Watchdog: introduce ARM SBSA watchdog driver

According to Server Base System Architecture (SBSA) specification,
the SBSA Generic Watchdog has two stage timeouts: the first signal
(WS0) is for alerting the system by interrupt, the second one (WS1) is a
real hardware reset.
More details about the hardware specification of this device:
ARM DEN0029B - Server Base System Architecture (SBSA)

This driver can operate ARM SBSA Generic Watchdog as a single stage
In the single stage mode, when the timeout is reached, your system
will be reset by WS1. The first signal (WS0) is ignored.

Signed-off-by: Zhao Qiang <qiang.zhao@nxp.com>
Signed-off-by: Biwen Li <biwen.li@nxp.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

MAINTAINERS

@@ -689,6 +689,7 @@ M:	Priyanka Jain <priyanka.jain@nxp.com>
 S:	Maintained
 T:	git https://gitlab.denx.de/u-boot/custodians/u-boot-fsl-qoriq.git
 F:	drivers/watchdog/sp805_wdt.c
+F:	drivers/watchdog/sbsa_gwdt.c
 
 I2C
 M:	Heiko Schocher <hs@denx.de>

drivers/watchdog/Kconfig

@@ -163,6 +163,15 @@ config WDT_SANDBOX
 	  can be probed and supports all of the methods of WDT, but does not
 	  really do anything.
 
+config WDT_SBSA
+	bool "SBSA watchdog timer support"
+	depends on WDT
+	help
+	   Select this to enable SBSA watchdog timer.
+	   This driver can operate ARM SBSA Generic Watchdog as a single stage.
+	   In the single stage mode, when the timeout is reached, your system
+	   will be reset by WS1. The first signal (WS0) is ignored.
+
 config WDT_SP805
 	bool "SP805 watchdog timer support"
 	depends on WDT

drivers/watchdog/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_WDT_MPC8xx) += mpc8xx_wdt.o
 obj-$(CONFIG_WDT_MT7621) += mt7621_wdt.o
 obj-$(CONFIG_WDT_MTK) += mtk_wdt.o
 obj-$(CONFIG_WDT_OMAP3) += omap_wdt.o
+obj-$(CONFIG_WDT_SBSA) += sbsa_gwdt.o
 obj-$(CONFIG_WDT_SP805) += sp805_wdt.o
 obj-$(CONFIG_WDT_STM32MP) += stm32mp_wdt.o
 obj-$(CONFIG_WDT_TANGIER) += tangier_wdt.o

drivers/watchdog/sbsa_gwdt.c

@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Watchdog driver for SBSA
+ *
+ * Copyright 2020 NXP
+ */
+
+#include <asm/io.h>
+#include <common.h>
+#include <dm/device.h>
+#include <dm/fdtaddr.h>
+#include <dm/read.h>
+#include <linux/bitops.h>
+#include <linux/err.h>
+#include <watchdog.h>
+#include <wdt.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/* SBSA Generic Watchdog register definitions */
+/* refresh frame */
+#define SBSA_GWDT_WRR		0x000
+
+/* control frame */
+#define SBSA_GWDT_WCS		0x000
+#define SBSA_GWDT_WOR		0x008
+#define SBSA_GWDT_WCV		0x010
+
+/* refresh/control frame */
+#define SBSA_GWDT_W_IIDR	0xfcc
+#define SBSA_GWDT_IDR		0xfd0
+
+/* Watchdog Control and Status Register */
+#define SBSA_GWDT_WCS_EN	BIT(0)
+#define SBSA_GWDT_WCS_WS0	BIT(1)
+#define SBSA_GWDT_WCS_WS1	BIT(2)
+
+struct sbsa_gwdt_priv {
+	void __iomem *reg_refresh;
+	void __iomem *reg_control;
+};
+
+static int sbsa_gwdt_reset(struct udevice *dev)
+{
+	struct sbsa_gwdt_priv *priv = dev_get_priv(dev);
+
+	writel(0, priv->reg_refresh + SBSA_GWDT_WRR);
+
+	return 0;
+}
+
+static int sbsa_gwdt_start(struct udevice *dev, u64 timeout, ulong flags)
+{
+	struct sbsa_gwdt_priv *priv = dev_get_priv(dev);
+	u32 clk;
+
+	/*
+	 * it work in the single stage mode in u-boot,
+	 * The first signal (WS0) is ignored,
+	 * the timeout is (WOR * 2), so the WOR should be configured
+	 * to half value of timeout.
+	 */
+	clk = get_tbclk();
+	writel(clk / 2 * timeout,
+	       priv->reg_control + SBSA_GWDT_WOR);
+
+	/* writing WCS will cause an explicit watchdog refresh */
+	writel(SBSA_GWDT_WCS_EN, priv->reg_control + SBSA_GWDT_WCS);
+
+	return 0;
+}
+
+static int sbsa_gwdt_stop(struct udevice *dev)
+{
+	struct sbsa_gwdt_priv *priv = dev_get_priv(dev);
+
+	writel(0, priv->reg_control + SBSA_GWDT_WCS);
+
+	return 0;
+}
+
+static int sbsa_gwdt_expire_now(struct udevice *dev, ulong flags)
+{
+	sbsa_gwdt_start(dev, 0, flags);
+
+	return 0;
+}
+
+static int sbsa_gwdt_probe(struct udevice *dev)
+{
+	debug("%s: Probing wdt%u (sbsa-gwdt)\n", __func__, dev->seq);
+
+	return 0;
+}
+
+static int sbsa_gwdt_ofdata_to_platdata(struct udevice *dev)
+{
+	struct sbsa_gwdt_priv *priv = dev_get_priv(dev);
+
+	priv->reg_control = (void __iomem *)dev_read_addr_index(dev, 0);
+	if (IS_ERR(priv->reg_control))
+		return PTR_ERR(priv->reg_control);
+
+	priv->reg_refresh = (void __iomem *)dev_read_addr_index(dev, 1);
+	if (IS_ERR(priv->reg_refresh))
+		return PTR_ERR(priv->reg_refresh);
+
+	return 0;
+}
+
+static const struct wdt_ops sbsa_gwdt_ops = {
+	.start = sbsa_gwdt_start,
+	.reset = sbsa_gwdt_reset,
+	.stop = sbsa_gwdt_stop,
+	.expire_now = sbsa_gwdt_expire_now,
+};
+
+static const struct udevice_id sbsa_gwdt_ids[] = {
+	{ .compatible = "arm,sbsa-gwdt" },
+	{}
+};
+
+U_BOOT_DRIVER(sbsa_gwdt) = {
+	.name = "sbsa_gwdt",
+	.id = UCLASS_WDT,
+	.of_match = sbsa_gwdt_ids,
+	.probe = sbsa_gwdt_probe,
+	.priv_auto_alloc_size = sizeof(struct sbsa_gwdt_priv),
+	.ofdata_to_platdata = sbsa_gwdt_ofdata_to_platdata,
+	.ops = &sbsa_gwdt_ops,
+};