[PATCH] ppc32: fix last_jiffy time comparison

This fixes a hang on ppc32.

The problem was that I was comparing a 32-bit quantity with a 64-bit
quantity, and consequently time wasn't advancing.  This makes us use a
64-bit quantity on all platforms, which ends up simplifying the code
since we can now get rid of the tb_last_stamp variable (which actually
fixes another bug that Ben H and I noticed while going carefully through
the code).

This works fine on my G4 tibook.  Let me know how it goes on your
machines.

Acked-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 17 deletions

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 18e59e43d2b3..a124499e65d9 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -125,15 +125,8 @@ static long timezone_offset;
 unsigned long ppc_proc_freq;
 unsigned long ppc_tb_freq;
 
-u64 tb_last_jiffy __cacheline_aligned_in_smp;
-unsigned long tb_last_stamp;
-
-/*
- * Note that on ppc32 this only stores the bottom 32 bits of
- * the timebase value, but that's enough to tell when a jiffy
- * has passed.
- */
-DEFINE_PER_CPU(unsigned long, last_jiffy);
+static u64 tb_last_jiffy __cacheline_aligned_in_smp;
+static DEFINE_PER_CPU(u64, last_jiffy);
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
 /*
@@ -458,7 +451,7 @@ void do_gettimeofday(struct timeval *tv)
                 do {
                         seq = read_seqbegin_irqsave(&xtime_lock, flags);
                         sec = xtime.tv_sec;
-                        nsec = xtime.tv_nsec + tb_ticks_since(tb_last_stamp);
+                        nsec = xtime.tv_nsec + tb_ticks_since(tb_last_jiffy);
                 } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
                 usec = nsec / 1000;
                 while (usec >= 1000000) {
@@ -700,7 +693,6 @@ void timer_interrupt(struct pt_regs * regs)
                 tb_next_jiffy = tb_last_jiffy + tb_ticks_per_jiffy;
                 if (per_cpu(last_jiffy, cpu) >= tb_next_jiffy) {
                         tb_last_jiffy = tb_next_jiffy;
-                        tb_last_stamp = per_cpu(last_jiffy, cpu);
                         do_timer(regs);
                         timer_recalc_offset(tb_last_jiffy);
                         timer_check_rtc();
@@ -749,7 +741,7 @@ void __init smp_space_timers(unsigned int max_cpus)
         int i;
         unsigned long half = tb_ticks_per_jiffy / 2;
         unsigned long offset = tb_ticks_per_jiffy / max_cpus;
-        unsigned long previous_tb = per_cpu(last_jiffy, boot_cpuid);
+        u64 previous_tb = per_cpu(last_jiffy, boot_cpuid);
 
         /* make sure tb > per_cpu(last_jiffy, cpu) for all cpus always */
         previous_tb -= tb_ticks_per_jiffy;
@@ -830,7 +822,7 @@ int do_settimeofday(struct timespec *tv)
          * and therefore the (jiffies - wall_jiffies) computation
          * has been removed.
          */
-        tb_delta = tb_ticks_since(tb_last_stamp);
+        tb_delta = tb_ticks_since(tb_last_jiffy);
         tb_delta = mulhdu(tb_delta, do_gtod.varp->tb_to_xs); /* in xsec */
         new_nsec -= SCALE_XSEC(tb_delta, 1000000000);
 
@@ -950,8 +942,7 @@ void __init time_init(void)
         if (__USE_RTC()) {
                 /* 601 processor: dec counts down by 128 every 128ns */
                 ppc_tb_freq = 1000000000;
-                tb_last_stamp = get_rtcl();
-                tb_last_jiffy = tb_last_stamp;
+                tb_last_jiffy = get_rtcl();
         } else {
                 /* Normal PowerPC with timebase register */
                 ppc_md.calibrate_decr();
@@ -959,7 +950,7 @@ void __init time_init(void)
                        ppc_tb_freq / 1000000, ppc_tb_freq % 1000000);
                 printk(KERN_DEBUG "time_init: processor frequency   = %lu.%.6lu MHz\n",
                        ppc_proc_freq / 1000000, ppc_proc_freq % 1000000);
-                tb_last_stamp = tb_last_jiffy = get_tb();
+                tb_last_jiffy = get_tb();
         }
 
         tb_ticks_per_jiffy = ppc_tb_freq / HZ;
@@ -1036,7 +1027,7 @@ void __init time_init(void)
         do_gtod.varp = &do_gtod.vars[0];
         do_gtod.var_idx = 0;
         do_gtod.varp->tb_orig_stamp = tb_last_jiffy;
-        __get_cpu_var(last_jiffy) = tb_last_stamp;
+        __get_cpu_var(last_jiffy) = tb_last_jiffy;
         do_gtod.varp->stamp_xsec = (u64) xtime.tv_sec * XSEC_PER_SEC;
         do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
         do_gtod.varp->tb_to_xs = tb_to_xs;