[v3,05/10] watchdog: ROHM BD96801 PMIC WDG driver

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 85eea38dbdf4..ceb3431f23b8 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -181,6 +181,19 @@  config BD957XMUF_WATCHDOG
 	  watchdog. Alternatively say M to compile the driver as a module,
 	  which will be called bd9576_wdt.
 
+config BD96801_WATCHDOG
+	tristate "ROHM BD96801 PMIC Watchdog"
+	depends on MFD_ROHM_BD96801
+	select WATCHDOG_CORE
+	help
+	  Support for the watchdog in the ROHM BD96801 PMIC. Watchdog can be
+	  configured to only generate IRQ or to trigger system reset via reset
+	  pin.
+
+	  Say Y here to include support for the ROHM BD96801 watchdog.
+	  Alternatively say M to compile the driver as a module,
+	  which will be called bd96801_wdt.
+
 config CROS_EC_WATCHDOG
 	tristate "ChromeOS EC-based watchdog"
 	select WATCHDOG_CORE
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2d1117564f5b..b51030f035a6 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -218,6 +218,7 @@  obj-$(CONFIG_XEN_WDT) += xen_wdt.o
 
 # Architecture Independent
 obj-$(CONFIG_BD957XMUF_WATCHDOG) += bd9576_wdt.o
+obj-$(CONFIG_BD96801_WATCHDOG) += bd96801_wdt.o
 obj-$(CONFIG_CROS_EC_WATCHDOG) += cros_ec_wdt.o
 obj-$(CONFIG_DA9052_WATCHDOG) += da9052_wdt.o
 obj-$(CONFIG_DA9055_WATCHDOG) += da9055_wdt.o
diff --git a/drivers/watchdog/bd96801_wdt.c b/drivers/watchdog/bd96801_wdt.c
new file mode 100644
index 000000000000..ff51f42ced2a
--- /dev/null
+++ b/drivers/watchdog/bd96801_wdt.c
@@ -0,0 +1,416 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 ROHM Semiconductors
+ *
+ * ROHM BD96801 watchdog driver
+ */
+
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/rohm-bd96801.h>
+#include <linux/mfd/rohm-generic.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+#include <linux/watchdog.h>
+
+static bool nowayout;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout,
+		"Watchdog cannot be stopped once started (default=\"false\")");
+
+#define BD96801_WD_TMO_SHORT_MASK	0x70
+#define BD96801_WD_RATIO_MASK		0x3
+#define BD96801_WD_TYPE_MASK		0x4
+#define BD96801_WD_TYPE_SLOW		0x4
+#define BD96801_WD_TYPE_WIN		0x0
+
+#define BD96801_WD_EN_MASK		0x3
+#define BD96801_WD_IF_EN		0x1
+#define BD96801_WD_QA_EN		0x2
+#define BD96801_WD_DISABLE		0x0
+
+#define BD96801_WD_ASSERT_MASK		0x8
+#define BD96801_WD_ASSERT_RST		0x8
+#define BD96801_WD_ASSERT_IRQ		0x0
+
+#define BD96801_WD_FEED_MASK		0x1
+#define BD96801_WD_FEED			0x1
+
+/* 1.1 mS */
+#define FASTNG_MIN			11
+#define FASTNG_MAX_US			(100 * FASTNG_MIN << 7)
+#define SLOWNG_MAX_US			(16 * FASTNG_MAX_US)
+
+#define BD96801_WDT_DEFAULT_MARGIN_MS	1843
+/* Unit is seconds */
+#define DEFAULT_TIMEOUT 30
+
+/*
+ * BD96801 WDG supports window mode so the TMO consists of SHORT and LONG
+ * timeout values. SHORT time is meaningful only in window mode where feeding
+ * period shorter than SHORT would be an error. LONG time is used to detect if
+ * feeding is not occurring within given time limit (SoC SW hangs). The LONG
+ * timeout time is a multiple of (2, 4, 8 or 16 times) the SHORT timeout.
