watchdog: Add Cadence watchdog driver

This IP can be found on Zynq and ZynqMP devices.
The driver was tested with reset-on-timeout; feature.

Also adding WATCHDOG symbol to Kconfig because it is required.

Signed-off-by: Shreenidhi Shedi <imshedi@gmail.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

drivers/watchdog/Kconfig

@@ -1,5 +1,13 @@
 menu "Watchdog Timer Support"
 
+config WATCHDOG
+	bool "Enable U-Boot watchdog reset"
+	help
+	  This option enables U-Boot watchdog support where U-Boot is using
+	  watchdog_reset function to service watchdog device in U-Boot. Enable
+	  this option if you want to service enabled watchdog by U-Boot. Disable
+	  this option if you want U-Boot to start watchdog but never service it.
+
 config HW_WATCHDOG
 	bool
 
@@ -78,4 +86,12 @@ config WDT_ORION
 	   Select this to enable Orion watchdog timer, which can be found on some
 	   Marvell Armada chips.
 
+config WDT_CDNS
+	bool "Cadence watchdog timer support"
+	depends on WDT
+	imply WATCHDOG
+	help
+	   Select this to enable Cadence watchdog timer, which can be found on some
+	   Xilinx Microzed Platform.
+
 endmenu

drivers/watchdog/Makefile

@@ -22,3 +22,4 @@ obj-$(CONFIG_WDT_ASPEED) += ast_wdt.o
 obj-$(CONFIG_WDT_BCM6345) += bcm6345_wdt.o
 obj-$(CONFIG_BCM2835_WDT)       += bcm2835_wdt.o
 obj-$(CONFIG_WDT_ORION) += orion_wdt.o
+obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o

