[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>

1 files changed, 53 insertions, 266 deletions

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