[IA64] Convert to generic timekeeping/clocksource

This is a merge of Peter Keilty's initial patch (which was
revived by Bob Picco) for this with Hidetoshi Seto's fixes
and scaling improvements.

Acked-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

14 files changed, 286 insertions, 142 deletions

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 616c96e73483..36c7b9682aa6 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -62,7 +62,11 @@ config GENERIC_CALIBRATE_DELAY
         bool
         default y
 
-config TIME_INTERPOLATION
+config GENERIC_TIME
+        bool
+        default y
+
+config GENERIC_TIME_VSYSCALL
         bool
         default y
 
diff --git a/arch/ia64/configs/bigsur_defconfig b/arch/ia64/configs/bigsur_defconfig
index 90e9c2e61bf4..9eb48c0927b0 100644
--- a/arch/ia64/configs/bigsur_defconfig
+++ b/arch/ia64/configs/bigsur_defconfig
@@ -85,7 +85,7 @@ CONFIG_MMU=y
 CONFIG_SWIOTLB=y
 CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
-CONFIG_TIME_INTERPOLATION=y
+CONFIG_GENERIC_TIME=y
 CONFIG_EFI=y
 CONFIG_GENERIC_IOMAP=y
 CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER=y
diff --git a/arch/ia64/configs/gensparse_defconfig b/arch/ia64/configs/gensparse_defconfig
index 0d29aa2066b3..3a9ed951db08 100644
--- a/arch/ia64/configs/gensparse_defconfig
+++ b/arch/ia64/configs/gensparse_defconfig
@@ -86,7 +86,7 @@ CONFIG_MMU=y
 CONFIG_SWIOTLB=y
 CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
-CONFIG_TIME_INTERPOLATION=y
+CONFIG_GENERIC_TIME=y
 CONFIG_EFI=y
 CONFIG_GENERIC_IOMAP=y
 CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER=y
diff --git a/arch/ia64/configs/sim_defconfig b/arch/ia64/configs/sim_defconfig
index d9146c31ea13..c420d9f3df98 100644
--- a/arch/ia64/configs/sim_defconfig
+++ b/arch/ia64/configs/sim_defconfig
@@ -86,7 +86,7 @@ CONFIG_MMU=y
 CONFIG_SWIOTLB=y
 CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
-CONFIG_TIME_INTERPOLATION=y
+CONFIG_GENERIC_TIME=y
 CONFIG_EFI=y
 CONFIG_GENERIC_IOMAP=y
 CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER=y
diff --git a/arch/ia64/configs/sn2_defconfig b/arch/ia64/configs/sn2_defconfig
index 64e951de4e57..4c9ffc47bc7a 100644
--- a/arch/ia64/configs/sn2_defconfig
+++ b/arch/ia64/configs/sn2_defconfig
@@ -93,7 +93,7 @@ CONFIG_SWIOTLB=y
 CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 CONFIG_GENERIC_FIND_NEXT_BIT=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
-CONFIG_TIME_INTERPOLATION=y
+CONFIG_GENERIC_TIME=y
 CONFIG_DMI=y
 CONFIG_EFI=y
 CONFIG_GENERIC_IOMAP=y
diff --git a/arch/ia64/configs/tiger_defconfig b/arch/ia64/configs/tiger_defconfig
index a1446931b401..e208747d5de4 100644
--- a/arch/ia64/configs/tiger_defconfig
+++ b/arch/ia64/configs/tiger_defconfig
@@ -98,7 +98,7 @@ CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 # CONFIG_ARCH_HAS_ILOG2_U64 is not set
 CONFIG_GENERIC_FIND_NEXT_BIT=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
-CONFIG_TIME_INTERPOLATION=y
+CONFIG_GENERIC_TIME=y
 CONFIG_DMI=y
 CONFIG_EFI=y
 CONFIG_GENERIC_IOMAP=y
diff --git a/arch/ia64/configs/zx1_defconfig b/arch/ia64/configs/zx1_defconfig
index 1c7955c16358..4a060fc39934 100644
--- a/arch/ia64/configs/zx1_defconfig
+++ b/arch/ia64/configs/zx1_defconfig
@@ -96,7 +96,7 @@ CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 # CONFIG_ARCH_HAS_ILOG2_U64 is not set
 CONFIG_GENERIC_FIND_NEXT_BIT=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
-CONFIG_TIME_INTERPOLATION=y
+CONFIG_GENERIC_TIME=y
 CONFIG_DMI=y
 CONFIG_EFI=y
 CONFIG_GENERIC_IOMAP=y
diff --git a/arch/ia64/defconfig b/arch/ia64/defconfig
index 90bd9601cdde..461f8ee738fb 100644
--- a/arch/ia64/defconfig
+++ b/arch/ia64/defconfig
@@ -98,7 +98,7 @@ CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 # CONFIG_ARCH_HAS_ILOG2_U64 is not set
 CONFIG_GENERIC_FIND_NEXT_BIT=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
-CONFIG_TIME_INTERPOLATION=y
+CONFIG_GENERIC_TIME=y
 CONFIG_DMI=y
 CONFIG_EFI=y
 CONFIG_GENERIC_IOMAP=y
diff --git a/arch/ia64/kernel/asm-offsets.c b/arch/ia64/kernel/asm-offsets.c
index 2236fabbb3c6..0aebc6f79e95 100644
--- a/arch/ia64/kernel/asm-offsets.c
+++ b/arch/ia64/kernel/asm-offsets.c
@@ -7,6 +7,7 @@
 #define ASM_OFFSETS_C 1
 