+ */
+
+struct wdtbd96801 {
+	struct device		*dev;
+	struct regmap		*regmap;
+	struct watchdog_device	wdt;
+};
+
+static int bd96801_wdt_ping(struct watchdog_device *wdt)
+{
+	struct wdtbd96801 *w = watchdog_get_drvdata(wdt);
+
+	return regmap_update_bits(w->regmap, BD96801_REG_WD_FEED,
+				  BD96801_WD_FEED_MASK, BD96801_WD_FEED);
+}
+
+static int bd96801_wdt_start(struct watchdog_device *wdt)
+{
+	struct wdtbd96801 *w = watchdog_get_drvdata(wdt);
+
+	return regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
+				  BD96801_WD_EN_MASK, BD96801_WD_IF_EN);
+}
+
+static int bd96801_wdt_stop(struct watchdog_device *wdt)
+{
+	struct wdtbd96801 *w = watchdog_get_drvdata(wdt);
+
+	return regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
+				  BD96801_WD_EN_MASK, BD96801_WD_DISABLE);
+}
+
+static const struct watchdog_info bd96801_wdt_info = {
+	.options	= WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
+			  WDIOF_SETTIMEOUT,
+	.identity	= "BD96801 Watchdog",
+};
+
+static const struct watchdog_ops bd96801_wdt_ops = {
+	.start		= bd96801_wdt_start,
+	.stop		= bd96801_wdt_stop,
+	.ping		= bd96801_wdt_ping,
+};
+
+static int find_closest_fast(unsigned int target, int *sel, unsigned int *val)
+{
+	unsigned int window = FASTNG_MIN;
+	int i;
+
+	for (i = 0; i < 8 && window < target; i++)
+		window <<= 1;
+
+	if (i == 8)
+		return -EINVAL;
+
+	*val = window;
+	*sel = i;
+
+	return 0;
+}
+
+static int find_closest_slow_by_fast(unsigned int fast_val, unsigned int *target,
+				     int *slowsel)
+{
+	static const int multipliers[] = {2, 4, 8, 16};
+	int sel;
+
+	for (sel = 0; sel < ARRAY_SIZE(multipliers) &&
+	     multipliers[sel] * fast_val < *target; sel++)
+		;
+
+	if (sel == ARRAY_SIZE(multipliers))
+		return -EINVAL;
+
+	*slowsel = sel;
+	*target = multipliers[sel] * fast_val;
+
+	return 0;
+}
+
+static int find_closest_slow(unsigned int *target, int *slow_sel, int *fast_sel)
+{
+	static const int multipliers[] = {2, 4, 8, 16};
+	unsigned int window = FASTNG_MIN;
+	unsigned int val = 0;
+	int i, j;
+
+	for (i = 0; i < 8; i++) {
+		for (j = 0; j < ARRAY_SIZE(multipliers); j++) {
+			unsigned int slow;
+
+			slow = window * multipliers[j];
+			if (slow >= *target && (!val || slow < val)) {
+				val = slow;
+				*fast_sel = i;
+				*slow_sel = j;
+			}
+		}
+		window <<= 1;
+	}
+	if (!val)
+		return -EINVAL;
+
+	*target = val;
+
+	return 0;
+}
+
+static int bd96801_set_wdt_mode(struct wdtbd96801 *w, unsigned int hw_margin,
+			       unsigned int hw_margin_min)
+{
+	int fastng, slowng, type, ret, reg, mask;
+	struct device *dev = w->dev;
+
+
+	if (hw_margin_min * 1000 > FASTNG_MAX_US) {
+		dev_err(dev, "Unsupported fast timeout %u uS [max %u]\n",
+			hw_margin_min * 1000, FASTNG_MAX_US);
+
+		return -EINVAL;
+	}
+
+	if (hw_margin * 1000 > SLOWNG_MAX_US) {
+		dev_err(dev, "Unsupported slow timeout %u uS [max %u]\n",
+			hw_margin * 1000, SLOWNG_MAX_US);
+
+		return -EINVAL;
+	}
+
+	/*
+	 * Convert to 100uS to guarantee reasonable timeouts fit in
+	 * 32bit maintaining also a decent accuracy.
