watchdog: xilinx_wwdt: Add Versal window watchdog support

Versal watchdog driver uses window watchdog mode. Window watchdog
timer(WWDT) contains closed(first) and open(second) window with
32 bit width. Write to the watchdog timer within predefined window
periods of time. This means a period that is not too soon and a
period that is not too late. The WWDT has to be restarted within
the open window time. If software tries to restart WWDT outside of
the open window time period, it generates a reset.

Signed-off-by: Srinivas Neeli <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called of_xilinx_wdt.
 
+config XILINX_WINDOW_WATCHDOG
+	tristate "Xilinx window watchdog timer"
+	depends on HAS_IOMEM
+	depends on ARM64
+	select WATCHDOG_CORE
+	help
+	  Window watchdog driver for the versal_wwdt IP core.
+	  Window watchdog timer(WWDT) contains closed(first) and
+	  open(second) window with 32 bit width. Write to the watchdog
+	  timer within predefined window periods of time. This means
+	  a period that is not too soon and a period that is not too
+	  late. The WWDT has to be restarted within the open window time.
+	  If software tries to restart WWDT outside of the open window
+	  time period, it generates a reset.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called xilinx_wwdt.
+
 config ZIIRAVE_WATCHDOG
 	tristate "Zodiac RAVE Watchdog Timer"
 	depends on I2C

drivers/watchdog/Makefile

···
 
 # MicroBlaze Architecture
 obj-$(CONFIG_XILINX_WATCHDOG) += of_xilinx_wdt.o
+obj-$(CONFIG_XILINX_WINDOW_WATCHDOG) += xilinx_wwdt.o
 