 #include <linux/sched.h>
+#include <linux/clocksource.h>
 
 #include <asm-ia64/processor.h>
 #include <asm-ia64/ptrace.h>
@@ -15,6 +16,7 @@
 #include <asm-ia64/mca.h>
 
 #include "../kernel/sigframe.h"
+#include "../kernel/fsyscall_gtod_data.h"
 
 #define DEFINE(sym, val) \
         asm volatile("\n->" #sym " %0 " #val : : "i" (val))
@@ -256,17 +258,24 @@ void foo(void)
         BLANK();
 
         /* used by fsys_gettimeofday in arch/ia64/kernel/fsys.S */
-        DEFINE(IA64_TIME_INTERPOLATOR_ADDRESS_OFFSET, offsetof (struct time_interpolator, addr));
-        DEFINE(IA64_TIME_INTERPOLATOR_SOURCE_OFFSET, offsetof (struct time_interpolator, source));
-        DEFINE(IA64_TIME_INTERPOLATOR_SHIFT_OFFSET, offsetof (struct time_interpolator, shift));
-        DEFINE(IA64_TIME_INTERPOLATOR_NSEC_OFFSET, offsetof (struct time_interpolator, nsec_per_cyc));
-        DEFINE(IA64_TIME_INTERPOLATOR_OFFSET_OFFSET, offsetof (struct time_interpolator, offset));
-        DEFINE(IA64_TIME_INTERPOLATOR_LAST_CYCLE_OFFSET, offsetof (struct time_interpolator, last_cycle));
-        DEFINE(IA64_TIME_INTERPOLATOR_LAST_COUNTER_OFFSET, offsetof (struct time_interpolator, last_counter));
-        DEFINE(IA64_TIME_INTERPOLATOR_JITTER_OFFSET, offsetof (struct time_interpolator, jitter));
-        DEFINE(IA64_TIME_INTERPOLATOR_MASK_OFFSET, offsetof (struct time_interpolator, mask));
-        DEFINE(IA64_TIME_SOURCE_CPU, TIME_SOURCE_CPU);
-        DEFINE(IA64_TIME_SOURCE_MMIO64, TIME_SOURCE_MMIO64);
-        DEFINE(IA64_TIME_SOURCE_MMIO32, TIME_SOURCE_MMIO32);
-        DEFINE(IA64_TIMESPEC_TV_NSEC_OFFSET, offsetof (struct timespec, tv_nsec));
+        DEFINE(IA64_GTOD_LOCK_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, lock));
+        DEFINE(IA64_GTOD_WALL_TIME_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, wall_time));
+        DEFINE(IA64_GTOD_MONO_TIME_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, monotonic_time));
+        DEFINE(IA64_CLKSRC_MASK_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, clk_mask));
+        DEFINE(IA64_CLKSRC_MULT_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, clk_mult));
+        DEFINE(IA64_CLKSRC_SHIFT_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, clk_shift));
+        DEFINE(IA64_CLKSRC_MMIO_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, clk_fsys_mmio));
+        DEFINE(IA64_CLKSRC_CYCLE_LAST_OFFSET,
+                offsetof (struct fsyscall_gtod_data_t, clk_cycle_last));
+        DEFINE(IA64_ITC_JITTER_OFFSET,
+                offsetof (struct itc_jitter_data_t, itc_jitter));
+        DEFINE(IA64_ITC_LASTCYCLE_OFFSET,
+                offsetof (struct itc_jitter_data_t, itc_lastcycle));
 }
diff --git a/arch/ia64/kernel/cyclone.c b/arch/ia64/kernel/cyclone.c
index e00b21514f7c..2fd96d9062a1 100644
--- a/arch/ia64/kernel/cyclone.c
+++ b/arch/ia64/kernel/cyclone.c
@@ -3,6 +3,7 @@
 #include <linux/time.h>
 #include <linux/errno.h>
 #include <linux/timex.h>
+#include <linux/clocksource.h>
 #include <asm/io.h>
 
