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Message-ID: <38df2f02-efc4-465b-aa64-4c9e2c1919d8@roeck-us.net>
Date: Tue, 20 May 2025 16:15:36 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Alexey Charkov <alchark@...il.com>, Krzysztof Kozlowski
<krzk@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski
<krzk+dt@...nel.org>, Wim Van Sebroeck <wim@...ux-watchdog.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, linux-watchdog@...r.kernel.org
Subject: Re: [PATCH v4 4/4] watchdog: Add support for VIA/WonderMedia SoC
watchdog functionality
On 5/20/25 13:01, Alexey Charkov wrote:
> 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@...il.com>
> ---
> MAINTAINERS | 1 +
> drivers/watchdog/Kconfig | 15 ++++++++
> drivers/watchdog/Makefile | 1 +
> drivers/watchdog/vt8500-wdt.c | 80 +++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 97 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 5362095240627f613638197fda275db6edc16cf7..97d1842625dbdf7fdca3556260662dab469ed091 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -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
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 0d8d37f712e8cfb4bf8156853baa13c23a57d6d9..8049ae630301a98123f97f6e3ee868bd3bf1534a 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -2003,6 +2003,21 @@ config PIC32_DMT
> To compile this driver as a loadable module, choose M here.
> The module will be called pic32-dmt.
>
> +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.
> +
> # PARISC Architecture
>
> # POWERPC Architecture
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index c9482904bf870a085c7fce2a439ac5089b6e6fee..3072786bf226c357102be3734fe6e701f753d45b 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -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
> diff --git a/drivers/watchdog/vt8500-wdt.c b/drivers/watchdog/vt8500-wdt.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..54fe5ad7695de36f6b3c1d28e955f00bef00e9db
> --- /dev/null
> +++ b/drivers/watchdog/vt8500-wdt.c
> @@ -0,0 +1,80 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (C) 2025 Alexey Charkov <alchark@...il.com */
> +
> +#include <linux/auxiliary_bus.h>
> +#include <linux/container_of.h>
> +#include <linux/io.h>
> +#include <linux/limits.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);
> + u64 deadline = info->timer_next(wdd->timeout * VT8500_TIMER_HZ);
> +
wdd->timeout is the soft timeout, which may be larger
than the maximum hardware timeout. That means you'll need
to use something like "min(wdd->timeout, U32_MAX / VT8500_TIMER_HZ)
* VT8500_TIMER_HZ" as parameter to the timer_next call.
> + writel((u32)deadline, info->wdt_match);
Can deadline overflow ?
> + writel(TIMER_WD_EN, 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@...il.com>");
> +MODULE_DESCRIPTION("Driver for the VIA VT8500 watchdog timer");
> +MODULE_LICENSE("GPL");
>
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