watchdog: MediaTek: add watchdog driver for MediaTek SoCs

This patch adds a common driver for the Mediatek SoC integrated
watchdog.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Tested-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/watchdog/Kconfig

@@ -103,6 +103,14 @@ config WDT_CDNS
 	   Select this to enable Cadence watchdog timer, which can be found on some
 	   Xilinx Microzed Platform.
 
+config WDT_MTK
+	bool "MediaTek watchdog timer support"
+	depends on WDT && ARCH_MEDIATEK
+	help
+	  Select this to enable watchdog timer for MediaTek SoCs.
+	  The watchdog timer is stopped when initialized.
+	  It performs full SoC reset.
+
 config XILINX_TB_WATCHDOG
 	bool "Xilinx Axi watchdog timer support"
 	depends on WDT

drivers/watchdog/Makefile

@@ -24,3 +24,4 @@ obj-$(CONFIG_WDT_ORION) += orion_wdt.o
 obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o
 obj-$(CONFIG_MPC8xx_WATCHDOG) += mpc8xx_wdt.o
 obj-$(CONFIG_WDT_MT7621) += mt7621_wdt.o
+obj-$(CONFIG_WDT_MTK) += mtk_wdt.o

drivers/watchdog/mtk_wdt.c

@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Watchdog driver for MediaTek SoCs
+ *
+ * Copyright (C) 2018 MediaTek Inc.
+ * Author: Ryder Lee <ryder.lee@mediatek.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <wdt.h>
+#include <asm/io.h>
+
+#define MTK_WDT_MODE			0x00
+#define MTK_WDT_LENGTH			0x04
+#define MTK_WDT_RESTART			0x08
+#define MTK_WDT_STATUS			0x0c
+#define MTK_WDT_INTERVAL		0x10
+#define MTK_WDT_SWRST			0x14
+#define MTK_WDT_REQ_MODE		0x30
+#define MTK_WDT_DEBUG_CTL		0x40
+
+#define WDT_MODE_KEY			(0x22 << 24)
+#define WDT_MODE_EN			BIT(0)
+#define WDT_MODE_EXTPOL			BIT(1)
+#define WDT_MODE_EXTEN			BIT(2)
+#define WDT_MODE_IRQ_EN			BIT(3)
+#define WDT_MODE_DUAL_EN		BIT(6)
+
+#define WDT_LENGTH_KEY			0x8
+#define WDT_LENGTH_TIMEOUT(n)		((n) << 5)
+
+#define WDT_RESTART_KEY			0x1971
+#define WDT_SWRST_KEY			0x1209
+
+struct mtk_wdt_priv {
+	void __iomem *base;
+};
+
+static int mtk_wdt_reset(struct udevice *dev)
+{
+	struct mtk_wdt_priv *priv = dev_get_priv(dev);
+
+	/* Reload watchdog duration */
+	writel(WDT_RESTART_KEY, priv->base + MTK_WDT_RESTART);
+
+	return 0;
+}
+
+static int mtk_wdt_stop(struct udevice *dev)
+{
+	struct mtk_wdt_priv *priv = dev_get_priv(dev);
+
+	clrsetbits_le32(priv->base + MTK_WDT_MODE, WDT_MODE_EN, WDT_MODE_KEY);
+
+	return 0;
+}
+
+static int mtk_wdt_expire_now(struct udevice *dev, ulong flags)
+{
+	struct mtk_wdt_priv *priv = dev_get_priv(dev);
+
+	/* Kick watchdog to prevent counter == 0 */
+	writel(WDT_RESTART_KEY, priv->base + MTK_WDT_RESTART);
+
+	/* Reset */
+	writel(WDT_SWRST_KEY, priv->base + MTK_WDT_SWRST);
+	hang();
+
+	return 0;
+}
+
+static void mtk_wdt_set_timeout(struct udevice *dev, unsigned int timeout)
+{
+	struct mtk_wdt_priv *priv = dev_get_priv(dev);
+
+	/*
+	 * One bit is the value of 512 ticks
+	 * The clock has 32 KHz
+	 */
+	timeout = WDT_LENGTH_TIMEOUT(timeout << 6) | WDT_LENGTH_KEY;
+	writel(timeout, priv->base + MTK_WDT_LENGTH);
+
+	mtk_wdt_reset(dev);
+}
+
+static int mtk_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
+{
+	struct mtk_wdt_priv *priv = dev_get_priv(dev);
+
+	mtk_wdt_set_timeout(dev, timeout);
+
+	/* Enable watchdog reset signal */
+	setbits_le32(priv->base + MTK_WDT_MODE,
+		     WDT_MODE_EN | WDT_MODE_KEY | WDT_MODE_EXTEN);
+
+	return 0;
+}
+
+static int mtk_wdt_probe(struct udevice *dev)
+{
+	struct mtk_wdt_priv *priv = dev_get_priv(dev);
+
+	priv->base = dev_read_addr_ptr(dev);
+	if (!priv->base)
+		return -ENOENT;
+
+	/* Clear status */
+	clrsetbits_le32(priv->base + MTK_WDT_MODE,
+			WDT_MODE_IRQ_EN | WDT_MODE_EXTPOL, WDT_MODE_KEY);
+
+	return mtk_wdt_stop(dev);
+}
+
+static const struct wdt_ops mtk_wdt_ops = {
+	.start = mtk_wdt_start,
+	.reset = mtk_wdt_reset,
+	.stop = mtk_wdt_stop,
+	.expire_now = mtk_wdt_expire_now,
+};
+
+static const struct udevice_id mtk_wdt_ids[] = {
+	{ .compatible = "mediatek,wdt"},
+	{}
+};
+
+U_BOOT_DRIVER(mtk_wdt) = {
+	.name = "mtk_wdt",
+	.id = UCLASS_WDT,
+	.of_match = mtk_wdt_ids,
+	.priv_auto_alloc_size = sizeof(struct mtk_wdt_priv),
+	.probe = mtk_wdt_probe,
+	.ops = &mtk_wdt_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};