 /* IBM Summit (EXA) Cyclone counter code*/
@@ -18,13 +19,21 @@ void __init cyclone_setup(void)
         use_cyclone = 1;
 }
 
+static void __iomem *cyclone_mc;
 
-struct time_interpolator cyclone_interpolator = {
-        .source =       TIME_SOURCE_MMIO64,
-        .shift =        16,
-        .frequency =    CYCLONE_TIMER_FREQ,
-        .drift =        -100,
-        .mask =         (1LL << 40) - 1
+static cycle_t read_cyclone(void)
+{
+        return (cycle_t)readq((void __iomem *)cyclone_mc);
+}
+
+static struct clocksource clocksource_cyclone = {
+        .name           = "cyclone",
+        .rating         = 300,
+        .read           = read_cyclone,
+        .mask           = (1LL << 40) - 1,
+        .mult           = 0, /*to be caluclated*/
+        .shift          = 16,
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
 int __init init_cyclone_clock(void)
@@ -44,13 +53,15 @@ int __init init_cyclone_clock(void)
         offset = (CYCLONE_CBAR_ADDR);
         reg = (u64*)ioremap_nocache(offset, sizeof(u64));
         if(!reg){
-                printk(KERN_ERR "Summit chipset: Could not find valid CBAR register.\n");
+                printk(KERN_ERR "Summit chipset: Could not find valid CBAR"
+                                " register.\n");
                 use_cyclone = 0;
                 return -ENODEV;
         }
         base = readq(reg);
         if(!base){
-                printk(KERN_ERR "Summit chipset: Could not find valid CBAR value.\n");
+                printk(KERN_ERR "Summit chipset: Could not find valid CBAR"
+                                " value.\n");
                 use_cyclone = 0;
                 return -ENODEV;
         }
@@ -60,7 +71,8 @@ int __init init_cyclone_clock(void)
         offset = (base + CYCLONE_PMCC_OFFSET);
         reg = (u64*)ioremap_nocache(offset, sizeof(u64));
         if(!reg){
-                printk(KERN_ERR "Summit chipset: Could not find valid PMCC register.\n");
+                printk(KERN_ERR "Summit chipset: Could not find valid PMCC"
+                                " register.\n");
                 use_cyclone = 0;
                 return -ENODEV;
         }
@@ -71,7 +83,8 @@ int __init init_cyclone_clock(void)
         offset = (base + CYCLONE_MPCS_OFFSET);
         reg = (u64*)ioremap_nocache(offset, sizeof(u64));
         if(!reg){
-                printk(KERN_ERR "Summit chipset: Could not find valid MPCS register.\n");
+                printk(KERN_ERR "Summit chipset: Could not find valid MPCS"
+                                " register.\n");
                 use_cyclone = 0;
                 return -ENODEV;
         }
@@ -82,7 +95,8 @@ int __init init_cyclone_clock(void)
         offset = (base + CYCLONE_MPMC_OFFSET);
         cyclone_timer = (u32*)ioremap_nocache(offset, sizeof(u32));
         if(!cyclone_timer){
-                printk(KERN_ERR "Summit chipset: Could not find valid MPMC register.\n");
+                printk(KERN_ERR "Summit chipset: Could not find valid MPMC"
+                                " register.\n");
                 use_cyclone = 0;
                 return -ENODEV;
         }
@@ -93,7 +107,8 @@ int __init init_cyclone_clock(void)
                 int stall = 100;
                 while(stall--) barrier();
                 if(readl(cyclone_timer) == old){
-                        printk(KERN_ERR "Summit chipset: Counter not counting! DISABLED\n");
+                        printk(KERN_ERR "Summit chipset: Counter not counting!"
+                                        " DISABLED\n");
                         iounmap(cyclone_timer);
                         cyclone_timer = 0;
                         use_cyclone = 0;
@@ -101,8 +116,11 @@ int __init init_cyclone_clock(void)
                 }
         }
         /* initialize last tick */
-        cyclone_interpolator.addr = cyclone_timer;
-        register_time_interpolator(&cyclone_interpolator);
+        cyclone_mc = cyclone_timer;
+        clocksource_cyclone.fsys_mmio = cyclone_timer;
+        clocksource_cyclone.mult = clocksource_hz2mult(CYCLONE_TIMER_FREQ,
+                                                clocksource_cyclone.shift);
+        clocksource_register(&clocksource_cyclone);
 
         return 0;
 }
diff --git a/arch/ia64/kernel/fsys.S b/arch/ia64/kernel/fsys.S
index 3f926c2dc708..44841971f077 100644
--- a/arch/ia64/kernel/fsys.S
+++ b/arch/ia64/kernel/fsys.S
@@ -147,12 +147,11 @@ ENTRY(fsys_set_tid_address)
         FSYS_RETURN
 END(fsys_set_tid_address)
 
