Date:   Thu, 02 Dec 2021 15:44:20 +0900
From:   "Hector Martin \"marcan\"" <marcan@...can.st>
To:     Sven Peter <sven@...npeter.dev>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>
CC:     Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, Janne Grunau <j@...nau.net>
Subject: Re: [PATCH v2 2/2] watchdog: Add Apple SoC watchdog driver



On 2021年12月1日 1:18:09 JST, Sven Peter <sven@...npeter.dev> wrote:
>Add support for the watchdog timer found in Apple SoCs. This driver is
>also required to reboot these machines.
>
>Signed-off-by: Sven Peter <sven@...npeter.dev>
>---
>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
>
> MAINTAINERS                  |   1 +
> drivers/watchdog/Kconfig     |  12 ++
> drivers/watchdog/Makefile    |   1 +
> drivers/watchdog/apple_wdt.c | 226 +++++++++++++++++++++++++++++++++++
> 4 files changed, 240 insertions(+)
> create mode 100644 drivers/watchdog/apple_wdt.c
>
>diff --git a/MAINTAINERS b/MAINTAINERS
>index 859201bbd4e8..6190f0b40983 100644
>--- a/MAINTAINERS
>+++ b/MAINTAINERS
>@@ -1757,6 +1757,7 @@ F:	drivers/i2c/busses/i2c-pasemi-platform.c
> F:	drivers/irqchip/irq-apple-aic.c
> F:	drivers/mailbox/apple-mailbox.c
> F:	drivers/pinctrl/pinctrl-apple-gpio.c
>+F:	drivers/watchdog/apple_wdt.c
> F:	include/dt-bindings/interrupt-controller/apple-aic.h
> F:	include/dt-bindings/pinctrl/apple.h
> F:	include/linux/apple-mailbox.h
>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..76e5bedd50d1
>--- /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_WDTx_WD1_CUR_TIME >= APPLE_WDTx_WD1_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@...npeter.dev>");
>+MODULE_LICENSE("Dual MIT/GPL");

Reviewed-by: Hector Martin <marcan@...can.st>

Thanks, looks good! Any chance you can do a quick v3 with the MAINTAINERS changes split off? As usual, I'd rather make life easier for people merging upstream :)

-- 
Hector Martin "marcan" (marcan@...can.st)
Public key: https://mrcn.st/pub

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