[POWERPC] Fix timekeeping on PowerPC 601

Recent changes to the timekeeping code broke support for the PowerPC 601
processor which doesn't have the usual timebase facility but a slightly
different thing called (yuck) the RTC.

This fixes it, boot tested on an old 601 based PowerMac 7200.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 10 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 727a6699f2f4..c627cf86d1e3 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -239,7 +239,7 @@ static void snapshot_tb_and_purr(void *data)
         struct cpu_purr_data *p = &__get_cpu_var(cpu_purr_data);
 
         local_irq_save(flags);
-        p->tb = mftb();
+        p->tb = get_tb_or_rtc();
         p->purr = mfspr(SPRN_PURR);
         wmb();
         p->initialized = 1;
@@ -317,7 +317,7 @@ static void snapshot_purr(void)
  */
 void snapshot_timebase(void)
 {
-        __get_cpu_var(last_jiffy) = get_tb();
+        __get_cpu_var(last_jiffy) = get_tb_or_rtc();
         snapshot_purr();
 }
 
@@ -684,6 +684,8 @@ void timer_interrupt(struct pt_regs * regs)
 
                 write_seqlock(&xtime_lock);
                 tb_next_jiffy = tb_last_jiffy + tb_ticks_per_jiffy;
+                if (__USE_RTC() && tb_next_jiffy >= 1000000000)
+                        tb_next_jiffy -= 1000000000;
                 if (per_cpu(last_jiffy, cpu) >= tb_next_jiffy) {
                         tb_last_jiffy = tb_next_jiffy;
                         do_timer(1);
@@ -977,7 +979,7 @@ void __init time_init(void)
         tb_to_ns_scale = scale;
         tb_to_ns_shift = shift;
         /* Save the current timebase to pretty up CONFIG_PRINTK_TIME */
-        boot_tb = get_tb();
+        boot_tb = get_tb_or_rtc();
 
         tm = get_boot_time();
 
diff --git a/include/asm-powerpc/time.h b/include/asm-powerpc/time.h
index d7f5ddfbaac7..c104c15c6625 100644
--- a/include/asm-powerpc/time.h
+++ b/include/asm-powerpc/time.h
@@ -149,6 +149,11 @@ static inline u64 get_tb(void)
 }
 #endif /* !CONFIG_PPC64 */
 
+static inline u64 get_tb_or_rtc(void)
+{
+        return __USE_RTC() ? get_rtc() : get_tb();
+}
+
 static inline void set_tb(unsigned int upper, unsigned int lower)
 {
         mtspr(SPRN_TBWL, 0);