提交 59937bcd 编写于 作者: M Matt Mackall 提交者: Linus Torvalds

[PATCH] RTC: Remove RTC UIP synchronization on PPC CHRP (arch/ppc)

Signed-off-by: NMatt Mackall <mpm@selenic.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
上级 3dedf53b
......@@ -119,33 +119,15 @@ int chrp_set_rtc_time(unsigned long nowtime)
unsigned long chrp_get_rtc_time(void)
{
unsigned int year, mon, day, hour, min, sec;
int uip, i;
/* The Linux interpretation of the CMOS clock register contents:
* When the Update-In-Progress (UIP) flag goes from 1 to 0, the
* RTC registers show the second which has precisely just started.
* Let's hope other operating systems interpret the RTC the same way.
*/
/* Since the UIP flag is set for about 2.2 ms and the clock
* is typically written with a precision of 1 jiffy, trying
* to obtain a precision better than a few milliseconds is
* an illusion. Only consistency is interesting, this also
* allows to use the routine for /dev/rtc without a potential
* 1 second kernel busy loop triggered by any reader of /dev/rtc.
*/
for ( i = 0; i<1000000; i++) {
uip = chrp_cmos_clock_read(RTC_FREQ_SELECT);
do {
sec = chrp_cmos_clock_read(RTC_SECONDS);
min = chrp_cmos_clock_read(RTC_MINUTES);
hour = chrp_cmos_clock_read(RTC_HOURS);
day = chrp_cmos_clock_read(RTC_DAY_OF_MONTH);
mon = chrp_cmos_clock_read(RTC_MONTH);
year = chrp_cmos_clock_read(RTC_YEAR);
uip |= chrp_cmos_clock_read(RTC_FREQ_SELECT);
if ((uip & RTC_UIP)==0) break;
}
} while (sec != chrp_cmos_clock_read(RTC_SECONDS));
if (!(chrp_cmos_clock_read(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
{
......
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