+	 */
+	hw_margin *= 10;
+	hw_margin_min *= 10;
+
+	if (hw_margin_min) {
+		unsigned int min;
+
+		type = BD96801_WD_TYPE_WIN;
+		dev_dbg(dev, "Setting type WINDOW 0x%x\n", type);
+		ret = find_closest_fast(hw_margin_min, &fastng, &min);
+		if (ret)
+			return ret;
+
+		ret = find_closest_slow_by_fast(min, &hw_margin, &slowng);
+		if (ret) {
+			dev_err(dev,
+				"can't support slow timeout %u uS using fast %u uS. [max slow %u uS]\n",
+				hw_margin * 100, min * 100, min * 100 * 16);
+
+			return ret;
+		}
+		w->wdt.min_hw_heartbeat_ms = min / 10;
+	} else {
+		type = BD96801_WD_TYPE_SLOW;
+		dev_dbg(dev, "Setting type SLOW 0x%x\n", type);
+		ret = find_closest_slow(&hw_margin, &slowng, &fastng);
+		if (ret)
+			return ret;
+	}
+
+	w->wdt.max_hw_heartbeat_ms = hw_margin / 10;
+
+	fastng = FIELD_PREP(BD96801_WD_TMO_SHORT_MASK, fastng);
+
+	reg = slowng | fastng;
+	mask = BD96801_WD_RATIO_MASK | BD96801_WD_TMO_SHORT_MASK;
+	ret = regmap_update_bits(w->regmap, BD96801_REG_WD_TMO,
+				 mask, reg);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
+				 BD96801_WD_TYPE_MASK, type);
+
+	return ret;
+}
+
+static int bd96801_set_heartbeat_from_hw(struct wdtbd96801 *w,
+					 unsigned int conf_reg)
+{
+	int ret;
+	unsigned int val, sel, fast;
+
+	/*
+	 * The BD96801 supports a somewhat peculiar QA-mode, which we do not
+	 * support in this driver. If the QA-mode is enabled then we just
+	 * warn and bail-out.
+	 */
+	if ((conf_reg & BD96801_WD_EN_MASK) != BD96801_WD_IF_EN) {
+		dev_err(w->dev, "watchdog set to Q&A mode - exiting\n");
+		return -EINVAL;
+	}
+
+	ret = regmap_read(w->regmap, BD96801_REG_WD_TMO, &val);
+	if (ret)
+		return ret;
+
+	sel = FIELD_GET(BD96801_WD_TMO_SHORT_MASK, val);
+	fast = FASTNG_MIN << sel;
+
+	sel = (val & BD96801_WD_RATIO_MASK) + 1;
+	w->wdt.max_hw_heartbeat_ms = (fast << sel) / USEC_PER_MSEC;
+
+	if ((conf_reg & BD96801_WD_TYPE_MASK) == BD96801_WD_TYPE_WIN)
+		w->wdt.min_hw_heartbeat_ms = fast / USEC_PER_MSEC;
+
+	return 0;
+}
+
+static int init_wdg_hw(struct wdtbd96801 *w)
+{
+	u32 hw_margin[2];
+	int count, ret;
+	u32 hw_margin_max = BD96801_WDT_DEFAULT_MARGIN_MS, hw_margin_min = 0;
+
+	count = device_property_count_u32(w->dev->parent, "rohm,hw-timeout-ms");
+	if (count < 0 && count != -EINVAL)
+		return count;
+
+	if (count > 0) {
+		if (count > ARRAY_SIZE(hw_margin))
+			return -EINVAL;
+
+		ret = device_property_read_u32_array(w->dev->parent,
+						     "rohm,hw-timeout-ms",
+						     &hw_margin[0], count);
+		if (ret < 0)
+			return ret;
+
+		if (count == 1)
+			hw_margin_max = hw_margin[0];
+
+		if (count == 2) {
+			if (hw_margin[1] > hw_margin[0]) {
+				hw_margin_max = hw_margin[1];
+				hw_margin_min = hw_margin[0];
+			} else {
+				hw_margin_max = hw_margin[0];
+				hw_margin_min = hw_margin[1];
+			}
+		}
+	}
+
+	ret = bd96801_set_wdt_mode(w, hw_margin_max, hw_margin_min);
+	if (ret)
+		return ret;
+