-/*
- * Ensure that the time interpolator structure is compatible with the asm code
- */
-#if IA64_TIME_INTERPOLATOR_SOURCE_OFFSET !=0 || IA64_TIME_INTERPOLATOR_SHIFT_OFFSET != 2 \
-        || IA64_TIME_INTERPOLATOR_JITTER_OFFSET != 3 || IA64_TIME_INTERPOLATOR_NSEC_OFFSET != 4
-#error fsys_gettimeofday incompatible with changes to struct time_interpolator
+#if IA64_GTOD_LOCK_OFFSET !=0
+#error fsys_gettimeofday incompatible with changes to struct fsyscall_gtod_data_t
+#endif
+#if IA64_ITC_JITTER_OFFSET !=0
+#error fsys_gettimeofday incompatible with changes to struct itc_jitter_data_t
 #endif
 #define CLOCK_REALTIME 0
 #define CLOCK_MONOTONIC 1
@@ -179,126 +178,124 @@ ENTRY(fsys_gettimeofday)
         // r11 = preserved: saved ar.pfs
         // r12 = preserved: memory stack
         // r13 = preserved: thread pointer
-        // r14 = address of mask / mask
+        // r14 = address of mask / mask value
         // r15 = preserved: system call number
         // r16 = preserved: current task pointer
-        // r17 = wall to monotonic use
-        // r18 = time_interpolator->offset
-        // r19 = address of wall_to_monotonic
-        // r20 = pointer to struct time_interpolator / pointer to time_interpolator->address
-        // r21 = shift factor
-        // r22 = address of time interpolator->last_counter
-        // r23 = address of time_interpolator->last_cycle
-        // r24 = adress of time_interpolator->offset
-        // r25 = last_cycle value
-        // r26 = last_counter value
-        // r27 = pointer to xtime
+        // r17 = (not used)
+        // r18 = (not used)
+        // r19 = address of itc_lastcycle
+        // r20 = struct fsyscall_gtod_data (= address of gtod_lock.sequence)
+        // r21 = address of mmio_ptr
+        // r22 = address of wall_time or monotonic_time
+        // r23 = address of shift / value
+        // r24 = address mult factor / cycle_last value
+        // r25 = itc_lastcycle value
+        // r26 = address clocksource cycle_last
+        // r27 = (not used)
         // r28 = sequence number at the beginning of critcal section
-        // r29 = address of seqlock
+        // r29 = address of itc_jitter
         // r30 = time processing flags / memory address
         // r31 = pointer to result
         // Predicates
         // p6,p7 short term use
         // p8 = timesource ar.itc
         // p9 = timesource mmio64
-        // p10 = timesource mmio32
+        // p10 = timesource mmio32 - not used
         // p11 = timesource not to be handled by asm code
-        // p12 = memory time source ( = p9 | p10)
-        // p13 = do cmpxchg with time_interpolator_last_cycle
+        // p12 = memory time source ( = p9 | p10) - not used
+        // p13 = do cmpxchg with itc_lastcycle
         // p14 = Divide by 1000
         // p15 = Add monotonic
         //
-        // Note that instructions are optimized for McKinley. McKinley can process two
-        // bundles simultaneously and therefore we continuously try to feed the CPU
-        // two bundles and then a stop.
-        tnat.nz p6,p0 = r31     // branch deferred since it does not fit into bundle structure
+        // Note that instructions are optimized for McKinley. McKinley can
+        // process two bundles simultaneously and therefore we continuously
+        // try to feed the CPU two bundles and then a stop.
+        //
+        // Additional note that code has changed a lot. Optimization is TBD.
+        // Comments begin with "?" are maybe outdated.
+        tnat.nz p6,p0 = r31     // ? branch deferred to fit later bundle
         mov pr = r30,0xc000     // Set predicates according to function
         add r2 = TI_FLAGS+IA64_TASK_SIZE,r16
-        movl r20 = time_interpolator
+        movl r20 = fsyscall_gtod_data // load fsyscall gettimeofday data address
         ;;
-        ld8 r20 = [r20]         // get pointer to time_interpolator structure
-        movl r29 = xtime_lock
+        movl r29 = itc_jitter_data      // itc_jitter
+        add r22 = IA64_GTOD_WALL_TIME_OFFSET,r20        // wall_time
         ld4 r2 = [r2]           // process work pending flags
-        movl r27 = xtime
-        ;;      // only one bundle here
-        ld8 r21 = [r20]         // first quad with control information
+        ;;
+(p15)   add r22 = IA64_GTOD_MONO_TIME_OFFSET,r20        // monotonic_time
+        add r21 = IA64_CLKSRC_MMIO_OFFSET,r20
