rtc: zynqmp: Update seconds time programming logic

We program RTC time using SET_TIME_WRITE register and read the RTC
current time using CURRENT_TIME register. When we set the time by
writing into SET_TIME_WRITE Register and immediately try to read the
rtc time from CURRENT_TIME register, the previous old value is
returned instead of the new loaded time. This is because RTC takes
nearly 1 sec to update the  new loaded value into the CURRENT_TIME
register. This behaviour is expected in our RTC IP.

This patch updates the driver to read the current time from SET_TIME_WRITE
register instead of CURRENT_TIME when rtc time is requested within an 1sec
period after setting the RTC time. Doing so will ensure the correct time is
given to the user.

Since there is a delay of 1sec in updating the CURRENT_TIME we are loading
set time +1sec while programming the SET_TIME_WRITE register, doing this
will give correct time without any delay when read from CURRENT_TIME.

Signed-off-by: Anurag Kumar Vulisha <anuragku@xilinx.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
index f87f971..da18a8a 100644 (file)
--- a/drivers/rtc/rtc-zynqmp.c
+++ b/drivers/rtc/rtc-zynqmp.c
@@ -64,7 +64,12 @@ static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)
        struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
        unsigned long new_time;
 
-       new_time = rtc_tm_to_time64(tm);
+       /*
+        * The value written will be updated after 1 sec into the
+        * seconds read register, so we need to program time +1 sec
+        * to get the correct time on read.
+        */
+       new_time = rtc_tm_to_time64(tm) + 1;
 
        if (new_time > RTC_SEC_MAX_VAL)
                return -EINVAL;
@@ -78,14 +83,44 @@ static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)
 
        writel(new_time, xrtcdev->reg_base + RTC_SET_TM_WR);
 
+       /*
+        * Clear the rtc interrupt status register after setting the
+        * time. During a read_time function, the code should read the
+        * RTC_INT_STATUS register and if bit 0 is still 0, it means
+        * that one second has not elapsed yet since RTC was set and
+        * the current time should be read from SET_TIME_READ register;
+        * otherwise, CURRENT_TIME register is read to report the time
+        */
+       writel(RTC_INT_SEC, xrtcdev->reg_base + RTC_INT_STS);
+
        return 0;
 }
 
 static int xlnx_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
+       u32 status;
+       unsigned long read_time;
        struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
 
-       rtc_time64_to_tm(readl(xrtcdev->reg_base + RTC_CUR_TM), tm);
+       status = readl(xrtcdev->reg_base + RTC_INT_STS);
+
+       if (status & RTC_INT_SEC) {
+               /*
+                * RTC has updated the CURRENT_TIME with the time written into
+                * SET_TIME_WRITE register.
+                */
+               rtc_time64_to_tm(readl(xrtcdev->reg_base + RTC_CUR_TM), tm);
+       } else {
+               /*
+                * Time written in SET_TIME_WRITE has not yet updated into
+                * the seconds read register, so read the time from the
+                * SET_TIME_WRITE instead of CURRENT_TIME register.
+                * Since we add +1 sec while writing, we need to -1 sec while
+                * reading.
+                */
+               read_time = readl(xrtcdev->reg_base + RTC_SET_TM_RD) - 1;
+               rtc_time64_to_tm(read_time, tm);
+       }
 
        return rtc_valid_tm(tm);
 }
@@ -166,11 +201,9 @@ static irqreturn_t xlnx_rtc_interrupt(int irq, void *id)
        if (!(status & (RTC_INT_SEC | RTC_INT_ALRM)))
                return IRQ_NONE;
 
-       /* Clear interrupt */
-       writel(status, xrtcdev->reg_base + RTC_INT_STS);
+       /* Clear RTC_INT_ALRM interrupt only */
+       writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_STS);
 
-       if (status & RTC_INT_SEC)
-               rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_UF);
        if (status & RTC_INT_ALRM)
                rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_AF);