[PATCH v3 2/2] watchdog: Add Apple SoC watchdog driver
Sven Peter
sven at svenpeter.dev
Sat Dec 11 04:36:33 PST 2021
Add support for the watchdog timer found in Apple SoCs. This driver is
also required to reboot these machines.
Tested-by: Janne Grunau <j at jannau.net>
Reviewed-by: Hector Martin <marcan at marcan.st>
Reviewed-by: Guenter Roeck <linux at roeck-us.net>
Signed-off-by: Sven Peter <sven at svenpeter.dev>
---
v2 -> v3:
- removed MAINTAINERS changes as requested by Hector Martin
to be able to take them through the soc tree instead
- typo fix: s/APPLE_WDTx_WD1_CUR_TIME/APPLE_WDT_WDx_CUR_TIME/
- added review and test tags
v1 -> v2:
- set the default timeout to 30s and call watchdog_init_timeout
to allow the device tree to override it
- set WDOG_HW_RUNNING if the watchdog is enabled at boot
- check that the clock rate is not zero
- use unsigned long instead of u32 for clk_rate
- use devm_add_action_or_reset instead of manually calling
clk_disable_unprepare
- explain the magic number in apple_wdt_restart
drivers/watchdog/Kconfig | 12 ++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/apple_wdt.c | 226 +++++++++++++++++++++++++++++++++++
3 files changed, 239 insertions(+)
create mode 100644 drivers/watchdog/apple_wdt.c
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 9d222ba17ec6..170dec880c8f 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -976,6 +976,18 @@ config MSC313E_WATCHDOG
To compile this driver as a module, choose M here: the
module will be called msc313e_wdt.
+config APPLE_WATCHDOG
+ tristate "Apple SoC watchdog"
+ depends on ARCH_APPLE || COMPILE_TEST
+ select WATCHDOG_CORE
+ help
+ Say Y here to include support for the Watchdog found in Apple
+ SoCs such as the M1. Next to the common watchdog features this
+ driver is also required in order to reboot these SoCs.
+
+ To compile this driver as a module, choose M here: the
+ module will be called apple_wdt.
+
# X86 (i386 + ia64 + x86_64) Architecture
config ACQUIRE_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2ee97064145b..270a518bd8f3 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -93,6 +93,7 @@ obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
obj-$(CONFIG_VISCONTI_WATCHDOG) += visconti_wdt.o
obj-$(CONFIG_MSC313E_WATCHDOG) += msc313e_wdt.o
+obj-$(CONFIG_APPLE_WATCHDOG) += apple_wdt.o
# X86 (i386 + ia64 + x86_64) Architecture
obj-$(CONFIG_ACQUIRE_WDT) += acquirewdt.o
diff --git a/drivers/watchdog/apple_wdt.c b/drivers/watchdog/apple_wdt.c
new file mode 100644
index 000000000000..16aca21f13d6
--- /dev/null
+++ b/drivers/watchdog/apple_wdt.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SoC Watchdog driver
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+/*
+ * Apple Watchdog MMIO registers
+ *
+ * This HW block has three separate watchdogs. WD0 resets the machine
+ * to recovery mode and is not very useful for us. WD1 and WD2 trigger a normal
+ * machine reset. WD0 additionally supports a configurable interrupt.
+ * This information can be used to implement pretimeout support at a later time.
+ *
+ * APPLE_WDT_WDx_CUR_TIME is a simple counter incremented for each tick of the
+ * reference clock. It can also be overwritten to any value.
+ * Whenever APPLE_WDT_CTRL_RESET_EN is set in APPLE_WDT_WDx_CTRL and
+ * APPLE_WDT_WDx_CUR_TIME >= APPLE_WDT_WDx_BITE_TIME the entire machine is
+ * reset.
+ * Whenever APPLE_WDT_CTRL_IRQ_EN is set and APPLE_WDTx_WD1_CUR_TIME >=
+ * APPLE_WDTx_WD1_BARK_TIME an interrupt is triggered and
+ * APPLE_WDT_CTRL_IRQ_STATUS is set. The interrupt can be cleared by writing
+ * 1 to APPLE_WDT_CTRL_IRQ_STATUS.