drivers/watchdog/cdns_wdt.c

@@ -0,0 +1,276 @@
+/*
+ * Cadence WDT driver - Used by Xilinx Zynq
+ * Reference: Linux kernel Cadence watchdog driver.
+ *
+ * Author(s):	Shreenidhi Shedi <yesshedi@gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <wdt.h>
+#include <clk.h>
+#include <linux/io.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct cdns_regs {
+	u32 zmr;	/* WD Zero mode register, offset - 0x0 */
+	u32 ccr;	/* Counter Control Register offset - 0x4 */
+	u32 restart;	/* Restart key register, offset - 0x8 */
+	u32 status;	/* Status Register, offset - 0xC */
+};
+
+struct cdns_wdt_priv {
+	bool rst;
+	u32 timeout;
+	void __iomem *reg;
+	struct cdns_regs *regs;
+};
+
+#define CDNS_WDT_DEFAULT_TIMEOUT	10
+
+/* Supports 1 - 516 sec */
+#define CDNS_WDT_MIN_TIMEOUT		1
+#define CDNS_WDT_MAX_TIMEOUT		516
+
+/* Restart key */
+#define CDNS_WDT_RESTART_KEY		0x00001999
+
+/* Counter register access key */
+#define CDNS_WDT_REGISTER_ACCESS_KEY	0x00920000
+
+/* Counter value divisor */
+#define CDNS_WDT_COUNTER_VALUE_DIVISOR	0x1000
+
+/* Clock prescaler value and selection */
+#define CDNS_WDT_PRESCALE_64		64
+#define CDNS_WDT_PRESCALE_512		512
+#define CDNS_WDT_PRESCALE_4096		4096
+#define CDNS_WDT_PRESCALE_SELECT_64	1
+#define CDNS_WDT_PRESCALE_SELECT_512	2
+#define CDNS_WDT_PRESCALE_SELECT_4096	3
+
+/* Input clock frequency */
+#define CDNS_WDT_CLK_75MHZ	75000000
+
+/* Counter maximum value */
+#define CDNS_WDT_COUNTER_MAX	0xFFF
+
+/*********************    Register Map    **********************************/
+
+/*
+ * Zero Mode Register - This register controls how the time out is indicated
+ * and also contains the access code to allow writes to the register (0xABC).
+ */
+#define CDNS_WDT_ZMR_WDEN_MASK	0x00000001 /* Enable the WDT */
+#define CDNS_WDT_ZMR_RSTEN_MASK	0x00000002 /* Enable the reset output */
+#define CDNS_WDT_ZMR_IRQEN_MASK	0x00000004 /* Enable IRQ output */
+#define CDNS_WDT_ZMR_RSTLEN_16	0x00000030 /* Reset pulse of 16 pclk cycles */
+#define CDNS_WDT_ZMR_ZKEY_VAL	0x00ABC000 /* Access key, 0xABC << 12 */
+
+/*
+ * Counter Control register - This register controls how fast the timer runs
+ * and the reset value and also contains the access code to allow writes to
+ * the register.
+ */
+#define CDNS_WDT_CCR_CRV_MASK	0x00003FFC /* Counter reset value */
+
+/* Write access to Registers */
+static inline void cdns_wdt_writereg(u32 *addr, u32 val)
+{
+	writel(val, addr);
+}
+
+/**
+ * cdns_wdt_reset - Reload the watchdog timer (i.e. pat the watchdog).
+ *
+ * @dev: Watchdog device
+ *
+ * Write the restart key value (0x00001999) to the restart register.
+ *
+ * Return: Always 0
+ */
+static int cdns_wdt_reset(struct udevice *dev)
+{
+	struct cdns_wdt_priv *priv = dev_get_priv(dev);
+
+	debug("%s\n", __func__);
+
+	cdns_wdt_writereg(&priv->regs->restart, CDNS_WDT_RESTART_KEY);
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_start - Enable and start the watchdog.
+ *
+ * @dev: Watchdog device
+ * @timeout: Timeout value
+ * @flags: Driver flags
+ *
+ * The counter value is calculated according to the formula:
+ *		count = (timeout * clock) / prescaler + 1.
+ *
+ * The calculated count is divided by 0x1000 to obtain the field value
+ * to write to counter control register.
+ *
+ * Clears the contents of prescaler and counter reset value. Sets the
+ * prescaler to 4096 and the calculated count and access key
+ * to write to CCR Register.
+ *
+ * Sets the WDT (WDEN bit) and either the Reset signal(RSTEN bit)
+ * or Interrupt signal(IRQEN) with a specified cycles and the access
+ * key to write to ZMR Register.
+ *
+ * Return: Upon success 0, failure -1.
+ */
+static int cdns_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
+{
