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2ac8490412
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 <sjg@chromium.org> Reviewed-by: Stefan Roese <sr@denx.de> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
68 lines
1.3 KiB
C
68 lines
1.3 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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#include <dm.h>
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#include <dm/device_compat.h>
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#include <wdt.h>
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#include <asm/gpio.h>
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struct gpio_wdt_priv {
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struct gpio_desc gpio;
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bool always_running;
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int state;
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};
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static int gpio_wdt_reset(struct udevice *dev)
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{
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struct gpio_wdt_priv *priv = dev_get_priv(dev);
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priv->state = !priv->state;
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return dm_gpio_set_value(&priv->gpio, priv->state);
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}
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static int gpio_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
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{
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struct gpio_wdt_priv *priv = dev_get_priv(dev);
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if (priv->always_running)
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return 0;
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return -ENOSYS;
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}
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static int dm_probe(struct udevice *dev)
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{
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struct gpio_wdt_priv *priv = dev_get_priv(dev);
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int ret;
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priv->always_running = dev_read_bool(dev, "always-running");
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ret = gpio_request_by_name(dev, "gpios", 0, &priv->gpio, GPIOD_IS_OUT);
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if (ret < 0) {
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dev_err(dev, "Request for wdt gpio failed: %d\n", ret);
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return ret;
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}
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if (priv->always_running)
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ret = gpio_wdt_reset(dev);
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return ret;
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}
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static const struct wdt_ops gpio_wdt_ops = {
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.start = gpio_wdt_start,
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.reset = gpio_wdt_reset,
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};
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static const struct udevice_id gpio_wdt_ids[] = {
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{ .compatible = "linux,wdt-gpio" },
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{}
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};
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U_BOOT_DRIVER(wdt_gpio) = {
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.name = "wdt_gpio",
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.id = UCLASS_WDT,
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.of_match = gpio_wdt_ids,
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.ops = &gpio_wdt_ops,
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.probe = dm_probe,
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.priv_auto = sizeof(struct gpio_wdt_priv),
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};
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