From 2ac8490412c98211750e5fde9b7a5cda3035d7fd Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Thu, 19 Aug 2021 11:57:04 +0200 Subject: watchdog: add gpio watchdog driver 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 corresponding linux driver apparently has support for some watchdog circuits which can be disabled by tri-stating the gpio, but I have never actually encountered such a chip in the wild; the whole point of adding an external watchdog is usually that it is not in any way under software control. For forward-compatibility, and to make DT describe the hardware, the current driver only supports devices that have the always-running property. I went a little back and forth on whether I should fail ->probe or only ->start, and ended up deciding ->start was the right place. 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_giA@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. Reviewed-by: Simon Glass Reviewed-by: Stefan Roese Signed-off-by: Rasmus Villemoes --- drivers/watchdog/gpio_wdt.c | 68 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 drivers/watchdog/gpio_wdt.c (limited to 'drivers/watchdog/gpio_wdt.c') diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c new file mode 100644 index 0000000000..982a66b3f9 --- /dev/null +++ b/drivers/watchdog/gpio_wdt.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0+ + +#include +#include +#include +#include + +struct gpio_wdt_priv { + struct gpio_desc gpio; + bool always_running; + 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 gpio_wdt_start(struct udevice *dev, u64 timeout, ulong flags) +{ + struct gpio_wdt_priv *priv = dev_get_priv(dev); + + if (priv->always_running) + return 0; + + return -ENOSYS; +} + +static int dm_probe(struct udevice *dev) +{ + struct gpio_wdt_priv *priv = dev_get_priv(dev); + int ret; + + priv->always_running = dev_read_bool(dev, "always-running"); + 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; + } + + if (priv->always_running) + ret = gpio_wdt_reset(dev); + + return ret; +} + +static const struct wdt_ops gpio_wdt_ops = { + .start = gpio_wdt_start, + .reset = gpio_wdt_reset, +}; + +static const struct udevice_id gpio_wdt_ids[] = { + { .compatible = "linux,wdt-gpio" }, + {} +}; + +U_BOOT_DRIVER(wdt_gpio) = { + .name = "wdt_gpio", + .id = UCLASS_WDT, + .of_match = gpio_wdt_ids, + .ops = &gpio_wdt_ops, + .probe = dm_probe, + .priv_auto = sizeof(struct gpio_wdt_priv), +}; -- cgit v1.2.3