD_TIMER_CNT(__raw_readq(IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CNT))));
 
-        count = (SB1250_HPT_VALUE - count) << SB1250_HPT_SHIFT;
-
-        return count - hpt_offset;
-}
-
-static void sb1250_hpt_init(unsigned int count)
-{
-        hpt_offset = count;
-        return;
+        return SB1250_HPT_VALUE - count;
 }
diff --git a/include/asm-mips/div64.h b/include/asm-mips/div64.h
index 5f7dcf5452e7..d107832de1b6 100644
--- a/include/asm-mips/div64.h
+++ b/include/asm-mips/div64.h
@@ -83,27 +83,6 @@
 #if (_MIPS_SZLONG == 64)
 
 /*
- * Don't use this one in new code
- */
-#define do_div64_32(res, high, low, base) ({ \
-        unsigned int __quot, __mod; \
-        unsigned long __div; \
-        unsigned int __low, __high, __base; \
-        \
-        __high = (high); \
-        __low = (low); \
-        __div = __high; \
-        __div = __div << 32 | __low; \
-        __base = (base); \
-        \
-        __mod = __div % __base; \
-        __div = __div / __base; \
-        \
-        __quot = __div; \
-        (res) = __quot; \
-        __mod; })
-
-/*
  * Hey, we're already 64-bit, no
  * need to play games..
  */
diff --git a/include/asm-mips/sibyte/sb1250.h b/include/asm-mips/sibyte/sb1250.h
index b09e16c93ca0..2ba6988ddc8e 100644
--- a/include/asm-mips/sibyte/sb1250.h
+++ b/include/asm-mips/sibyte/sb1250.h
@@ -51,8 +51,8 @@ extern void sb1250_mask_irq(int cpu, int irq);
 extern void sb1250_unmask_irq(int cpu, int irq);
 extern void sb1250_smp_finish(void);
 
+extern void bcm1480_hpt_setup(void);
 extern void bcm1480_time_init(void);
-extern unsigned long bcm1480_gettimeoffset(void);
 extern void bcm1480_mask_irq(int cpu, int irq);
 extern void bcm1480_unmask_irq(int cpu, int irq);
 extern void bcm1480_smp_finish(void);
diff --git a/include/asm-mips/time.h b/include/asm-mips/time.h
index 28512ba2266e..625acd337bc3 100644
--- a/include/asm-mips/time.h
+++ b/include/asm-mips/time.h
@@ -48,7 +48,8 @@ extern void (*mips_timer_ack)(void);
  * If mips_hpt_read is NULL, an R4k-compatible timer setup is attempted.
  */
 extern unsigned int (*mips_hpt_read)(void);
-extern void (*mips_hpt_init)(unsigned int);
+extern void (*mips_hpt_init)(void);
+extern unsigned int mips_hpt_mask;
 
 /*
  * to_tm() converts system time back to (year, mon, day, hour, min, sec).
@@ -58,13 +59,6 @@ extern void (*mips_hpt_init)(unsigned int);
 extern void to_tm(unsigned long tim, struct rtc_time *tm);
 
 /*
- * do_gettimeoffset(). By default, this func pointer points to
- * do_null_gettimeoffset(), which leads to the same resolution as HZ.
- * Higher resolution versions are available, which give ~1us resolution.
- */
-extern unsigned long (*do_gettimeoffset)(void);
-
-/*
  * high-level timer interrupt routines.
  */
 extern irqreturn_t timer_interrupt(int irq, void *dev_id);