watchdog: introduce the ARM64 SBSA watchdog driver

The ARM Server Base System Architecture is a specification for ARM-based server systems. Among other things, it defines the behavior and register interface for a watchdog timer.

Signed-off-by Timur Tabi <[email protected]>

---

[v3]
removed cpu_to_le32
used __maybe_unused instead of #ifdef

  drivers/watchdog/Kconfig        |   9 ++
  drivers/watchdog/Makefile       |   1 +
  drivers/watchdog/arm_sbsa_wdt.c | 296 ++++++++++++++++++++++++++++++++++++++++
  3 files changed, 306 insertions(+)

create mode 100644 drivers/watchdog/arm_sbsa_wdt.c

drivers/watchdog/Kconfig +0 -0

index e5e7c55..b6e1cb4 100644

drivers/watchdog/Kconfig +6 -0

+	depends on ARM_ARCH_TIMER
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include watchdog timer support for ARM Server Base
+	  System Architecture (SBSA) systems.
+
  # AVR32 Architecture
 
  config AT32AP700X_WDT

drivers/watchdog/Makefile +1 -0

index 5c19294..063ab8c 100644
@@ -64,6 +64,7 @@ obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
  obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
  obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
  obj-$(CONFIG_MEDIATEK_WATCHDOG) += mtk_wdt.o
+obj-$(CONFIG_ARM_SBSA_WDT) += arm_sbsa_wdt.o
 
  # AVR32 Architecture
  obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o

drivers/watchdog/arm_sbsa_wdt.c new file +24 -0

new file mode 100644
index 0000000..0b35598
@@ -0,0 +1,296 @@
+/*
+ * Watchdog driver for SBSA-compliant watchdog timers
+ *
+ * Copyright (c) 2015, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * ARM Server Base System Architecture watchdog driver.
+ *
+ * Register descriptions are taken from the ARM Server Base System
+ * Architecture document (ARM-DEN-0029)
+ */
+
+#define pr_fmt(fmt) "sbsa-gwdt: " fmt
+
+#include <linux/module.h>
+#include <linux/watchdog.h>

drivers/watchdog/arm_sbsa_wdt.c new file +13 -0

+};
+
+/* Watchdog Refresh Frame */
+struct arm_sbsa_watchdog_refresh {
+	__le32 wrr;		/* Watchdog Refresh Register */
+	uint8_t res1[0xFCC - 0x004];
+	struct arm_sbsa_watchdog_ident ident;
+};
+
+/* Watchdog Control Frame */
+struct arm_sbsa_watchdog_control {
+	__le32 wcs;
+	__le32 res1;

drivers/watchdog/arm_sbsa_wdt.c new file +39 -0

+	return 0;
+}
+
+static int arm_sbsa_wdt_stop(struct watchdog_device *wdev)
+{
+	struct arm_sbsa_watchdog_data *data =
+		container_of(wdev, struct arm_sbsa_watchdog_data, wdev);
+
+	writel(0, &data->control->wcs);
+
+	return 0;
+}
+
+static int arm_sbsa_wdt_set_timeout(struct watchdog_device *wdev,
+	unsigned int timeout)
+{
+	struct arm_sbsa_watchdog_data *data =
+		container_of(wdev, struct arm_sbsa_watchdog_data, wdev);
+
+	wdev->timeout = timeout;
+	writel(arch_timer_get_cntfrq() * wdev->timeout, &data->control->wor);
+
+	return 0;
+}
+
+static int arm_sbsa_wdt_ping(struct watchdog_device *wdev)
+{
+	struct arm_sbsa_watchdog_data *data =
+		container_of(wdev, struct arm_sbsa_watchdog_data, wdev);
+
+	writel(1, &data->refresh->wrr);
+
+	return 0;
+}
+
+static unsigned int arm_sbsa_wdt_status(struct watchdog_device *wdev)
+{
+	struct arm_sbsa_watchdog_data *data =
+		container_of(wdev, struct arm_sbsa_watchdog_data, wdev);