+        add r19 = IA64_ITC_LASTCYCLE_OFFSET,r29
         and r2 = TIF_ALLWORK_MASK,r2
-(p6)    br.cond.spnt.few .fail_einval   // deferred branch
+(p6)    br.cond.spnt.few .fail_einval   // ? deferred branch
         ;;
-        add r10 = IA64_TIME_INTERPOLATOR_ADDRESS_OFFSET,r20
-        extr r3 = r21,32,32     // time_interpolator->nsec_per_cyc
-        extr r8 = r21,0,16      // time_interpolator->source
+        add r26 = IA64_CLKSRC_CYCLE_LAST_OFFSET,r20 // clksrc_cycle_last
         cmp.ne p6, p0 = 0, r2   // Fallback if work is scheduled
 (p6)    br.cond.spnt.many fsys_fallback_syscall
         ;;
-        cmp.eq p8,p12 = 0,r8    // Check for cpu timer
-        cmp.eq p9,p0 = 1,r8     // MMIO64 ?
-        extr r2 = r21,24,8      // time_interpolator->jitter
-        cmp.eq p10,p0 = 2,r8    // MMIO32 ?
-        cmp.ltu p11,p0 = 2,r8   // function or other clock
-(p11)   br.cond.spnt.many fsys_fallback_syscall
+        // Begin critical section
+.time_redo:
+        ld4.acq r28 = [r20]     // gtod_lock.sequence, Must take first
+        ;;
+        and r28 = ~1,r28        // And make sequence even to force retry if odd
         ;;
-        setf.sig f7 = r3        // Setup for scaling of counter
-(p15)   movl r19 = wall_to_monotonic
-(p12)   ld8 r30 = [r10]
-        cmp.ne p13,p0 = r2,r0   // need jitter compensation?
-        extr r21 = r21,16,8     // shift factor
+        ld8 r30 = [r21]         // clocksource->mmio_ptr
+        add r24 = IA64_CLKSRC_MULT_OFFSET,r20
+        ld4 r2 = [r29]          // itc_jitter value
+        add r23 = IA64_CLKSRC_SHIFT_OFFSET,r20
+        add r14 = IA64_CLKSRC_MASK_OFFSET,r20
         ;;
-.time_redo:
-        .pred.rel.mutex p8,p9,p10
-        ld4.acq r28 = [r29]     // xtime_lock.sequence. Must come first for locking purposes
+        ld4 r3 = [r24]          // clocksource mult value
+        ld8 r14 = [r14]         // clocksource mask value
+        cmp.eq p8,p9 = 0,r30    // use cpu timer if no mmio_ptr
         ;;
-        and r28 = ~1,r28        // Make sequence even to force retry if odd
+        setf.sig f7 = r3        // Setup for mult scaling of counter
+(p8)    cmp.ne p13,p0 = r2,r0   // need itc_jitter compensation, set p13
+        ld4 r23 = [r23]         // clocksource shift value
+        ld8 r24 = [r26]         // get clksrc_cycle_last value
+(p9)    cmp.eq p13,p0 = 0,r30   // if mmio_ptr, clear p13 jitter control
         ;;
+        .pred.rel.mutex p8,p9
 (p8)    mov r2 = ar.itc         // CPU_TIMER. 36 clocks latency!!!
-        add r22 = IA64_TIME_INTERPOLATOR_LAST_COUNTER_OFFSET,r20
-(p9)    ld8 r2 = [r30]          // readq(ti->address). Could also have latency issues..
-(p10)   ld4 r2 = [r30]          // readw(ti->address)
-(p13)   add r23 = IA64_TIME_INTERPOLATOR_LAST_CYCLE_OFFSET,r20
-        ;;                      // could be removed by moving the last add upward
-        ld8 r26 = [r22]         // time_interpolator->last_counter
-(p13)   ld8 r25 = [r23]         // time interpolator->last_cycle
-        add r24 = IA64_TIME_INTERPOLATOR_OFFSET_OFFSET,r20
-(p15)   ld8 r17 = [r19],IA64_TIMESPEC_TV_NSEC_OFFSET
-        ld8 r9 = [r27],IA64_TIMESPEC_TV_NSEC_OFFSET
-        add r14 = IA64_TIME_INTERPOLATOR_MASK_OFFSET, r20
-        ;;
-        ld8 r18 = [r24]         // time_interpolator->offset
-        ld8 r8 = [r27],-IA64_TIMESPEC_TV_NSEC_OFFSET    // xtime.tv_nsec
-(p13)   sub r3 = r25,r2 // Diff needed before comparison (thanks davidm)
-        ;;
-        ld8 r14 = [r14]         // time_interpolator->mask
-(p13)   cmp.gt.unc p6,p7 = r3,r0        // check if it is less than last. p6,p7 cleared
-        sub r10 = r2,r26        // current_counter - last_counter
-        ;;
-(p6)    sub r10 = r25,r26       // time we got was less than last_cycle
+(p9)    ld8 r2 = [r30]          // MMIO_TIMER. Could also have latency issues..
+(p13)   ld8 r25 = [r19]         // get itc_lastcycle value
+        ;;              // ? could be removed by moving the last add upward
+        ld8 r9 = [r22],IA64_TIMESPEC_TV_NSEC_OFFSET     // tv_sec
+        ;;
+        ld8 r8 = [r22],-IA64_TIMESPEC_TV_NSEC_OFFSET    // tv_nsec
+(p13)   sub r3 = r25,r2         // Diff needed before comparison (thanks davidm)
+        ;;
+(p13)   cmp.gt.unc p6,p7 = r3,r0 // check if it is less than last. p6,p7 cleared
+        sub r10 = r2,r24        // current_cycle - last_cycle
+        ;;
+(p6)    sub r10 = r25,r24       // time we got was less than last_cycle
