To write correct data to the TC registers, the STATUS register must be read until the BUSY bit is equal to zero. Once the BUSY flag is zero, there is a 15 μs access period in which the TC registers can be programmed. The rtc_wait_not_busy() has been inspired by the Kernel.
Signed-off-by: Dario Binacchi dariobin@libero.it ---
(no changes since v1)
drivers/rtc/davinci.c | 45 ++++++++++++++++++++++++++++++++++--------- 1 file changed, 36 insertions(+), 9 deletions(-)
diff --git a/drivers/rtc/davinci.c b/drivers/rtc/davinci.c index 99ae31e2a5..7b8c729f3b 100644 --- a/drivers/rtc/davinci.c +++ b/drivers/rtc/davinci.c @@ -16,19 +16,39 @@ #define RTC_BASE DAVINCI_RTC_BASE #endif
-int rtc_get(struct rtc_time *tmp) +static int davinci_rtc_wait_not_busy(struct davinci_rtc *rtc) { - struct davinci_rtc *rtc = (struct davinci_rtc *)RTC_BASE; - unsigned long sec, min, hour, mday, wday, mon_cent, year; - unsigned long status; + int count; + u8 status;
status = readb(&rtc->status); if ((status & RTC_STATE_RUN) != RTC_STATE_RUN) { printf("RTC doesn't run\n"); return -1; } - if ((status & RTC_STATE_BUSY) == RTC_STATE_BUSY) - udelay(20); + + /* BUSY may stay active for 1/32768 second (~30 usec) */ + for (count = 0; count < 50; count++) { + if (!(status & RTC_STATE_BUSY)) + break; + + udelay(1); + status = readb(&rtc->status); + } + + /* now we have ~15 usec to read/write various registers */ + return 0; +} + +int rtc_get(struct rtc_time *tmp) +{ + struct davinci_rtc *rtc = (struct davinci_rtc *)RTC_BASE; + unsigned long sec, min, hour, mday, wday, mon_cent, year; + int ret; + + ret = davinci_rtc_wait_not_busy(rtc); + if (ret) + return ret;
sec = readb(&rtc->second); min = readb(&rtc->minutes); @@ -63,10 +83,12 @@ int rtc_get(struct rtc_time *tmp) int rtc_set(struct rtc_time *tmp) { struct davinci_rtc *rtc = (struct davinci_rtc *)RTC_BASE; + int ret; + + ret = davinci_rtc_wait_not_busy(rtc); + if (ret) + return ret;
- debug("Set DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n", - tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday, - tmp->tm_hour, tmp->tm_min, tmp->tm_sec); writeb(bin2bcd(tmp->tm_year % 100), &rtc->year); writeb(bin2bcd(tmp->tm_mon), &rtc->month);
@@ -75,6 +97,11 @@ int rtc_set(struct rtc_time *tmp) writeb(bin2bcd(tmp->tm_hour), &rtc->hours); writeb(bin2bcd(tmp->tm_min), &rtc->minutes); writeb(bin2bcd(tmp->tm_sec), &rtc->second); + + debug("Set DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n", + tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday, + tmp->tm_hour, tmp->tm_min, tmp->tm_sec); + return 0; }