drivers/watchdog/arm_sbsa_wdt.c new file +39 -0

+}
+
+static irqreturn_t arm_sbsa_wdt_interrupt(int irq, void *p)
+{
+	/*
+	 * The WS0 interrupt occurs after the first timeout, so we attempt
+	 * a manual reboot.  If this doesn't work, the WS1 timeout will
+	 * cause a hardware reset.
+	 */
+	pr_crit("Initiating system reboot\n");
+	emergency_restart();
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * Disable watchdog if it is active during suspend
+ */
+static int __maybe_unused arm_sbsa_wdt_suspend(struct device *dev)
+{
+	struct arm_sbsa_watchdog_data *data = dev_get_drvdata(dev);
+
+	data->pm_status = readl(&data->control->wcs) & 1;
+
+	if (data->pm_status)
+		writel(0, &data->control->wcs);
+
+	return 0;
+}
+
+/*
+ * Enable watchdog and configure it if necessary
+ */
+static int __maybe_unused arm_sbsa_wdt_resume(struct device *dev)
+{
+	struct arm_sbsa_watchdog_data *data = dev_get_drvdata(dev);
+
+	if (data->pm_status)
+		writel(1, &data->control->wcs);

drivers/watchdog/arm_sbsa_wdt.c new file +29 -0

+	.identity = "ARM SBSA watchdog",
+};
+
+static struct watchdog_ops arm_sbsa_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = arm_sbsa_wdt_start,
+	.stop = arm_sbsa_wdt_stop,
+	.ping = arm_sbsa_wdt_ping,
+	.set_timeout = arm_sbsa_wdt_set_timeout,
+	.status = arm_sbsa_wdt_status,
+	.get_timeleft = arm_sbsa_wdt_timeleft,
+};
+
+static int __init arm_sbsa_wdt_probe(struct platform_device *pdev)
+{
+	struct arm_sbsa_watchdog_data *data;
+	struct resource *res;
+	uint32_t iidr;
+	int irq, ret;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "control");
+	data->control = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(data->control))
+		return PTR_ERR(data->control);
+

drivers/watchdog/arm_sbsa_wdt.c new file +17 -0

+		return -ENODEV;
+	}
+
+	irq = platform_get_irq_byname(pdev, "ws0");
+	if (irq < 0) {
+		dev_err(&pdev->dev, "could not get interrupt\n");
+		return irq;
+	}
+
+	ret = devm_request_irq(&pdev->dev, irq, arm_sbsa_wdt_interrupt,
+			       0, pdev->name, NULL);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "could not request irq %i (ret=%i)\n",
+			irq, ret);
+		return ret;
+	}
+

drivers/watchdog/arm_sbsa_wdt.c new file +55 -0

+	/*
+	 * Bits [15:12] are an implementation-defined revision number
+	 * for the component.
+	 */
+	arm_sbsa_wdt_info.firmware_version = (iidr >> 12) & 0xf;
+
+	ret = watchdog_register_device(&data->wdev);
+	if (ret < 0) {
+		dev_err(&pdev->dev,
+			"could not register watchdog device (ret=%i)\n", ret);
+		return ret;
+	}
+
+	dev_dbg(&pdev->dev, "implementer code is %03x\n",
+		 (iidr & 0xf00) >> 1 | (iidr & 0x7f));
+	dev_info(&pdev->dev, "maximum timeout is %u seconds\n",
+		 data->wdev.max_timeout);
+
+	platform_set_drvdata(pdev, data);
+
+	return 0;
+}
+
+static int __exit arm_sbsa_wdt_remove(struct platform_device *pdev)
+{
+	struct arm_sbsa_watchdog_data *data = platform_get_drvdata(pdev);
+
+	watchdog_unregister_device(&data->wdev);
+
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_OF)
+static const struct of_device_id arm_sbsa_wdt_of_match[] = {
+	{ .compatible = "arm,sbsa-gwdt" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, arm_sbsa_wdt_of_match);
+#endif
+
+static struct platform_driver arm_sbsa_wdt_driver = {
+	.driver = {
+		.name = "sbsa-gwdt",
+		.owner = THIS_MODULE,
+		.pm = &arm_sbsa_wdt_pm_ops,
+		.of_match_table = of_match_ptr(arm_sbsa_wdt_of_match),
+	},
+	.probe = arm_sbsa_wdt_probe,
+	.remove = __exit_p(arm_sbsa_wdt_remove),
+};
+
+module_platform_driver(arm_sbsa_wdt_driver);
+
+MODULE_DESCRIPTION("ARM Server Base System Architecture Watchdog Driver");
+MODULE_LICENSE("GPL v2");

