From 79250ef3e263ef23c16c3c06a50834f0dcca4426 Mon Sep 17 00:00:00 2001 From: Dario Binacchi Date: Wed, 2 Jun 2021 22:38:01 +0200 Subject: [PATCH] rtc: davinci: check BUSY bit before set TC registers MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Lokesh Vutla Link: https://lore.kernel.org/r/20210602203805.11494-5-dariobin@libero.it --- 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 99ae31e..7b8c729 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; } -- 2.7.4