A rather common kind of external watchdog circuit is one that is kept
alive by toggling a gpio. Add a driver for handling such a watchdog.
The compatible string is probably a little odd as it has nothing to do
with linux per se - however, I chose that to make .dts snippets
reusable between device trees used with U-Boot and linux, and this is
the (only) compatible string that linux' corresponding driver and DT
binding accepts. I have asked whether one should/could add "wdt-gpio"
to that binding, but the answer was no:
https://lore.kernel.org/lkml/CAL_JsqKEGaFpiFV_oAtE+S_bnHkg4qry+bhx2EDs=nsbvf_...@mail.gmail.com/
If someone feels strongly about this, I can certainly remove the
"linux," part from the string - it probably wouldn't the only place
where
one can't reuse a DT snippet as-is between linux and U-Boot.
Signed-off-by: Rasmus Villemoes <rasmus.villem...@prevas.dk>
---
.../watchdog/gpio-wdt.txt | 15 ++++++
drivers/watchdog/Kconfig | 7 +++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/gpio_wdt.c | 51
+++++++++++++++++++
4 files changed, 74 insertions(+)
create mode 100644 doc/device-tree-bindings/watchdog/gpio-wdt.txt
create mode 100644 drivers/watchdog/gpio_wdt.c
diff --git a/doc/device-tree-bindings/watchdog/gpio-wdt.txt
b/doc/device-tree-bindings/watchdog/gpio-wdt.txt
new file mode 100644
index 0000000000..2283b7ba6e
--- /dev/null
+++ b/doc/device-tree-bindings/watchdog/gpio-wdt.txt
@@ -0,0 +1,15 @@
+GPIO watchdog timer
+
+Describes a simple watchdog timer which is reset by toggling a gpio.
+
+Required properties:
+
+- compatible: must be "linux,wdt-gpio"
+- gpios: gpio to toggle when wdt driver reset method is called
+
+Example:
+
+ gpio-wdt {
+ gpios = <&gpio0 1 0>;
+ compatible = "linux,wdt-gpio";
+ };
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index f0ff2612a6..2cf378db29 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -147,6 +147,13 @@ config WDT_CORTINA
This driver support all CPU ISAs supported by Cortina
Access CAxxxx SoCs.
+config WDT_GPIO
+ bool "External gpio watchdog support"
+ depends on WDT
+ depends on DM_GPIO
+ help
+ Support for external watchdog fed by toggling a gpio.
+
config WDT_MPC8xx
bool "MPC8xx watchdog timer support"
depends on WDT && MPC8xx
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 5c7ef593fe..f14415bb8e 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_WDT_BOOKE) += booke_wdt.o
obj-$(CONFIG_WDT_CORTINA) += cortina_wdt.o
obj-$(CONFIG_WDT_ORION) += orion_wdt.o
obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o
+obj-$(CONFIG_WDT_GPIO) += gpio_wdt.o
obj-$(CONFIG_WDT_MPC8xx) += mpc8xx_wdt.o
obj-$(CONFIG_WDT_MT7620) += mt7620_wdt.o
obj-$(CONFIG_WDT_MT7621) += mt7621_wdt.o
diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c
new file mode 100644
index 0000000000..9dba9c254e
--- /dev/null
+++ b/drivers/watchdog/gpio_wdt.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <common.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <wdt.h>
+#include <asm/gpio.h>
+
+struct gpio_wdt_priv {
+ struct gpio_desc gpio;
+ int state;
+};
+
+static int gpio_wdt_reset(struct udevice *dev)
+{
+ struct gpio_wdt_priv *priv = dev_get_priv(dev);
+
+ priv->state = !priv->state;
+ return dm_gpio_set_value(&priv->gpio, priv->state);
+}
+
+static int dm_probe(struct udevice *dev)
+{
+ struct gpio_wdt_priv *priv = dev_get_priv(dev);
+ int ret;
+
+ ret = gpio_request_by_name(dev, "gpios", 0, &priv->gpio,
GPIOD_IS_OUT);
+ if (ret < 0) {
+ dev_err(dev, "Request for wdt gpio failed: %d\n", ret);
+ return ret;
+ }
+ return gpio_wdt_reset(dev);
+}
+
+static const struct wdt_ops gpio_wdt_ops = {
+ .reset = gpio_wdt_reset,
+};
