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_...@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, >> +}; > > 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. > 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). Rasmus