@@ -3447,6 +3447,7 @@ F: drivers/tty/serial/vt8500_serial.c
F: drivers/video/fbdev/vt8500lcdfb.*
F: drivers/video/fbdev/wm8505fb*
F: drivers/video/fbdev/wmt_ge_rops.*
+F: drivers/watchdog/vt8500-wdt.c
F: include/linux/vt8500-timer.h
ARM/ZYNQ ARCHITECTURE
@@ -1115,6 +1115,21 @@ config SUNPLUS_WATCHDOG
To compile this driver as a module, choose M here: the
module will be called sunplus_wdt.
+config VT8500_WATCHDOG
+ tristate "VIA/WonderMedia VT8500 watchdog support"
+ depends on ARCH_VT8500 || COMPILE_TEST
+ select WATCHDOG_CORE
+ select AUXILIARY_BUS
+ help
+ VIA/WonderMedia SoCs can use their system timer as a hardware
+ watchdog, as long as the first timer channel is free from other
+ uses and respective function is enabled in its registers. To
+ make use of it, say Y here and ensure that the device tree
+ lists at least two interrupts for the VT8500 timer device.
+
+ To compile this driver as a module, choose M here.
+ The module will be called vt8500-wdt.
+
# X86 (i386 + ia64 + x86_64) Architecture
config ACQUIRE_WDT
@@ -101,6 +101,7 @@ obj-$(CONFIG_MSC313E_WATCHDOG) += msc313e_wdt.o
obj-$(CONFIG_APPLE_WATCHDOG) += apple_wdt.o
obj-$(CONFIG_SUNPLUS_WATCHDOG) += sunplus_wdt.o
obj-$(CONFIG_MARVELL_GTI_WDT) += marvell_gti_wdt.o
+obj-$(CONFIG_VT8500_WATCHDOG) += vt8500-wdt.o
# X86 (i386 + ia64 + x86_64) Architecture
obj-$(CONFIG_ACQUIRE_WDT) += acquirewdt.o
new file mode 100644
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2025 Alexey Charkov <alchark@gmail.com */
+
+#include <linux/auxiliary_bus.h>
+#include <linux/container_of.h>
+#include <linux/io.h>
+#include <linux/limits.h>
+#include <linux/minmax.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+#include <linux/vt8500-timer.h>
+
+static int vt8500_watchdog_start(struct watchdog_device *wdd)
+{
+ struct vt8500_wdt_info *info = watchdog_get_drvdata(wdd);
+ u32 deadline = min(wdd->timeout * 1000, wdd->max_hw_heartbeat_ms);
+
+ /* The deadline is matched against the hardware clocksource counter,
+ * which is a u32 value incrementing at VT8500_TIMER_HZ and continuing
+ * past wraparound. When the return value of timer_next is greater than
+ * U32_MAX then the match should occur after the hardware counter wraps
+ * around, thus we take only the lower 32 bits of timer_next return val
+ */
+ deadline = info->timer_next((u64)deadline * (VT8500_TIMER_HZ / 1000));
+ writel(deadline, info->wdt_match);
+ writel(1, info->wdt_en);
+ return 0;
+}
+
+static int vt8500_watchdog_stop(struct watchdog_device *wdd)
+{
+ struct vt8500_wdt_info *info = watchdog_get_drvdata(wdd);
+
+ writel(0, info->wdt_en);
+ return 0;
+}
+
+static const struct watchdog_ops vt8500_watchdog_ops = {
+ .start = vt8500_watchdog_start,
+ .stop = vt8500_watchdog_stop,
+};
+
+static const struct watchdog_info vt8500_watchdog_info = {
+ .identity = "VIA VT8500 watchdog",
+ .options = WDIOF_MAGICCLOSE |
+ WDIOF_KEEPALIVEPING |
+ WDIOF_SETTIMEOUT,
+};
+
+static int vt8500_wdt_probe(struct auxiliary_device *auxdev,
+ const struct auxiliary_device_id *id)
+{
+ struct vt8500_wdt_info *info;
+ struct watchdog_device *wdd;
+
+ wdd = devm_kzalloc(&auxdev->dev, sizeof(*wdd), GFP_KERNEL);
+ if (!wdd)
+ return -ENOMEM;
+
+ wdd->info = &vt8500_watchdog_info;
+ wdd->ops = &vt8500_watchdog_ops;
+ wdd->max_hw_heartbeat_ms = U32_MAX / (VT8500_TIMER_HZ / 1000);
+ wdd->parent = &auxdev->dev;
+
+ info = container_of(auxdev, struct vt8500_wdt_info, auxdev);
+ watchdog_set_drvdata(wdd, info);
+
+ return devm_watchdog_register_device(&auxdev->dev, wdd);
+}
+
+static const struct auxiliary_device_id vt8500_wdt_ids[] = {
+ { .name = "timer_vt8500.vt8500-wdt" },
+ {},
+};
+
+MODULE_DEVICE_TABLE(auxiliary, my_auxiliary_id_table);
+
+static struct auxiliary_driver vt8500_wdt_driver = {
+ .name = "vt8500-wdt",
+ .probe = vt8500_wdt_probe,
+ .id_table = vt8500_wdt_ids,
+};
+module_auxiliary_driver(vt8500_wdt_driver);
+
+MODULE_AUTHOR("Alexey Charkov <alchark@gmail.com>");
+MODULE_DESCRIPTION("Driver for the VIA VT8500 watchdog timer");
+MODULE_LICENSE("GPL");
VIA/WonderMedia SoCs can use their system timer's first channel as a watchdog device which will reset the system if the clocksource counter matches the value given in its match register 0 and if the watchdog function is enabled. Since the watchdog function is tightly coupled to the timer itself, it is implemented as an auxiliary device of the timer device Signed-off-by: Alexey Charkov <alchark@gmail.com> --- MAINTAINERS | 1 + drivers/watchdog/Kconfig | 15 ++++++++ drivers/watchdog/Makefile | 1 + drivers/watchdog/vt8500-wdt.c | 88 +++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 105 insertions(+)