watchdog: versal: Add support for Xilinx window watchdog

Add support for Xilinx window watchdog, which can be found on
Versal platforms.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Reviewed-by: Stefan Roese <sr@denx.de>

MAINTAINERS

@@ -447,6 +447,7 @@ M:	Michal Simek <michal.simek@xilinx.com>
 S:	Maintained
 T:	git https://gitlab.denx.de/u-boot/custodians/u-boot-microblaze.git
 F:	arch/arm/mach-versal/
+F:	drivers/watchdog/xilinx_wwdt.c
 N:	(?<!uni)versal
 
 ARM VERSATILE EXPRESS DRIVERS

drivers/watchdog/Kconfig

@@ -185,6 +185,15 @@ config XILINX_TB_WATCHDOG
 	  Select this to enable Xilinx Axi watchdog timer, which can be found on some
 	  Xilinx Microblaze Platforms.
 
+config WDT_XILINX
+	bool "Xilinx window watchdog timer support"
+	depends on WDT && ARCH_VERSAL
+	select REGMAP
+	imply WATCHDOG
+	help
+	  Select this to enable Xilinx window watchdog timer, which can be found on
+	  Xilinx Versal Platforms.
+
 config WDT_TANGIER
 	bool "Intel Tangier watchdog timer support"
 	depends on WDT && INTEL_MID

drivers/watchdog/Makefile

@@ -30,3 +30,4 @@ obj-$(CONFIG_WDT_OMAP3) += omap_wdt.o
 obj-$(CONFIG_WDT_SP805) += sp805_wdt.o
 obj-$(CONFIG_WDT_STM32MP) += stm32mp_wdt.o
 obj-$(CONFIG_WDT_TANGIER) += tangier_wdt.o
+obj-$(CONFIG_WDT_XILINX) += xilinx_wwdt.o