+	ret = device_property_match_string(w->dev->parent, "rohm,wdg-action",
+					   "prstb");
+	if (ret >= 0) {
+		ret = regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
+				 BD96801_WD_ASSERT_MASK,
+				 BD96801_WD_ASSERT_RST);
+		return ret;
+	}
+
+	ret = device_property_match_string(w->dev->parent, "rohm,wdg-action",
+					   "intb-only");
+	if (ret >= 0) {
+		ret = regmap_update_bits(w->regmap, BD96801_REG_WD_CONF,
+				 BD96801_WD_ASSERT_MASK,
+				 BD96801_WD_ASSERT_IRQ);
+		return ret;
+	}
+
+	return 0;
+}
+
+static irqreturn_t bd96801_irq_hnd(int irq, void *data)
+{
+	emergency_restart();
+
+	return IRQ_NONE;
+}
+
+static int bd96801_wdt_probe(struct platform_device *pdev)
+{
+	struct wdtbd96801 *w;
+	int ret, irq;
+	unsigned int val;
+
+	w = devm_kzalloc(&pdev->dev, sizeof(*w), GFP_KERNEL);
+	if (!w)
+		return -ENOMEM;
+
+	w->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	w->dev = &pdev->dev;
+
+	w->wdt.info = &bd96801_wdt_info;
+	w->wdt.ops =  &bd96801_wdt_ops;
+	w->wdt.parent = pdev->dev.parent;
+	w->wdt.timeout = DEFAULT_TIMEOUT;
+	watchdog_set_drvdata(&w->wdt, w);
+
+	ret = regmap_read(w->regmap, BD96801_REG_WD_CONF, &val);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "Failed to get the watchdog state\n");
+
+	/*
+	 * If the WDG is already enabled we assume it is configured by boot.
+	 * In this case we just update the hw-timeout based on values set to
+	 * the timeout / mode registers and leave the hardware configs
+	 * untouched.
+	 */
+	if ((val & BD96801_WD_EN_MASK) != BD96801_WD_DISABLE) {
+		dev_dbg(&pdev->dev, "watchdog was running during probe\n");
+		ret = bd96801_set_heartbeat_from_hw(w, val);
+		if (ret)
+			return ret;
+
+		set_bit(WDOG_HW_RUNNING, &w->wdt.status);
+	} else {
+		/* If WDG is not running so we will initializate it */
+		ret = init_wdg_hw(w);
+		if (ret)
+			return ret;
+	}
+
+	dev_dbg(w->dev, "heartbeat set to %u - %u\n",
+		w->wdt.min_hw_heartbeat_ms, w->wdt.max_hw_heartbeat_ms);
+
+	watchdog_init_timeout(&w->wdt, 0, pdev->dev.parent);
+	watchdog_set_nowayout(&w->wdt, nowayout);
+	watchdog_stop_on_reboot(&w->wdt);
+
+	irq = platform_get_irq_byname(pdev, "bd96801-wdg");
+	if (irq > 0) {
+		ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+						bd96801_irq_hnd,
+						IRQF_ONESHOT,  "bd96801-wdg",
+						NULL);
+		if (ret)
+			return dev_err_probe(&pdev->dev, ret,
+					     "Failed to register IRQ\n");
+	}
+
+	return devm_watchdog_register_device(&pdev->dev, &w->wdt);
+}
+
+static const struct platform_device_id bd96801_wdt_id[] = {
+	{ "bd96801-wdt", },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, bd96801_wdt_id);
+
+static struct platform_driver bd96801_wdt = {
+	.driver = {
+		.name = "bd96801-wdt"
+	},
+	.probe = bd96801_wdt_probe,
+	.id_table = bd96801_wdt_id,
+};
+module_platform_driver(bd96801_wdt);
+
+MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>");
+MODULE_DESCRIPTION("BD96801 watchdog driver");
+MODULE_LICENSE("GPL");