 # MIPS Architecture
 obj-$(CONFIG_ATH79_WDT) += ath79_wdt.o

drivers/watchdog/xilinx_wwdt.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Window watchdog device driver for Xilinx Versal WWDT
+ *
+ * Copyright (C) 2022 - 2023, Advanced Micro Devices, Inc.
+ */
+
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of_address.h>
+#include <linux/watchdog.h>
+
+/* Max timeout is calculated at 100MHz source clock */
+#define XWWDT_DEFAULT_TIMEOUT	42
+#define XWWDT_MIN_TIMEOUT	1
+
+/* Register offsets for the WWDT device */
+#define XWWDT_MWR_OFFSET	0x00
+#define XWWDT_ESR_OFFSET	0x04
+#define XWWDT_FCR_OFFSET	0x08
+#define XWWDT_FWR_OFFSET	0x0c
+#define XWWDT_SWR_OFFSET	0x10
+
+/* Master Write Control Register Masks */
+#define XWWDT_MWR_MASK		BIT(0)
+
+/* Enable and Status Register Masks */
+#define XWWDT_ESR_WINT_MASK	BIT(16)
+#define XWWDT_ESR_WSW_MASK	BIT(8)
+#define XWWDT_ESR_WEN_MASK	BIT(0)
+
+#define XWWDT_CLOSE_WINDOW_PERCENT	50
+
+static int wwdt_timeout;
+static int closed_window_percent;
+
+module_param(wwdt_timeout, int, 0);
+MODULE_PARM_DESC(wwdt_timeout,
+		 "Watchdog time in seconds. (default="
+		 __MODULE_STRING(XWWDT_DEFAULT_TIMEOUT) ")");
+module_param(closed_window_percent, int, 0);
+MODULE_PARM_DESC(closed_window_percent,
+		 "Watchdog closed window percentage. (default="
+		 __MODULE_STRING(XWWDT_CLOSE_WINDOW_PERCENT) ")");
+/**
+ * struct xwwdt_device - Watchdog device structure
+ * @base: base io address of WDT device
+ * @spinlock: spinlock for IO register access
+ * @xilinx_wwdt_wdd: watchdog device structure
+ * @freq: source clock frequency of WWDT
+ * @close_percent: Closed window percent
+ */
+struct xwwdt_device {
+	void __iomem *base;
+	spinlock_t spinlock; /* spinlock for register handling */
+	struct watchdog_device xilinx_wwdt_wdd;
+	unsigned long freq;
+	u32 close_percent;
+};
+
+static int xilinx_wwdt_start(struct watchdog_device *wdd)
+{
+	struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
+	struct watchdog_device *xilinx_wwdt_wdd = &xdev->xilinx_wwdt_wdd;
+	u64 time_out, closed_timeout, open_timeout;
+	u32 control_status_reg;
+
+	/* Calculate timeout count */
+	time_out = xdev->freq * wdd->timeout;
+	closed_timeout = (time_out * xdev->close_percent) / 100;
+	open_timeout = time_out - closed_timeout;
+	wdd->min_hw_heartbeat_ms = xdev->close_percent * 10 * wdd->timeout;
+
+	spin_lock(&xdev->spinlock);
+
+	iowrite32(XWWDT_MWR_MASK, xdev->base + XWWDT_MWR_OFFSET);
+	iowrite32(~(u32)XWWDT_ESR_WEN_MASK, xdev->base + XWWDT_ESR_OFFSET);
+	iowrite32((u32)closed_timeout, xdev->base + XWWDT_FWR_OFFSET);
+	iowrite32((u32)open_timeout, xdev->base + XWWDT_SWR_OFFSET);
+
+	/* Enable the window watchdog timer */
+	control_status_reg = ioread32(xdev->base + XWWDT_ESR_OFFSET);
+	control_status_reg |= XWWDT_ESR_WEN_MASK;
+	iowrite32(control_status_reg, xdev->base + XWWDT_ESR_OFFSET);
+
+	spin_unlock(&xdev->spinlock);
+
+	dev_dbg(xilinx_wwdt_wdd->parent, "Watchdog Started!\n");
+
+	return 0;
+}
+
+static int xilinx_wwdt_keepalive(struct watchdog_device *wdd)
+{
+	struct xwwdt_device *xdev = watchdog_get_drvdata(wdd);
+	u32 control_status_reg;
+
+	spin_lock(&xdev->spinlock);
+
+	/* Enable write access control bit for the window watchdog */
+	iowrite32(XWWDT_MWR_MASK, xdev->base + XWWDT_MWR_OFFSET);
+
+	/* Trigger restart kick to watchdog */
+	control_status_reg = ioread32(xdev->base + XWWDT_ESR_OFFSET);
+	control_status_reg |= XWWDT_ESR_WSW_MASK;
+	iowrite32(control_status_reg, xdev->base + XWWDT_ESR_OFFSET);
+
+	spin_unlock(&xdev->spinlock);
+
+	return 0;
+}
+
+static const struct watchdog_info xilinx_wwdt_ident = {
+	.options = WDIOF_KEEPALIVEPING |
+		WDIOF_SETTIMEOUT,
+	.firmware_version = 1,
+	.identity = "xlnx_window watchdog",
+};
+
+static const struct watchdog_ops xilinx_wwdt_ops = {
+	.owner = THIS_MODULE,
+	.start = xilinx_wwdt_start,
+	.ping = xilinx_wwdt_keepalive,
+};
+
+static int xwwdt_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *xilinx_wwdt_wdd;
+	struct device *dev = &pdev->dev;
+	struct xwwdt_device *xdev;
+	struct clk *clk;
+	int ret;
+
+	xdev = devm_kzalloc(dev, sizeof(*xdev), GFP_KERNEL);
+	if (!xdev)
+		return -ENOMEM;
+
+	xilinx_wwdt_wdd = &xdev->xilinx_wwdt_wdd;
+	xilinx_wwdt_wdd->info = &xilinx_wwdt_ident;
+	xilinx_wwdt_wdd->ops = &xilinx_wwdt_ops;
+	xilinx_wwdt_wdd->parent = dev;
+
+	xdev->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(xdev->base))
+		return PTR_ERR(xdev->base);
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	xdev->freq = clk_get_rate(clk);
+	if (!xdev->freq)
+		return -EINVAL;
+
+	xilinx_wwdt_wdd->min_timeout = XWWDT_MIN_TIMEOUT;
+	xilinx_wwdt_wdd->timeout = XWWDT_DEFAULT_TIMEOUT;
+	xilinx_wwdt_wdd->max_hw_heartbeat_ms = 1000 * xilinx_wwdt_wdd->timeout;
+
+	if (closed_window_percent == 0 || closed_window_percent >= 100)
+		xdev->close_percent = XWWDT_CLOSE_WINDOW_PERCENT;
+	else
+		xdev->close_percent = closed_window_percent;
+
+	watchdog_init_timeout(xilinx_wwdt_wdd, wwdt_timeout, &pdev->dev);
+	spin_lock_init(&xdev->spinlock);
+	watchdog_set_drvdata(xilinx_wwdt_wdd, xdev);
+	watchdog_set_nowayout(xilinx_wwdt_wdd, 1);
+
+	ret = devm_watchdog_register_device(dev, xilinx_wwdt_wdd);
+	if (ret)
+		return ret;
+
+	dev_info(dev, "Xilinx window watchdog Timer with timeout %ds\n",
+		 xilinx_wwdt_wdd->timeout);
+
+	return 0;
+}
+
+static const struct of_device_id xwwdt_of_match[] = {
+	{ .compatible = "xlnx,versal-wwdt", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, xwwdt_of_match);
+
+static struct platform_driver xwwdt_driver = {
+	.probe = xwwdt_probe,
+	.driver = {
+		.name = "Xilinx window watchdog",
+		.of_match_table = xwwdt_of_match,
+	},
+};
+
+module_platform_driver(xwwdt_driver);
+
+MODULE_AUTHOR("Neeli Srinivas <[e-mail]>");
+MODULE_DESCRIPTION("Xilinx window watchdog driver");
+MODULE_LICENSE("GPL");