drivers/watchdog/Kconfig config MEDIATEK_WATCHDOG · line 519

Quoted 3 lines

drivers/watchdog/Kconfig +3 -0

+config ARM_SBSA_WDT
+    tristate "ARM Server Base System Architecture watchdog"
+    depends on ARM64 || COMPILE_TEST

COMPILE_TEST doesn't work with the current code - see below.

I still don't understand why you can not use the standard arch_sys_counter provided for arm but have to call arm-internal functions directly. That seems quite broken to me.

drivers/watchdog/arm_sbsa_wdt.c line 41

Quoted 7 lines

drivers/watchdog/arm_sbsa_wdt.c new file +7 -0

+#include <linux/acpi.h>
+
+/* Watchdog Interface Identification Registers */
+struct arm_sbsa_watchdog_ident {
+    __le32 w_iidr;    /* Watchdog Interface Identification Register */
+    uint8_t res2[0xFE8 - 0xFD0];
+    __le32 w_pidr2;    /* Peripheral ID2 Register */

Does this register have any use ?

drivers/watchdog/arm_sbsa_wdt.c line 64

Quoted 3 lines

drivers/watchdog/arm_sbsa_wdt.c new file +3 -0

+struct arm_sbsa_watchdog_data {
+    struct watchdog_device wdev;
+    unsigned int pm_status;

You can use bool here.

drivers/watchdog/arm_sbsa_wdt.c line 76

Quoted 8 lines

drivers/watchdog/arm_sbsa_wdt.c new file +8 -0

+static int arm_sbsa_wdt_start(struct watchdog_device *wdev)
+{
+    struct arm_sbsa_watchdog_data *data =
+        container_of(wdev, struct arm_sbsa_watchdog_data, wdev);
+
+    /* Writing to the control register will also reset the counter */
+    writel(1, &data->control->wcs);
+

Is it ok to always overwrite the entire wcs register ?

Quoted 7 lines

drivers/watchdog/arm_sbsa_wdt.c new file +5 -0

+static unsigned int arm_sbsa_wdt_timeleft(struct watchdog_device *wdev)
+{
+    struct arm_sbsa_watchdog_data *data =
+        container_of(wdev, struct arm_sbsa_watchdog_data, wdev);
+    uint64_t diff = readq(&data->control->wcv) -

arch_counter_get_cntvct();
+

Due to this readq the code doesn't compile on arm, nor on any other architecture which does not implement readq.

Quoted 1 line

+ return diff / arch_timer_get_cntfrq();

.. and as mentioned before this won't compile on 32 bit targets.

Review

Quoted 2 lines

(quoted diff) +2 -0

+static struct watchdog_info arm_sbsa_wdt_info = {
+    .options = WDIOF_SETTIMEOUT | _WDIOF_KEEPALIVEPING,

WDIOF_MAGICCLOSE ?

drivers/watchdog/arm_sbsa_wdt.c line 214

Quoted 5 lines

drivers/watchdog/arm_sbsa_wdt.c new file +5 -0

+    /* We only support architecture version 0 */
+    iidr = readl(&data->control->ident.w_iidr);
+    if (((iidr >> 16) & 0xf) != 0) {
+        dev_info(&pdev->dev,
+             "only architecture version 0 is supported\n");

dev_err ?
It might make sense to display the detected version as well.

drivers/watchdog/arm_sbsa_wdt.c line 241

Quoted 2 lines

drivers/watchdog/arm_sbsa_wdt.c new file +2 -0

+    watchdog_set_drvdata(&data->wdev, data);
+

You don't ever call watchdog_get_drvdata(), so this is unnecessary.