+ */
+#define APPLE_WDT_WD0_CUR_TIME 0x00
+#define APPLE_WDT_WD0_BITE_TIME 0x04
+#define APPLE_WDT_WD0_BARK_TIME 0x08
+#define APPLE_WDT_WD0_CTRL 0x0c
+
+#define APPLE_WDT_WD1_CUR_TIME 0x10
+#define APPLE_WDT_WD1_BITE_TIME 0x14
+#define APPLE_WDT_WD1_CTRL 0x1c
+
+#define APPLE_WDT_WD2_CUR_TIME 0x20
+#define APPLE_WDT_WD2_BITE_TIME 0x24
+#define APPLE_WDT_WD2_CTRL 0x2c
+
+#define APPLE_WDT_CTRL_IRQ_EN BIT(0)
+#define APPLE_WDT_CTRL_IRQ_STATUS BIT(1)
+#define APPLE_WDT_CTRL_RESET_EN BIT(2)
+
+#define APPLE_WDT_TIMEOUT_DEFAULT 30
+
+struct apple_wdt {
+ struct watchdog_device wdd;
+ void __iomem *regs;
+ unsigned long clk_rate;
+};
+
+static struct apple_wdt *to_apple_wdt(struct watchdog_device *wdd)
+{
+ return container_of(wdd, struct apple_wdt, wdd);
+}
+
+static int apple_wdt_start(struct watchdog_device *wdd)
+{
+ struct apple_wdt *wdt = to_apple_wdt(wdd);
+
+ writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
+ writel_relaxed(APPLE_WDT_CTRL_RESET_EN, wdt->regs + APPLE_WDT_WD1_CTRL);
+
+ return 0;
+}
+
+static int apple_wdt_stop(struct watchdog_device *wdd)
+{
+ struct apple_wdt *wdt = to_apple_wdt(wdd);
+
+ writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CTRL);
+
+ return 0;
+}
+
+static int apple_wdt_ping(struct watchdog_device *wdd)
+{
+ struct apple_wdt *wdt = to_apple_wdt(wdd);
+
+ writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
+
+ return 0;
+}
+
+static int apple_wdt_set_timeout(struct watchdog_device *wdd, unsigned int s)
+{
+ struct apple_wdt *wdt = to_apple_wdt(wdd);
+
+ writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
+ writel_relaxed(wdt->clk_rate * s, wdt->regs + APPLE_WDT_WD1_BITE_TIME);
+
+ wdd->timeout = s;
+
+ return 0;
+}
+
+static unsigned int apple_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+ struct apple_wdt *wdt = to_apple_wdt(wdd);
+ u32 cur_time, reset_time;
+
+ cur_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME);
+ reset_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_BITE_TIME);
+
+ return (reset_time - cur_time) / wdt->clk_rate;
+}
+
+static int apple_wdt_restart(struct watchdog_device *wdd, unsigned long mode,
+ void *cmd)
+{
+ struct apple_wdt *wdt = to_apple_wdt(wdd);
+
+ writel_relaxed(APPLE_WDT_CTRL_RESET_EN, wdt->regs + APPLE_WDT_WD1_CTRL);
+ writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_BITE_TIME);
+ writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
+
+ /*
+ * Flush writes and then wait for the SoC to reset. Even though the
+ * reset is queued almost immediately experiments have shown that it
+ * can take up to ~20-25ms until the SoC is actually reset. Just wait
+ * 50ms here to be safe.
+ */
+ (void)readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME);
+ mdelay(50);
+
+ return 0;
+}
+
+static void apple_wdt_clk_disable_unprepare(void *data)
+{
+ clk_disable_unprepare(data);
+}
+
+static struct watchdog_ops apple_wdt_ops = {
+ .owner = THIS_MODULE,
+ .start = apple_wdt_start,
+ .stop = apple_wdt_stop,
+ .ping = apple_wdt_ping,
+ .set_timeout = apple_wdt_set_timeout,
+ .get_timeleft = apple_wdt_get_timeleft,
+ .restart = apple_wdt_restart,
+};
+
+static struct watchdog_info apple_wdt_info = {
+ .identity = "Apple SoC Watchdog",
+ .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
+};
+
+static int apple_wdt_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct apple_wdt *wdt;
+ struct clk *clk;
+ u32 wdt_ctrl;
+ int ret;
+
+ wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
+ if (!wdt)
+ return -ENOMEM;
+
+ wdt->regs = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(wdt->regs))
+ return PTR_ERR(wdt->regs);
+
+ clk = devm_clk_get(dev, NULL);
+ if (IS_ERR(clk))
+ return PTR_ERR(clk);
+
+ ret = clk_prepare_enable(clk);
+ if (ret)
+ return ret;
+
+ ret = devm_add_action_or_reset(dev, apple_wdt_clk_disable_unprepare,
+ clk);
+ if (ret)
+ return ret;
+
+ wdt->clk_rate = clk_get_rate(clk);
+ if (!wdt->clk_rate)
+ return -EINVAL;
+
+ wdt->wdd.ops = &apple_wdt_ops;
+ wdt->wdd.info = &apple_wdt_info;
+ wdt->wdd.max_timeout = U32_MAX / wdt->clk_rate;
+ wdt->wdd.timeout = APPLE_WDT_TIMEOUT_DEFAULT;
+
+ wdt_ctrl = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CTRL);
+ if (wdt_ctrl & APPLE_WDT_CTRL_RESET_EN)
+ set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
+
+ watchdog_init_timeout(&wdt->wdd, 0, dev);
+ apple_wdt_set_timeout(&wdt->wdd, wdt->wdd.timeout);
+ watchdog_stop_on_unregister(&wdt->wdd);
+ watchdog_set_restart_priority(&wdt->wdd, 128);
+
+ return devm_watchdog_register_device(dev, &wdt->wdd);
+}
+
+static const struct of_device_id apple_wdt_of_match[] = {
+ { .compatible = "apple,wdt" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, apple_wdt_of_match);
+
+static struct platform_driver apple_wdt_driver = {
+ .driver = {
+ .name = "apple-watchdog",
+ .of_match_table = apple_wdt_of_match,
+ },
+ .probe = apple_wdt_probe,
+};
+module_platform_driver(apple_wdt_driver);
+
+MODULE_DESCRIPTION("Apple SoC watchdog driver");
+MODULE_AUTHOR("Sven Peter <sven at svenpeter.dev>");
+MODULE_LICENSE("Dual MIT/GPL");
--
2.25.1
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