 (p7)    mov ar.ccv = r25        // more than last_cycle. Prep for cmpxchg
         ;;
+(p7)    cmpxchg8.rel r3 = [r19],r2,ar.ccv
+        ;;
+(p7)    cmp.ne p7,p0 = r25,r3   // if cmpxchg not successful
+        ;;
+(p7)    sub r10 = r3,r24        // then use new last_cycle instead
+        ;;
         and r10 = r10,r14       // Apply mask
         ;;
         setf.sig f8 = r10
         nop.i 123
         ;;
-(p7)    cmpxchg8.rel r3 = [r23],r2,ar.ccv
-EX(.fail_efault, probe.w.fault r31, 3)  // This takes 5 cycles and we have spare time
+        // fault check takes 5 cycles and we have spare time
+EX(.fail_efault, probe.w.fault r31, 3)
         xmpy.l f8 = f8,f7       // nsec_per_cyc*(counter-last_counter)
-(p15)   add r9 = r9,r17         // Add wall to monotonic.secs to result secs
         ;;
-(p15)   ld8 r17 = [r19],-IA64_TIMESPEC_TV_NSEC_OFFSET
-(p7)    cmp.ne p7,p0 = r25,r3   // if cmpxchg not successful redo
-        // simulate tbit.nz.or p7,p0 = r28,0
+        // ? simulate tbit.nz.or p7,p0 = r28,0
         getf.sig r2 = f8
         mf
-        add r8 = r8,r18         // Add time interpolator offset
         ;;
-        ld4 r10 = [r29]         // xtime_lock.sequence
-(p15)   add r8 = r8, r17        // Add monotonic.nsecs to nsecs
-        shr.u r2 = r2,r21
-        ;;              // overloaded 3 bundles!
-        // End critical section.
+        ld4 r10 = [r20]         // gtod_lock.sequence
+        shr.u r2 = r2,r23       // shift by factor
+        ;;              // ? overloaded 3 bundles!
         add r8 = r8,r2          // Add xtime.nsecs
-        cmp4.ne.or p7,p0 = r28,r10
-(p7)    br.cond.dpnt.few .time_redo     // sequence number changed ?
+        cmp4.ne p7,p0 = r28,r10
+(p7)    br.cond.dpnt.few .time_redo     // sequence number changed, redo
+        // End critical section.
         // Now r8=tv->tv_nsec and r9=tv->tv_sec
         mov r10 = r0
         movl r2 = 1000000000
@@ -308,19 +305,19 @@ EX(.fail_efault, probe.w.fault r31, 3)	// This takes 5 cycles and we have spare
 .time_normalize:
         mov r21 = r8
         cmp.ge p6,p0 = r8,r2
-(p14)   shr.u r20 = r8, 3               // We can repeat this if necessary just wasting some time
+(p14)   shr.u r20 = r8, 3 // We can repeat this if necessary just wasting time
         ;;
 (p14)   setf.sig f8 = r20
 (p6)    sub r8 = r8,r2
-(p6)    add r9 = 1,r9                   // two nops before the branch.
-(p14)   setf.sig f7 = r3                // Chances for repeats are 1 in 10000 for gettod
+(p6)    add r9 = 1,r9           // two nops before the branch.
+(p14)   setf.sig f7 = r3        // Chances for repeats are 1 in 10000 for gettod
 (p6)    br.cond.dpnt.few .time_normalize
         ;;
         // Divided by 8 though shift. Now divide by 125
         // The compiler was able to do that with a multiply
         // and a shift and we do the same
-EX(.fail_efault, probe.w.fault r23, 3)          // This also costs 5 cycles
-(p14)   xmpy.hu f8 = f8, f7                     // xmpy has 5 cycles latency so use it...
+EX(.fail_efault, probe.w.fault r23, 3)  // This also costs 5 cycles
+(p14)   xmpy.hu f8 = f8, f7             // xmpy has 5 cycles latency so use it
         ;;
         mov r8 = r0
 (p14)   getf.sig r2 = f8
diff --git a/arch/ia64/kernel/fsyscall_gtod_data.h b/arch/ia64/kernel/fsyscall_gtod_data.h
new file mode 100644
index 000000000000..490dab55fba3
--- /dev/null
+++ b/arch/ia64/kernel/fsyscall_gtod_data.h
@@ -0,0 +1,23 @@
+/*
+ * (c) Copyright 2007 Hewlett-Packard Development Company, L.P.
+ *        Contributed by Peter Keilty <peter.keilty@hp.com>
+ *
+ * fsyscall gettimeofday data
+ */
+
+struct fsyscall_gtod_data_t {
+        seqlock_t       lock;
+        struct timespec wall_time;
+        struct timespec monotonic_time;
+        cycle_t         clk_mask;
+        u32             clk_mult;
+        u32             clk_shift;
+        void            *clk_fsys_mmio;
+        cycle_t         clk_cycle_last;
+} __attribute__ ((aligned (L1_CACHE_BYTES)));
+
+struct itc_jitter_data_t {
+        int             itc_jitter;
+        cycle_t         itc_lastcycle;
+} __attribute__ ((aligned (L1_CACHE_BYTES)));
+
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 3486fe7d6e65..627785c48ea9 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -19,6 +19,7 @@
 #include <linux/interrupt.h>
 #include <linux/efi.h>
 #include <linux/timex.h>
+#include <linux/clocksource.h>
 
