rtc: zynqmp: Add support for ZynqMP RTC

The whole driver logic is taken from Linux kernel but only set/get/reset
functions are implemented. When device is power off RTC is power out of
battery.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

MAINTAINERS

@@ -600,6 +600,7 @@ F:	drivers/mtd/nand/raw/zynq_nand.c
 F:	drivers/net/phy/xilinx_phy.c
 F:	drivers/net/zynq_gem.c
 F:	drivers/serial/serial_zynq.c
+F:	drivers/rtc/zynqmp_rtc.c
 F:	drivers/spi/zynq_qspi.c
 F:	drivers/spi/zynq_spi.c
 F:	drivers/timer/cadence-ttc.c

drivers/rtc/Kconfig

@@ -195,4 +195,11 @@ config RTC_DAVINCI
 	  Say "yes" here to support the on chip real time clock
 	  present on TI OMAP1, AM33xx, DA8xx/OMAP-L13x, AM43xx and DRA7xx.
 
+config RTC_ZYNQMP
+	bool "Enable ZynqMP RTC driver"
+	depends on ARCH_ZYNQMP
+	help
+	  Say "yes" here to support the on chip real time clock
+	  present on Xilinx ZynqMP SoC.
+
 endmenu

drivers/rtc/Makefile

@@ -57,3 +57,4 @@ obj-$(CONFIG_RTC_STM32) += stm32_rtc.o
 obj-$(CONFIG_SANDBOX) += sandbox_rtc.o
 obj-$(CONFIG_RTC_X1205) += x1205.o
 obj-$(CONFIG_RTC_ABX80X) += abx80x.o
+obj-$(CONFIG_RTC_ZYNQMP) += zynqmp_rtc.o

drivers/rtc/zynqmp_rtc.c

@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021, Xilinx, Inc.
+ */
+
+#define LOG_CATEGORY UCLASS_RTC
+
+#include <common.h>
+#include <dm.h>
+#include <rtc.h>
+#include <asm/io.h>
+
+/* RTC Registers */
+#define RTC_SET_TM_WR		0x00
+#define RTC_SET_TM_RD		0x04
+#define RTC_CALIB_WR		0x08
+#define RTC_CUR_TM		0x10
+#define RTC_INT_STS		0x20
+#define RTC_CTRL		0x40
+
+#define RTC_INT_SEC		BIT(0)
+#define RTC_BATT_EN		BIT(31)
+#define RTC_CALIB_DEF		0x198233
+#define RTC_CALIB_MASK		0x1FFFFF
+
+struct zynqmp_rtc_priv {
+	fdt_addr_t	base;
+	unsigned int	calibval;
+};
+
+static int zynqmp_rtc_get(struct udevice *dev, struct rtc_time *tm)
+{
+	struct zynqmp_rtc_priv *priv = dev_get_priv(dev);
+	u32 status;
+	unsigned long read_time;
+
+	status = readl(priv->base + RTC_INT_STS);
+
+	if (status & RTC_INT_SEC) {
+		/*
+		 * RTC has updated the CURRENT_TIME with the time written into
+		 * SET_TIME_WRITE register.
+		 */
+		read_time = readl(priv->base + RTC_CUR_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(priv->base + RTC_SET_TM_RD) - 1;
+	}
+
+	rtc_to_tm(read_time, tm);
+
+	return 0;
+}
+
+static int zynqmp_rtc_set(struct udevice *dev, const struct rtc_time *tm)
+{
+	struct zynqmp_rtc_priv *priv = dev_get_priv(dev);
+	unsigned long new_time = 0;
+
+	if (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_mktime(tm) + 1;
+
+	/*
+	 * Writing into calibration register will clear the Tick Counter and
+	 * force the next second to be signaled exactly in 1 second period
+	 */
+	priv->calibval &= RTC_CALIB_MASK;
+	writel(priv->calibval, (priv->base + RTC_CALIB_WR));
+
+	writel(new_time, priv->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, priv->base + RTC_INT_STS);
+
+	return 0;
+}
+
+static int zynqmp_rtc_reset(struct udevice *dev)
+{
+	return zynqmp_rtc_set(dev, NULL);
+}
+
+static int zynqmp_rtc_init(struct udevice *dev)
+{
+	struct zynqmp_rtc_priv *priv = dev_get_priv(dev);
+	u32 rtc_ctrl;
+
+	/* Enable RTC switch to battery when VCC_PSAUX is not available */
+	rtc_ctrl = readl(priv->base + RTC_CTRL);
+	rtc_ctrl |= RTC_BATT_EN;
+	writel(rtc_ctrl, priv->base + RTC_CTRL);
+
+	/*
+	 * Based on crystal freq of 33.330 KHz
+	 * set the seconds counter and enable, set fractions counter
+	 * to default value suggested as per design spec
+	 * to correct RTC delay in frequency over period of time.
+	 */
+	priv->calibval &= RTC_CALIB_MASK;
+	writel(priv->calibval, (priv->base + RTC_CALIB_WR));
+
+	return 0;
+}
+
+static int zynqmp_rtc_probe(struct udevice *dev)
+{
+	struct zynqmp_rtc_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	priv->base = dev_read_addr(dev);
+	if (priv->base == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	priv->calibval = dev_read_u32_default(dev, "calibration",
+					      RTC_CALIB_DEF);
+
+	ret = zynqmp_rtc_init(dev);
+
+	return ret;
+}
+
+static const struct rtc_ops zynqmp_rtc_ops = {
+	.get = zynqmp_rtc_get,
+	.set = zynqmp_rtc_set,
+	.reset = zynqmp_rtc_reset,
+};
+
+static const struct udevice_id zynqmp_rtc_ids[] = {
+	{ .compatible = "xlnx,zynqmp-rtc" },
+	{ }
+};
+
+U_BOOT_DRIVER(rtc_zynqmp) = {
+	.name = "rtc-zynqmp",
+	.id = UCLASS_RTC,
+	.probe = zynqmp_rtc_probe,
+	.of_match = zynqmp_rtc_ids,
+	.ops = &zynqmp_rtc_ops,
+	.priv_auto = sizeof(struct zynqmp_rtc_priv),
+};