rtc: zynqmp: Write Calibration value before setting time

It is suggested to program CALIB_WRITE register with the calibration
value before updating the SET_TIME_WRITE register, doing so will
clear the Tick Counter and force the next second to be signaled
exactly in 1 second.

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 6adb603f29bc2b83a95c705856981c392a0da238..f87f971a72c20e0c6295105662bcc5a2dc8b2a33 100644 (file)
--- a/drivers/rtc/rtc-zynqmp.c
+++ b/drivers/rtc/rtc-zynqmp.c
@@ -56,6 +56,7 @@ struct xlnx_rtc_dev {
        void __iomem            *reg_base;
        int                     alarm_irq;
        int                     sec_irq;
+       int                     calibval;
 };
 
 static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)
@@ -68,6 +69,13 @@ static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)
        if (new_time > RTC_SEC_MAX_VAL)
                return -EINVAL;
 
+       /*
+        * Writing into calibration register will clear the Tick Counter and
+        * force the next second to be signaled exactly in 1 second period
+        */
+       xrtcdev->calibval &= RTC_CALIB_MASK;
+       writel(xrtcdev->calibval, (xrtcdev->reg_base + RTC_CALIB_WR));
+
        writel(new_time, xrtcdev->reg_base + RTC_SET_TM_WR);
 
        return 0;
@@ -121,7 +129,7 @@ static int xlnx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
        return 0;
 }
 
-static void xlnx_init_rtc(struct xlnx_rtc_dev *xrtcdev, u32 calibval)
+static void xlnx_init_rtc(struct xlnx_rtc_dev *xrtcdev)
 {
        u32 rtc_ctrl;
 
@@ -136,8 +144,8 @@ static void xlnx_init_rtc(struct xlnx_rtc_dev *xrtcdev, u32 calibval)
         * to default value suggested as per design spec
         * to correct RTC delay in frequency over period of time.
         */
-       calibval &= RTC_CALIB_MASK;
-       writel(calibval, (xrtcdev->reg_base + RTC_CALIB_WR));
+       xrtcdev->calibval &= RTC_CALIB_MASK;
+       writel(xrtcdev->calibval, (xrtcdev->reg_base + RTC_CALIB_WR));
 }
 
 static const struct rtc_class_ops xlnx_rtc_ops = {
@@ -174,7 +182,6 @@ static int xlnx_rtc_probe(struct platform_device *pdev)
        struct xlnx_rtc_dev *xrtcdev;
        struct resource *res;
        int ret;
-       unsigned int calibvalue;
 
        xrtcdev = devm_kzalloc(&pdev->dev, sizeof(*xrtcdev), GFP_KERNEL);
        if (!xrtcdev)
@@ -215,11 +222,11 @@ static int xlnx_rtc_probe(struct platform_device *pdev)
        }
 
        ret = of_property_read_u32(pdev->dev.of_node, "calibration",
-                                  &calibvalue);
+                                  &xrtcdev->calibval);
        if (ret)
-               calibvalue = RTC_CALIB_DEF;
+               xrtcdev->calibval = RTC_CALIB_DEF;
 
-       xlnx_init_rtc(xrtcdev, calibvalue);
+       xlnx_init_rtc(xrtcdev);
 
        device_init_wakeup(&pdev->dev, 1);