[PATCH] watchdog: add amlogic watchdog support

[Philippe Boos]

Add support for hardware watchdog timer for Amlogic SoCs.
This driver has been heavily inspired by his Linux equivalent
(meson_gxbb_wdt.c).

Reviewed-by: Jerome Brunet <jbrunet at baylibre.com>
Signed-off-by: Philippe Boos <pboos at baylibre.com>

---

This watchdog driver has been tested on a GXL libretech-cc board and also on
a custom G12a board. I did the following test cases:
 * boot with a faulty boot command, then we reach watchdog reset successfully,
 * boot a Linux kernel with and without watchdog support, and check if it is
   working as expected.

 drivers/watchdog/Kconfig          |   6 ++
 drivers/watchdog/Makefile         |   1 +
 drivers/watchdog/meson_gxbb_wdt.c | 126 ++++++++++++++++++++++++++++++
 3 files changed, 133 insertions(+)
 create mode 100644 drivers/watchdog/meson_gxbb_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index c3eb8a8aec..81b60482c9 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -175,6 +175,12 @@ config WDT_MAX6370
 	help
 	  Select this to enable max6370 watchdog timer.
 
+config WDT_MESON_GXBB
+	bool "Amlogic watchdog timer support"
+	depends on WDT
+	help
+	  Amlogic watchdog timer support.
+
 config WDT_MPC8xx
 	bool "MPC8xx watchdog timer support"
 	depends on WDT && MPC8xx
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 1f6199beca..0e2f582a5f 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_WDT_ORION) += orion_wdt.o
 obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o
 obj-$(CONFIG_WDT_GPIO) += gpio_wdt.o
 obj-$(CONFIG_WDT_MAX6370) += max6370_wdt.o
+obj-$(CONFIG_WDT_MESON_GXBB) += meson_gxbb_wdt.o
 obj-$(CONFIG_WDT_MPC8xx) += mpc8xx_wdt.o
 obj-$(CONFIG_WDT_MT7620) += mt7620_wdt.o
 obj-$(CONFIG_WDT_MT7621) += mt7621_wdt.o
diff --git a/drivers/watchdog/meson_gxbb_wdt.c b/drivers/watchdog/meson_gxbb_wdt.c
new file mode 100644
index 0000000000..56b8a8990c
--- /dev/null
+++ b/drivers/watchdog/meson_gxbb_wdt.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2022 BayLibre, SAS.
+ */
+
+#include <clk.h>
+#include <common.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <reset.h>
+#include <wdt.h>
+#include <asm/io.h>
+#include <linux/bitops.h>
+
+#define GXBB_WDT_CTRL_REG			0x0
+#define GXBB_WDT_TCNT_REG			0x8
+#define GXBB_WDT_RSET_REG			0xc
+
+#define GXBB_WDT_CTRL_CLKDIV_EN			BIT(25)
+#define GXBB_WDT_CTRL_CLK_EN			BIT(24)
+#define GXBB_WDT_CTRL_EE_RESET			BIT(21)
+#define GXBB_WDT_CTRL_EN			BIT(18)
+
+#define GXBB_WDT_CTRL_DIV_MASK			GENMASK(17, 0)
+#define GXBB_WDT_TCNT_SETUP_MASK		GENMASK(15, 0)
+
+
+struct amlogic_wdt_priv {
+	void __iomem *reg_base;
+};
+
+static int amlogic_wdt_set_timeout(struct udevice *dev, u64 timeout_ms)
+{
+	struct amlogic_wdt_priv *data = dev_get_priv(dev);
+
+	if (timeout_ms > GXBB_WDT_TCNT_SETUP_MASK) {
+		dev_warn(dev, "%s: timeout_ms=%llu: maximum watchdog timeout "
+		         "exceeded\n", __func__, timeout_ms);
+		timeout_ms = GXBB_WDT_TCNT_SETUP_MASK;
+	}
+
+	writel(timeout_ms, data->reg_base + GXBB_WDT_TCNT_REG);
+
+	return 0;
+}
+
+static int amlogic_wdt_stop(struct udevice *dev)
+{
+	struct amlogic_wdt_priv *data = dev_get_priv(dev);
+
+	writel(readl(data->reg_base + GXBB_WDT_CTRL_REG) & ~GXBB_WDT_CTRL_EN,
+	       data->reg_base + GXBB_WDT_CTRL_REG);
+
+	return 0;
+}
+
+static int amlogic_wdt_start(struct udevice *dev, u64 time_ms, ulong flags)
+{
+	struct amlogic_wdt_priv *data = dev_get_priv(dev);
+
+	writel(readl(data->reg_base + GXBB_WDT_CTRL_REG) | GXBB_WDT_CTRL_EN,
+	       data->reg_base + GXBB_WDT_CTRL_REG);
+
+	return amlogic_wdt_set_timeout(dev, time_ms);
+}
+
+static int amlogic_wdt_reset(struct udevice *dev)
+{
+	struct amlogic_wdt_priv *data = dev_get_priv(dev);
+
+	writel(0, data->reg_base + GXBB_WDT_RSET_REG);
+
+	return 0;
+}
+
+static int amlogic_wdt_probe(struct udevice *dev)
+{
+	struct amlogic_wdt_priv *data = dev_get_priv(dev);
+	int ret;
+
+	data->reg_base = dev_remap_addr(dev);
+	if (!data->reg_base)
+		return -EINVAL;
+
+	struct clk clk;
+
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (ret)
+		return ret;
+
+	ret = clk_enable(&clk);
+	if (ret) {
+		clk_free(&clk);
+		return ret;
+	}
+
+	/* Setup with 1ms timebase */
+	writel(((clk_get_rate(&clk) / 1000) & GXBB_WDT_CTRL_DIV_MASK) |
+	       GXBB_WDT_CTRL_EE_RESET |
+	       GXBB_WDT_CTRL_CLK_EN |
+	       GXBB_WDT_CTRL_CLKDIV_EN,
+	       data->reg_base + GXBB_WDT_CTRL_REG);
+
+	return 0;
+}
+
+static const struct wdt_ops amlogic_wdt_ops = {
+	.start = amlogic_wdt_start,
+	.reset = amlogic_wdt_reset,
+	.stop = amlogic_wdt_stop,
+};
+
+static const struct udevice_id amlogic_wdt_ids[] = {
+	{ .compatible = "amlogic,meson-gxbb-wdt" },
+	{}
+};
+
+U_BOOT_DRIVER(amlogic_wdt) = {
+	.name = "amlogic_wdt",
+	.id = UCLASS_WDT,
+	.of_match = amlogic_wdt_ids,
+	.priv_auto = sizeof(struct amlogic_wdt_priv),
+	.probe = amlogic_wdt_probe,
+	.ops = &amlogic_wdt_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};
-- 
2.20.1