On 11.05.21 08:40, Rasmus Villemoes wrote:
On 11/05/2021 07.55, Stefan Roese wrote:
On 10.05.21 17:47, Rasmus Villemoes wrote:
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...
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.villemoes@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, +};
I'm noticing that you don't have a "start" function. How is this GPIO watchdog enabled? Is it "always on"? Or does it start with the first triggering?
I have yet to encounter one of these that isn't always-running - it's more or less the only reason one would add an external watchdog circuit instead of relying on whatever the SOC has.
Okay.
Perhaps it makes sense to add a note about this into the driver to make this clear.
Will do. But I now see a much bigger problem due to some refactoring in wdt-uclass that basically requires a ->start method or GD_FLG_WDT_READY won't be set. Sigh.
I was actually hoping to get this small driver in first, then start doing the promised "handle _all_ registered watchdogs in wdt_uclass' watchdog_reset", because testing that is much easier once the sandbox test has two distinct "devices". I guess I'll just provide a dummy start method to work around that. Then when I equip wdt_uclass with some uclass-priv data that will contain not only the reset_period and last_reset metadata, but also keep track of whether the device is running (and then wdt_start() can be a no-op in that case, while the gpio driver can set that flag in its probe function).
Sounds very promising. Looking forward to your work on this.
Thanks, Stefan