watchdog: Add a driver for the Apple watchdog

This driver supports the watchdog timer found on Apple's M1 SoC.
On systems that use these SoC, the watchdog timer is the primary
way to reboot the system.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-on: Apple M1 Macbook
Tested-by: Simon Glass <sjg@chromium.org>

diff --git a/MAINTAINERS b/MAINTAINERS
index f4bd3d7..6ae81c5 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -116,6 +116,7 @@ F:  arch/arm/mach-apple/
 F:     configs/apple_m1_defconfig
 F:     drivers/iommu/apple_dart.c
 F:     drivers/pinctrl/pinctrl-apple.c
+F:     drivers/watchdog/apple_wdt.c
 F:     include/configs/apple.h
 
 ARM

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 1177f17..cabac29 100644 (file)
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -81,6 +81,15 @@ config WDT
          What exactly happens when the timer expires is up to a particular
          device/driver.
 
+config WDT_APPLE
+       bool "Apple watchdog timer support"
+       depends on WDT
+       default y if ARCH_APPLE
+       help
+         Enable support for the watchdog timer on Apple SoCs.
+         The watchdog will perform a full SoC reset resulting in a
+         reboot of the entire system.
+
 config WDT_ARMADA_37XX
        bool "Marvell Armada 37xx watchdog timer support"
        depends on WDT && ARMADA_3700

diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index fa7ce58..6d2b382 100644 (file)
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_DESIGNWARE_WATCHDOG) += designware_wdt.o
 obj-$(CONFIG_ULP_WATCHDOG) += ulp_wdog.o
 obj-$(CONFIG_$(SPL_TPL_)WDT) += wdt-uclass.o
 obj-$(CONFIG_WDT_SANDBOX) += sandbox_wdt.o
+obj-$(CONFIG_WDT_APPLE) += apple_wdt.o
 obj-$(CONFIG_WDT_ARMADA_37XX) += armada-37xx-wdt.o
 obj-$(CONFIG_WDT_ASPEED) += ast_wdt.o
 obj-$(CONFIG_WDT_AST2600) += ast2600_wdt.o

diff --git a/drivers/watchdog/apple_wdt.c b/drivers/watchdog/apple_wdt.c
new file mode 100644 (file)
index 0000000..c7307f4
--- /dev/null
+++ b/drivers/watchdog/apple_wdt.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Mark Kettenis <kettenis@openbsd.org>
+ */
+
+#include <clk.h>
+#include <dm.h>
+#include <wdt.h>
+#include <asm/io.h>
+#include <linux/delay.h>
+
+#define APPLE_WDT_CUR_TIME             0x10
+#define APPLE_WDT_BARK_TIME            0x14
+#define APPLE_WDT_CTRL                 0x1c
+#define  APPLE_WDT_CTRL_RESET_EN       BIT(2)
+
+struct apple_wdt_priv {
+       void *base;
+       ulong clk_rate;
+};
+
+static int apple_wdt_reset(struct udevice *dev)
+{
+       struct apple_wdt_priv *priv = dev_get_priv(dev);
+
+       writel(0, priv->base + APPLE_WDT_CUR_TIME);
+
+       return 0;
+}
+
+static int apple_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
+{
+       struct apple_wdt_priv *priv = dev_get_priv(dev);
+       u64 timeout;
+
+       timeout = (timeout_ms * priv->clk_rate) / 1000;
+       if (timeout > U32_MAX)
+               return -EINVAL;
+
+       writel(0, priv->base + APPLE_WDT_CUR_TIME);
+       writel(timeout, priv->base + APPLE_WDT_BARK_TIME);
+       writel(APPLE_WDT_CTRL_RESET_EN, priv->base + APPLE_WDT_CTRL);
+
+       return 0;
+}
+
+static int apple_wdt_stop(struct udevice *dev)
+{
+       struct apple_wdt_priv *priv = dev_get_priv(dev);
+
+       writel(0, priv->base + APPLE_WDT_CTRL);
+
+       return 0;
+}
+
+static int apple_wdt_expire_now(struct udevice *dev, ulong flags)
+{
+       int ret;
+
+       ret = apple_wdt_start(dev, 0, flags);
+       if (ret)
+               return ret;
+
+       /*
+        * It can take up to 25ms until the SoC actually resets, so
+        * wait 50ms just to be sure.
+        */
+       mdelay(50);
+
+       return 0;
+}
+
+static const struct wdt_ops apple_wdt_ops = {
+       .reset = apple_wdt_reset,
+       .start = apple_wdt_start,
+       .stop = apple_wdt_stop,
+       .expire_now = apple_wdt_expire_now,
+};
+
+static const struct udevice_id apple_wdt_ids[] = {
+       { .compatible = "apple,wdt" },
+       { /* sentinel */ }
+};
+
+static int apple_wdt_probe(struct udevice *dev)
+{
+       struct apple_wdt_priv *priv = dev_get_priv(dev);
+       struct clk clk;
+       int ret;
+
+       priv->base = dev_read_addr_ptr(dev);
+       if (!priv->base)
+               return -EINVAL;
+
+       ret = clk_get_by_index(dev, 0, &clk);
+       if (ret)
+               return ret;
+
+       ret = clk_enable(&clk);
+       if (ret)
+               return ret;
+
+       priv->clk_rate = clk_get_rate(&clk);
+
+       return 0;
+}
+
+U_BOOT_DRIVER(apple_wdt) = {
+       .name = "apple_wdt",
+       .id = UCLASS_WDT,
+       .of_match = apple_wdt_ids,
+       .priv_auto = sizeof(struct apple_wdt_priv),
+       .probe = apple_wdt_probe,
+       .ops = &apple_wdt_ops,
+};