 #include <asm/machvec.h>
 #include <asm/delay.h>
@@ -28,6 +29,16 @@
 #include <asm/sections.h>
 #include <asm/system.h>
 
+#include "fsyscall_gtod_data.h"
+
+static cycle_t itc_get_cycles(void);
+
+struct fsyscall_gtod_data_t fsyscall_gtod_data = {
+        .lock = SEQLOCK_UNLOCKED,
+};
+
+struct itc_jitter_data_t itc_jitter_data;
+
 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
 
 #ifdef CONFIG_IA64_DEBUG_IRQ
@@ -37,11 +48,16 @@ EXPORT_SYMBOL(last_cli_ip);
 
 #endif
 
-static struct time_interpolator itc_interpolator = {
-        .shift = 16,
-        .mask = 0xffffffffffffffffLL,
-        .source = TIME_SOURCE_CPU
+static struct clocksource clocksource_itc = {
+        .name           = "itc",
+        .rating         = 350,
+        .read           = itc_get_cycles,
+        .mask           = 0xffffffffffffffff,
+        .mult           = 0, /*to be caluclated*/
+        .shift          = 16,
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
+static struct clocksource *itc_clocksource;
 
 static irqreturn_t
 timer_interrupt (int irq, void *dev_id)
@@ -210,8 +226,6 @@ ia64_init_itm (void)
                                         + itc_freq/2)/itc_freq;
 
         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
-                itc_interpolator.frequency = local_cpu_data->itc_freq;
-                itc_interpolator.drift = itc_drift;
 #ifdef CONFIG_SMP
                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
                  * Jitter compensation requires a cmpxchg which may limit
@@ -223,15 +237,50 @@ ia64_init_itm (void)
                  * even going backward) if the ITC offsets between the individual CPUs
                  * are too large.
                  */
-                if (!nojitter) itc_interpolator.jitter = 1;
+                if (!nojitter)
+                        itc_jitter_data.itc_jitter = 1;
 #endif
-                register_time_interpolator(&itc_interpolator);
         }
 