drivers/watchdog/xilinx_wwdt.c

@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Xilinx window watchdog timer driver.
+ *
+ * Author(s):	Michal Simek <michal.simek@xilinx.com>
+ *		Ashok Reddy Soma <ashokred@xilinx.com>
+ *
+ * Copyright (c) 2020, Xilinx Inc.
+ */
+
+#include <clk.h>
+#include <common.h>
+#include <dm.h>
+#include <regmap.h>
+#include <wdt.h>
+#include <linux/compat.h>
+#include <linux/io.h>
+
+/* Refresh Register Masks */
+#define XWT_WWREF_GWRR_MASK	BIT(0) /* Refresh and start new period */
+
+/* Generic Control/Status Register Masks */
+#define XWT_WWCSR_GWEN_MASK	BIT(0) /* Enable Bit */
+
+/* Register offsets for the Wdt device */
+#define XWT_WWREF_OFFSET	0x1000 /* Refresh Register */
+#define XWT_WWCSR_OFFSET	0x2000 /* Control/Status Register */
+#define XWT_WWOFF_OFFSET	0x2008 /* Offset Register */
+#define XWT_WWCMP0_OFFSET	0x2010 /* Compare Value Register0 */
+#define XWT_WWCMP1_OFFSET	0x2014 /* Compare Value Register1 */
+#define XWT_WWWRST_OFFSET	0x2FD0 /* Warm Reset Register */
+
+struct xlnx_wwdt_priv {
+	bool enable_once;
+	struct regmap *regs;
+	struct clk clk;
+};
+
+struct xlnx_wwdt_platdata {
+	bool enable_once;
+};
+
+static int xlnx_wwdt_reset(struct udevice *dev)
+{
+	struct xlnx_wwdt_priv *wdt = dev_get_priv(dev);
+
+	regmap_write(wdt->regs, XWT_WWREF_OFFSET, XWT_WWREF_GWRR_MASK);
+
+	return 0;
+}
+
+static int xlnx_wwdt_stop(struct udevice *dev)
+{
+	u32 csr;
+	struct xlnx_wwdt_priv *wdt = dev_get_priv(dev);
+
+	if (wdt->enable_once) {
+		dev_warn(dev, "Can't stop Xilinx watchdog.\n");
+		return -EBUSY;
+	}
+
+	/* Disable the generic watchdog timer */
+	regmap_read(wdt->regs, XWT_WWCSR_OFFSET, &csr);
+	csr &= ~(XWT_WWCSR_GWEN_MASK);
+	regmap_write(wdt->regs, XWT_WWCSR_OFFSET, csr);
+
+	clk_disable(&wdt->clk);
+
+	dev_dbg(dev, "Watchdog disabled!\n");
+
+	return 0;
+}
+
+static int xlnx_wwdt_start(struct udevice *dev, u64 timeout, ulong flags)
+{
+	int ret;
+	u32 csr;
+	u64 count;
+	unsigned long clock_f;
+	struct xlnx_wwdt_priv *wdt = dev_get_priv(dev);
+
+	clock_f = clk_get_rate(&wdt->clk);
+	if (IS_ERR_VALUE(clock_f)) {
+		dev_err(dev, "failed to get rate\n");
+		return clock_f;
+	}
+
+	dev_dbg(dev, "%s: CLK %ld\n", __func__, clock_f);
+
+	/* Calculate timeout count */
+	count = timeout * clock_f;
+
+	/* clk_enable will return -ENOSYS when it is not implemented */
+	ret = clk_enable(&wdt->clk);
+	if (ret && ret != -ENOSYS) {
+		dev_err(dev, "failed to enable clock\n");
+		return ret;
+	}
+
+	/*
+	 * Timeout count is half as there are two windows
+	 * first window overflow is ignored (interrupt),
+	 * reset is only generated at second window overflow
+	 */
+	count = count >> 1;
+
+	/* Disable the generic watchdog timer */
+	regmap_read(wdt->regs, XWT_WWCSR_OFFSET, &csr);
+	csr &= ~(XWT_WWCSR_GWEN_MASK);
+	regmap_write(wdt->regs, XWT_WWCSR_OFFSET, csr);
+
+	/* Set compare and offset registers for generic watchdog timeout */
+	regmap_write(wdt->regs, XWT_WWCMP0_OFFSET, (u32)count);
+	regmap_write(wdt->regs, XWT_WWCMP1_OFFSET, 0);
+	regmap_write(wdt->regs, XWT_WWOFF_OFFSET, (u32)count);
+
+	/* Enable the generic watchdog timer */
+	regmap_read(wdt->regs, XWT_WWCSR_OFFSET, &csr);
+	csr |= (XWT_WWCSR_GWEN_MASK);
+	regmap_write(wdt->regs, XWT_WWCSR_OFFSET, csr);
+
+	return 0;
+}
+
+static int xlnx_wwdt_probe(struct udevice *dev)
+{
+	int ret;
+	struct xlnx_wwdt_platdata *platdata = dev_get_platdata(dev);
+	struct xlnx_wwdt_priv *wdt = dev_get_priv(dev);
+
+	dev_dbg(dev, "%s: Probing wdt%u\n", __func__, dev->seq);
+
+	ret = regmap_init_mem(dev_ofnode(dev), &wdt->regs);
+	if (ret) {
+		dev_dbg(dev, "failed to get regbase of wwdt\n");
+		return ret;
+	}
+
+	wdt->enable_once = platdata->enable_once;
+
+	ret = clk_get_by_index(dev, 0, &wdt->clk);
+	if (ret < 0)
+		dev_err(dev, "failed to get clock\n");
+
+	return ret;
+}
+
+static int xlnx_wwdt_ofdata_to_platdata(struct udevice *dev)
+{
+	struct xlnx_wwdt_platdata *platdata = dev_get_platdata(dev);
+
+	platdata->enable_once = dev_read_u32_default(dev,
+						     "xlnx,wdt-enable-once", 0);
+	dev_dbg(dev, "wdt-enable-once %d\n", platdata->enable_once);
+
+	return 0;
+}
+
+static const struct wdt_ops xlnx_wwdt_ops = {
+	.start = xlnx_wwdt_start,
+	.reset = xlnx_wwdt_reset,
+	.stop = xlnx_wwdt_stop,
+};
+
+static const struct udevice_id xlnx_wwdt_ids[] = {
+	{ .compatible = "xlnx,versal-wwdt-1.0", },
+	{},
+};
+
+U_BOOT_DRIVER(xlnx_wwdt) = {
+	.name = "xlnx_wwdt",
+	.id = UCLASS_WDT,
+	.of_match = xlnx_wwdt_ids,
+	.probe = xlnx_wwdt_probe,
+	.priv_auto_alloc_size = sizeof(struct xlnx_wwdt_priv),
+	.platdata_auto_alloc_size = sizeof(struct xlnx_wwdt_platdata),
+	.ofdata_to_platdata = xlnx_wwdt_ofdata_to_platdata,
+	.ops = &xlnx_wwdt_ops,
+};