+	ulong clk_f;
+	u32 count, prescaler, ctrl_clksel, data = 0;
+	struct clk clock;
+	struct cdns_wdt_priv *priv = dev_get_priv(dev);
+
+	if (clk_get_by_index(dev, 0, &clock) < 0) {
+		dev_err(dev, "failed to get clock\n");
+		return -1;
+	}
+
+	clk_f = clk_get_rate(&clock);
+	if (IS_ERR_VALUE(clk_f)) {
+		dev_err(dev, "failed to get rate\n");
+		return -1;
+	}
+
+	debug("%s: CLK_FREQ %ld, timeout %lld\n", __func__, clk_f, timeout);
+
+	if ((timeout < CDNS_WDT_MIN_TIMEOUT) ||
+	    (timeout > CDNS_WDT_MAX_TIMEOUT)) {
+		timeout = priv->timeout;
+	}
+
+	if (clk_f <= CDNS_WDT_CLK_75MHZ) {
+		prescaler = CDNS_WDT_PRESCALE_512;
+		ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
+	} else {
+		prescaler = CDNS_WDT_PRESCALE_4096;
+		ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
+	}
+
+	/*
+	 * Counter value divisor to obtain the value of
+	 * counter reset to be written to control register.
+	 */
+	count = (timeout * (clk_f / prescaler)) /
+		CDNS_WDT_COUNTER_VALUE_DIVISOR + 1;
+
+	if (count > CDNS_WDT_COUNTER_MAX)
+		count = CDNS_WDT_COUNTER_MAX;
+
+	cdns_wdt_writereg(&priv->regs->zmr, CDNS_WDT_ZMR_ZKEY_VAL);
+
+	count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;
+
+	/* Write counter access key first to be able write to register */
+	data = count | CDNS_WDT_REGISTER_ACCESS_KEY | ctrl_clksel;
+	cdns_wdt_writereg(&priv->regs->ccr, data);
+
+	data = CDNS_WDT_ZMR_WDEN_MASK | CDNS_WDT_ZMR_RSTLEN_16 |
+		CDNS_WDT_ZMR_ZKEY_VAL;
+
+	/* Reset on timeout if specified in device tree. */
+	if (priv->rst) {
+		data |= CDNS_WDT_ZMR_RSTEN_MASK;
+		data &= ~CDNS_WDT_ZMR_IRQEN_MASK;
+	} else {
+		data &= ~CDNS_WDT_ZMR_RSTEN_MASK;
+		data |= CDNS_WDT_ZMR_IRQEN_MASK;
+	}
+
+	cdns_wdt_writereg(&priv->regs->zmr, data);
+	cdns_wdt_writereg(&priv->regs->restart, CDNS_WDT_RESTART_KEY);
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_stop - Stop the watchdog.
+ *
+ * @dev: Watchdog device
+ *
+ * Read the contents of the ZMR register, clear the WDEN bit in the register
+ * and set the access key for successful write.
+ *
+ * Return: Always 0
+ */
+static int cdns_wdt_stop(struct udevice *dev)
+{
+	struct cdns_wdt_priv *priv = dev_get_priv(dev);
+
+	cdns_wdt_writereg(&priv->regs->zmr,
+			  CDNS_WDT_ZMR_ZKEY_VAL & (~CDNS_WDT_ZMR_WDEN_MASK));
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_probe - Probe call for the device.
+ *
+ * @dev: Handle to the udevice structure.
+ *
+ * Return: Always 0.
+ */
+static int cdns_wdt_probe(struct udevice *dev)
+{
+	struct cdns_wdt_priv *priv = dev_get_priv(dev);
+
+	debug("%s: Probing wdt%u\n", __func__, dev->seq);
+
+	priv->reg = ioremap((u32)priv->regs, sizeof(struct cdns_regs));
+
+	cdns_wdt_stop(dev);
+
+	return 0;
+}
+
+static int cdns_wdt_ofdata_to_platdata(struct udevice *dev)
+{
+	int node = dev_of_offset(dev);
+	struct cdns_wdt_priv *priv = dev_get_priv(dev);
+
+	priv->regs = devfdt_get_addr_ptr(dev);
+	if (IS_ERR(priv->regs))
+		return PTR_ERR(priv->regs);
+
+	priv->timeout = fdtdec_get_int(gd->fdt_blob, node, "timeout-sec",
+				       CDNS_WDT_DEFAULT_TIMEOUT);
+
+	priv->rst = fdtdec_get_bool(gd->fdt_blob, node, "reset-on-timeout");
+
+	debug("%s: timeout %d, reset %d\n", __func__, priv->timeout, priv->rst);
+
+	return 0;
+}
+
+static const struct wdt_ops cdns_wdt_ops = {
+	.start = cdns_wdt_start,
+	.reset = cdns_wdt_reset,
+	.stop = cdns_wdt_stop,
+};
+
+static const struct udevice_id cdns_wdt_ids[] = {
+	{ .compatible = "cdns,wdt-r1p2" },
+	{}
+};
+
+U_BOOT_DRIVER(cdns_wdt) = {
+	.name = "cdns_wdt",
+	.id = UCLASS_WDT,
+	.of_match = cdns_wdt_ids,
+	.probe = cdns_wdt_probe,
+	.priv_auto_alloc_size = sizeof(struct cdns_wdt_priv),
+	.ofdata_to_platdata = cdns_wdt_ofdata_to_platdata,
+	.ops = &cdns_wdt_ops,
+};