drivers: watchdog: add mcf watchdog support

This watchdog driver applies to the following
mcf families:

- mcf52x2 (5271 5275 5282)
- mcf532x (5329 5373)
- mcf523x (5235)

Cpu's not listed for each family does not have WDT module.

Note, after some attempts testing by qemu on 5208 i
finally abandoned, watchdog seems not implemented properly.

The driver has been tested in a real M5282EVM.

Signed-off-by: Angelo Dureghello <angelo@kernel-space.org>
---
Changes for v2:
- remove unnecessary hardcoded timeouts
- remove unnecessary hw_watchdog_xxx stuff
- rewrite wdog module reg calculation
- using IS_ENABLED() where possible
Changes for v3:
- remove hardcoded 4s test

drivers/watchdog/Kconfig

@@ -178,6 +178,13 @@ config WDT_MAX6370
 	help
 	  Select this to enable max6370 watchdog timer.
 
+config WDT_MCF
+	bool "ColdFire family watchdog timer support"
+	depends on WDT
+	help
+	  Select this to enable ColdFire watchdog timer,
+	  which supports mcf52x2 mcf532x mcf523x families.
+
 config WDT_MESON_GXBB
 	bool "Amlogic watchdog timer support"
 	depends on WDT

drivers/watchdog/Makefile

@@ -31,6 +31,7 @@ obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o
 obj-$(CONFIG_WDT_FTWDT010) += ftwdt010_wdt.o
 obj-$(CONFIG_WDT_GPIO) += gpio_wdt.o
 obj-$(CONFIG_WDT_MAX6370) += max6370_wdt.o
+obj-$(CONFIG_WDT_MCF) += mcf_wdt.o
 obj-$(CONFIG_WDT_MESON_GXBB) += meson_gxbb_wdt.o
 obj-$(CONFIG_WDT_MPC8xxx) += mpc8xxx_wdt.o
 obj-$(CONFIG_WDT_MT7620) += mt7620_wdt.o

drivers/watchdog/mcf_wdt.c

@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * mcf_wdt.c - driver for ColdFire on-chip watchdog
+ *
+ * Author: Angelo Dureghello <angelo@kernel-space.org>
+ *
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <hang.h>
+#include <asm/io.h>
+#include <wdt.h>
+#include <linux/bitops.h>
+
+#define DIVIDER_5XXX	4096
+#define DIVIDER_5282	8192
+
+#define WCR_EN          BIT(0)
+#define WCR_HALTED      BIT(1)
+#define WCR_DOZE        BIT(2)
+#define WCR_WAIT        BIT(3)
+
+struct watchdog_regs {
+	u16 wcr;        /* Control */
+	u16 wmr;        /* Service */
+	u16 wcntr;      /* Counter */
+	u16 wsr;        /* Reset Status */
+};
+
+static void mcf_watchdog_reset(struct watchdog_regs *wdog)
+{
+	if (!IS_ENABLED(CONFIG_WATCHDOG_RESET_DISABLE)) {
+		writew(0x5555, &wdog->wsr);
+		writew(0xaaaa, &wdog->wsr);
+	}
+}
+
+static void mcf_watchdog_init(struct watchdog_regs *wdog, u32 fixed_divider,
+			      u64 timeout_msecs)
+{
+	u32 wdog_module, cycles_per_sec;
+
+	cycles_per_sec = CFG_SYS_CLK / fixed_divider;
+
+	wdog_module = cycles_per_sec * ((u32)timeout_msecs / 1000);
+	wdog_module += (cycles_per_sec / 1000) * ((u32)timeout_msecs % 1000);
+
+	/* Limit check, max 16 bits */
+	if (wdog_module > 0xffff)
+		wdog_module = 0xffff;
+
+	/* Set timeout and enable watchdog */
+	writew((u16)wdog_module, &wdog->wmr);
+	writew(WCR_EN, &wdog->wcr);
+
+	mcf_watchdog_reset(wdog);
+}
+
+struct mcf_wdt_priv {
+	void __iomem *base;
+	u32 fixed_divider;
+};
+
+static int mcf_wdt_expire_now(struct udevice *dev, ulong flags)
+{
+	hang();
+
+	return 0;
+}
+
+static int mcf_wdt_reset(struct udevice *dev)
+{
+	struct mcf_wdt_priv *priv = dev_get_priv(dev);
+
+	mcf_watchdog_reset(priv->base);
+
+	return 0;
+}
+
+static int mcf_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
+{
+	struct mcf_wdt_priv *priv = dev_get_priv(dev);
+
+	/* Timeout from fdt (timeout) comes in milliseconds */
+	mcf_watchdog_init(priv->base, priv->fixed_divider, timeout);
+
+	return 0;
+}
+
+static int mcf_wdt_stop(struct udevice *dev)
+{
+	struct mcf_wdt_priv *priv = dev_get_priv(dev);
+	struct watchdog_regs *wdog = (struct watchdog_regs *)priv->base;
+
+	setbits_be16(&wdog->wcr, WCR_HALTED);
+
+	return 0;
+}
+
+static int mcf_wdt_probe(struct udevice *dev)
+{
+	struct mcf_wdt_priv *priv = dev_get_priv(dev);
+
+	priv->base = dev_read_addr_ptr(dev);
+	if (!priv->base)
+		return -ENOENT;
+
+	priv->fixed_divider = (u32)dev_get_driver_data(dev);
+
+	return 0;
+}
+
+static const struct wdt_ops mcf_wdt_ops = {
+	.start		= mcf_wdt_start,
+	.stop		= mcf_wdt_stop,
+	.reset		= mcf_wdt_reset,
+	.expire_now	= mcf_wdt_expire_now,
+};
+
+static const struct udevice_id mcf_wdt_ids[] = {
+	{ .compatible = "fsl,mcf5208-wdt", .data = DIVIDER_5XXX },
+	{ .compatible = "fsl,mcf5282-wdt", .data = DIVIDER_5282 },
+	{}
+};
+
+U_BOOT_DRIVER(mcf_wdt) = {
+	.name		= "mcf_wdt",
+	.id		= UCLASS_WDT,
+	.of_match	= mcf_wdt_ids,
+	.probe		= mcf_wdt_probe,
+	.ops		= &mcf_wdt_ops,
+	.priv_auto	= sizeof(struct mcf_wdt_priv),
+	.flags		= DM_FLAG_PRE_RELOC,
+};