rtc: armada38x: reset after rtc power loss

When the RTC block looses power it needs a reset sequence to make it
usable again. Otherwise, writes to the time register have no effect.

This reset sequence combines information from the mvebu_rtc driver in
the Marvell provided U-Boot, and the SolidRun provided U-Boot repo.

Tested on the Armada 388 based SolidRun Clearfog Base.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Acked-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-armada38x.c b/drivers/rtc/rtc-armada38x.c
index 1e4978c..bde53c8 100644 (file)
--- a/drivers/rtc/rtc-armada38x.c
+++ b/drivers/rtc/rtc-armada38x.c
@@ -30,6 +30,8 @@
 #define RTC_IRQ_FREQ_1HZ           BIT(2)
 #define RTC_CCR                    0x18
 #define RTC_CCR_MODE               BIT(15)
+#define RTC_CONF_TEST      0x1C
+#define RTC_NOMINAL_TIMING         BIT(13)
 
 #define RTC_TIME           0xC
 #define RTC_ALARM1         0x10
@@ -75,6 +77,7 @@ struct armada38x_rtc {
        void __iomem        *regs_soc;
        spinlock_t          lock;
        int                 irq;
+       bool                initialized;
        struct value_to_freq *val_to_freq;
        struct armada38x_rtc_data *data;
 };
@@ -226,6 +229,23 @@ static int armada38x_rtc_read_time(struct device *dev, struct rtc_time *tm)
        return 0;
 }
 
+static void armada38x_rtc_reset(struct armada38x_rtc *rtc)
+{
+       u32 reg;
+
+       reg = rtc->data->read_rtc_reg(rtc, RTC_CONF_TEST);
+       /* If bits [7:0] are non-zero, assume RTC was uninitialized */
+       if (reg & 0xff) {
+               rtc_delayed_write(0, rtc, RTC_CONF_TEST);
+               msleep(500); /* Oscillator startup time */
+               rtc_delayed_write(0, rtc, RTC_TIME);
+               rtc_delayed_write(SOC_RTC_ALARM1 | SOC_RTC_ALARM2, rtc,
+                                 RTC_STATUS);
+               rtc_delayed_write(RTC_NOMINAL_TIMING, rtc, RTC_CCR);
+       }
+       rtc->initialized = true;
+}
+
 static int armada38x_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
        struct armada38x_rtc *rtc = dev_get_drvdata(dev);
@@ -237,6 +257,9 @@ static int armada38x_rtc_set_time(struct device *dev, struct rtc_time *tm)
        if (ret)
                goto out;
 
+       if (!rtc->initialized)
+               armada38x_rtc_reset(rtc);
+
        spin_lock_irqsave(&rtc->lock, flags);
        rtc_delayed_write(time, rtc, RTC_TIME);
        spin_unlock_irqrestore(&rtc->lock, flags);