         /* Setup the CPU local timer tick */
         ia64_cpu_local_tick();
+
+        if (!itc_clocksource) {
+                /* Sort out mult/shift values: */
+                clocksource_itc.mult =
+                        clocksource_hz2mult(local_cpu_data->itc_freq,
+                                                clocksource_itc.shift);
+                clocksource_register(&clocksource_itc);
+                itc_clocksource = &clocksource_itc;
+        }
 }
 
+static cycle_t itc_get_cycles()
+{
+        u64 lcycle, now, ret;
+
+        if (!itc_jitter_data.itc_jitter)
+                return get_cycles();
+
+        lcycle = itc_jitter_data.itc_lastcycle;
+        now = get_cycles();
+        if (lcycle && time_after(lcycle, now))
+                return lcycle;
+
+        /*
+         * Keep track of the last timer value returned.
+         * In an SMP environment, you could lose out in contention of
+         * cmpxchg. If so, your cmpxchg returns new value which the
+         * winner of contention updated to. Use the new value instead.
+         */
+        ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
+        if (unlikely(ret != lcycle))
+                return ret;
+
+        return now;
+}
+
+
 static struct irqaction timer_irqaction = {
         .handler =      timer_interrupt,
         .flags =        IRQF_DISABLED | IRQF_IRQPOLL,
@@ -307,3 +356,34 @@ ia64_setup_printk_clock(void)
         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
                 ia64_printk_clock = ia64_itc_printk_clock;
 }
+
+void update_vsyscall(struct timespec *wall, struct clocksource *c)
+{
+        unsigned long flags;
+
+        write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
+
+        /* copy fsyscall clock data */
+        fsyscall_gtod_data.clk_mask = c->mask;
+        fsyscall_gtod_data.clk_mult = c->mult;
+        fsyscall_gtod_data.clk_shift = c->shift;
+        fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
+        fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
+
+        /* copy kernel time structures */
+        fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
+        fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
+        fsyscall_gtod_data.monotonic_time.tv_sec = wall_to_monotonic.tv_sec
+                                                        + wall->tv_sec;
+        fsyscall_gtod_data.monotonic_time.tv_nsec = wall_to_monotonic.tv_nsec
+                                                        + wall->tv_nsec;
+
+        /* normalize */
+        while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
+                fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
+                fsyscall_gtod_data.monotonic_time.tv_sec++;
+        }
+
+        write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
+}
+
diff --git a/arch/ia64/sn/kernel/sn2/timer.c b/arch/ia64/sn/kernel/sn2/timer.c
index 56a88b6df4b4..19e25d2b64fc 100644
--- a/arch/ia64/sn/kernel/sn2/timer.c
+++ b/arch/ia64/sn/kernel/sn2/timer.c
@@ -11,6 +11,7 @@
 #include <linux/sched.h>
 #include <linux/time.h>
 #include <linux/interrupt.h>
+#include <linux/clocksource.h>
 
 #include <asm/hw_irq.h>
 #include <asm/system.h>
@@ -22,11 +23,21 @@
 
 extern unsigned long sn_rtc_cycles_per_second;
 
-static struct time_interpolator sn2_interpolator = {
-        .drift = -1,
-        .shift = 10,
-        .mask = (1LL << 55) - 1,
-        .source = TIME_SOURCE_MMIO64
+static void __iomem *sn2_mc;
+
+static cycle_t read_sn2(void)
+{
+        return (cycle_t)readq(sn2_mc);
+}
+
+static struct clocksource clocksource_sn2 = {
+        .name           = "sn2_rtc",
+        .rating         = 300,
+        .read           = read_sn2,
+        .mask           = (1LL << 55) - 1,
+        .mult           = 0,
+        .shift          = 10,
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
 /*
@@ -47,9 +58,11 @@ ia64_sn_udelay (unsigned long usecs)
 
 void __init sn_timer_init(void)
 {
-        sn2_interpolator.frequency = sn_rtc_cycles_per_second;
-        sn2_interpolator.addr = RTC_COUNTER_ADDR;
-        register_time_interpolator(&sn2_interpolator);
+        sn2_mc = RTC_COUNTER_ADDR;
+        clocksource_sn2.fsys_mmio = RTC_COUNTER_ADDR;
+        clocksource_sn2.mult = clocksource_hz2mult(sn_rtc_cycles_per_second,
+                                                        clocksource_sn2.shift);
+        clocksource_register(&clocksource_sn2);
 
         ia64_udelay = &ia64_sn_udelay;
 }