Some boards like the Turris Omnia have an RTC chip that does not get
initialized. Initializing the RTC at the driver level helps get rid of
bootloader hacks that write special register values.

--- a/drivers/rtc/rtc-armada38x.c
+++ b/drivers/rtc/rtc-armada38x.c
@@ -30,6 +30,9 @@
 #define RTC_IRQ_FREQ_1HZ	    BIT(2)
 #define RTC_CCR		    0x18
 #define RTC_CCR_MODE		    BIT(15)
+#define RTC_CCR_NORMAL_PPB	    0x2000
+#define RTC_TEST_CONF		    0x1c
+#define RTC_TEST_CONF_MASK	    0xff
 
 #define RTC_TIME	    0xC
 #define RTC_ALARM1	    0x10
@@ -91,6 +94,7 @@ struct armada38x_rtc_data {
 	void (*clear_isr)(struct armada38x_rtc *rtc);
 	void (*unmask_interrupt)(struct armada38x_rtc *rtc);
 	u32 alarm;
+	void (*init_rtc)(struct armada38x_rtc *rtc);
 };
 
 /*
@@ -202,6 +206,23 @@ static void armada38x_unmask_interrupt(s
 	writel(val | SOC_RTC_ALARM1_MASK, rtc->regs_soc + SOC_RTC_INTERRUPT);
 }
 
+static void armada38x_rtc_init(struct armada38x_rtc *rtc)
+{
+	u32 reg;
+
+	/* Test RTC test configuration register bits [7:0] */
+	reg = readl(rtc->regs + RTC_TEST_CONF);
+	/* If bits [7:0] are non-zero, assume RTC was uninitialized */
+	if (reg & RTC_TEST_CONF_MASK) {
+		rtc_delayed_write(0, rtc, RTC_TEST_CONF);
+		rtc_delayed_write(0, rtc, RTC_TIME);
+		rtc_delayed_write((RTC_STATUS_ALARM1 | RTC_STATUS_ALARM2),
+				rtc, RTC_STATUS);
+		rtc_delayed_write(RTC_CCR_NORMAL_PPB, rtc, RTC_CCR);
+	}
+	return;
+}
+
 static void armada8k_clear_isr(struct armada38x_rtc *rtc)
 {
 	writel(RTC_8K_ALARM2, rtc->regs_soc + RTC_8K_ISR);
@@ -464,6 +485,7 @@ static const struct armada38x_rtc_data a
 	.clear_isr = armada38x_clear_isr,
 	.unmask_interrupt = armada38x_unmask_interrupt,
 	.alarm = ALARM1,
+	.init_rtc = armada38x_rtc_init,
 };
 
 static const struct armada38x_rtc_data armada8k_data = {
@@ -558,6 +580,16 @@ static __init int armada38x_rtc_probe(st
 	if (ret)
 		dev_err(&pdev->dev, "Failed to register RTC device: %d\n", ret);
 
+	/*
+	 * Try to detect if RTC is in uninitialized state.
+	 * It is not definitive to know if the RTC is in an uninialized state or not,
+	 * but the following call will read some bits in the RTC unit and guess if
+	 * if it's in that state, and accordingly set it to sane default values.
+	 */
+	else if (rtc->data->init_rtc) {
+		rtc->data->init_rtc(rtc);
+	}
+
 	return ret;
 }
 
