powerpc: Fix some bugs in the new merged time code

I had the sense of the test for when to use the old 601-style RTC
registers inverted.  pmac_calibrate_decr and via_calibrate_decr
weren't setting ppc_tb_freq, on which all the further calculations
depended.  Lastly, update_gtod was losing the top 32 bits of
the new tb_to_xs value.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/time.c

@@ -222,7 +222,7 @@ static inline void timer_sync_xtime(unsigned long cur_tb)
  * between updates.
  */
 static inline void update_gtod(u64 new_tb_stamp, u64 new_stamp_xsec,
-			       unsigned int new_tb_to_xs)
+			       u64 new_tb_to_xs)
 {
 	unsigned temp_idx;
 	struct gettimeofday_vars *temp_varp;

arch/powerpc/platforms/powermac/time.c

@@ -216,8 +216,8 @@ via_calibrate_decr(void)
 		;
 	dend = get_dec();
 
+	ppc_tb_freq = (dstart - dend) * 100 / 6;
 	tb_ticks_per_jiffy = (dstart - dend) / ((6 * HZ)/100);
-	tb_to_us = mulhwu_scale_factor(dstart - dend, 60000);
 
 	printk(KERN_INFO "via_calibrate_decr: ticks per jiffy = %lu (%u ticks)\n",
 	       tb_ticks_per_jiffy, dstart - dend);
@@ -306,6 +306,5 @@ pmac_calibrate_decr(void)
 	freq = *fp;
 	printk("time_init: decrementer frequency = %u.%.6u MHz\n",
 	       freq/1000000, freq%1000000);
-	tb_ticks_per_jiffy = freq / HZ;
-	tb_to_us = mulhwu_scale_factor(freq, 1000000);
+	ppc_tb_freq = freq;
 }

include/asm-powerpc/time.h

@@ -75,7 +75,7 @@ struct div_result {
 /* Accessor functions for the timebase (RTC on 601) registers. */
 /* If one day CONFIG_POWER is added just define __USE_RTC as 1 */
 #ifdef CONFIG_6xx
-#define __USE_RTC()	cpu_has_feature(CPU_FTR_USE_TB)
+#define __USE_RTC()	(!cpu_has_feature(CPU_FTR_USE_TB))
 #else
 #define __USE_RTC()	0
 #endif