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Subject[PATCH] PPC64 Set time-related systemcfg fields
Somewhere along the line we lost the code that updates some fields of
the systemcfg structure that are used for translating timebase values
to time of day. I want to get rid of the systemcfg structure
eventually, but applications are using it (and in particular these
fields) and I don't want to break the ABI in a stable kernel series.

Please apply.

Signed-off-by: Paul Mackerras <paulus@samba.org>

diff -urN linux-2.5/arch/ppc64/kernel/smp.c ppc64/arch/ppc64/kernel/smp.c
--- linux-2.5/arch/ppc64/kernel/smp.c 2004-08-06 07:15:01.000000000 +1000
+++ ppc64/arch/ppc64/kernel/smp.c 2004-08-11 08:11:22.080930712 +1000
@@ -843,6 +843,7 @@
* number of msecs off until someone does a settimeofday()
*/
do_gtod.tb_orig_stamp = tb_last_stamp;
+ systemcfg->tb_orig_stamp = tb_last_stamp;

look_for_more_cpus();
#endif
diff -urN linux-2.5/arch/ppc64/kernel/time.c ppc64/arch/ppc64/kernel/time.c
--- linux-2.5/arch/ppc64/kernel/time.c 2004-07-05 11:49:19.000000000 +1000
+++ ppc64/arch/ppc64/kernel/time.c 2004-08-11 08:08:53.345044408 +1000
@@ -101,6 +101,8 @@
extern unsigned long lpevent_count;
extern int smp_tb_synchronized;

+extern struct timezone sys_tz;
+
void ppc_adjtimex(void);

static unsigned adjusting_time = 0;
@@ -233,6 +235,8 @@
do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
tb_to_xs = divres.result_low;
do_gtod.varp->tb_to_xs = tb_to_xs;
+ systemcfg->tb_ticks_per_sec = tb_ticks_per_sec;
+ systemcfg->tb_to_xs = tb_to_xs;
}
else {
printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
@@ -408,6 +412,7 @@
new_xsec += new_sec * XSEC_PER_SEC;
if ( new_xsec > delta_xsec ) {
do_gtod.varp->stamp_xsec = new_xsec - delta_xsec;
+ systemcfg->stamp_xsec = new_xsec - delta_xsec;
}
else {
/* This is only for the case where the user is setting the time
@@ -416,8 +421,13 @@
* the time to Jan 5, 1970 */
do_gtod.varp->stamp_xsec = new_xsec;
do_gtod.tb_orig_stamp = tb_last_stamp;
+ systemcfg->stamp_xsec = new_xsec;
+ systemcfg->tb_orig_stamp = tb_last_stamp;
}

+ systemcfg->tz_minuteswest = sys_tz.tz_minuteswest;
+ systemcfg->tz_dsttime = sys_tz.tz_dsttime;
+
write_sequnlock_irqrestore(&xtime_lock, flags);
clock_was_set();
return 0;
@@ -520,6 +530,11 @@
do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
do_gtod.varp->tb_to_xs = tb_to_xs;
do_gtod.tb_to_us = tb_to_us;
+ systemcfg->tb_orig_stamp = tb_last_stamp;
+ systemcfg->tb_update_count = 0;
+ systemcfg->tb_ticks_per_sec = tb_ticks_per_sec;
+ systemcfg->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
+ systemcfg->tb_to_xs = tb_to_xs;

xtime_sync_interval = tb_ticks_per_sec - (tb_ticks_per_sec/8);
next_xtime_sync_tb = tb_last_stamp + xtime_sync_interval;
@@ -655,6 +670,22 @@
do_gtod.varp = temp_varp;
do_gtod.var_idx = temp_idx;

+ /*
+ * tb_update_count is used to allow the problem state gettimeofday code
+ * to assure itself that it sees a consistent view of the tb_to_xs and
+ * stamp_xsec variables. It reads the tb_update_count, then reads
+ * tb_to_xs and stamp_xsec and then reads tb_update_count again. If
+ * the two values of tb_update_count match and are even then the
+ * tb_to_xs and stamp_xsec values are consistent. If not, then it
+ * loops back and reads them again until this criteria is met.
+ */
+ ++(systemcfg->tb_update_count);
+ wmb();
+ systemcfg->tb_to_xs = new_tb_to_xs;
+ systemcfg->stamp_xsec = new_stamp_xsec;
+ wmb();
+ ++(systemcfg->tb_update_count);
+
write_sequnlock_irqrestore( &xtime_lock, flags );

}
-
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