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rtc: davinci: check BUSY bit before set TC registers

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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>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210602203805.11494-5-dariobin@libero.it
This commit is contained in:
Dario Binacchi
2021-06-02 22:38:01 +02:00
committed by Lokesh Vutla
parent 82a456a085
commit 79250ef3e2
1 changed files with 36 additions and 9 deletions
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45
drivers/rtc/davinci.c
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@@ -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;
}