watchdog: qcom: introduce qcom-wdt driver
Some Qualcomm device vendors decide to turn the watchdog on in the
bootloader, resulting in the device being reset if it isn't petted every
~30 seconds. Introduce a driver to keep the watchdog happy and prevent this
annoying behaviour.
Signed-off-by: Paul Sajna <hello@paulsajna.com>
Co-authored-by: Paul Sajna <hello@paulsajna.com>
Tested-by: Paul Sajna <hello@paulsajna.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Acked-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250422-b4-qcom-wdt-v3-1-730d4d5a858d@paulsajna.com
Signed-off-by: Casey Connolly <casey.connolly@linaro.org>
diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
new file mode 100644
index 0000000..3601ba9
--- /dev/null
+++ b/drivers/watchdog/qcom-wdt.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ * Copyright (c) Linaro Ltd. 2024
+ *
+ * Authors:
+ * Casey Connolly <casey.connolly@linaro.org>
+ * Paul Sajna <hello@paulsajna.com>
+ *
+ * Derived from linux/drivers/watchdog/qcom-wdt.c
+ */
+
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <wdt.h>
+
+#include <asm/io.h>
+
+enum wdt_reg {
+ WDT_RST,
+ WDT_EN,
+ WDT_STS,
+ WDT_BARK_TIME,
+ WDT_BITE_TIME,
+};
+
+struct qcom_wdt_match_data {
+ const u32 *offset;
+};
+
+struct qcom_wdt {
+ void __iomem *base;
+ const u32 *layout;
+};
+
+static const u32 reg_offset_data_kpss[] = {
+ [WDT_RST] = 0x4,
+ [WDT_EN] = 0x8,
+ [WDT_STS] = 0xC,
+ [WDT_BARK_TIME] = 0x10,
+ [WDT_BITE_TIME] = 0x14,
+};
+
+static const struct qcom_wdt_match_data match_data_kpss = {
+ .offset = reg_offset_data_kpss,
+};
+
+static void __iomem *wdt_addr(struct qcom_wdt *wdt, enum wdt_reg reg)
+{
+ return wdt->base + wdt->layout[reg];
+}
+
+int qcom_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
+{
+ struct qcom_wdt *wdt = dev_get_priv(dev);
+
+ writel(0, wdt_addr(wdt, WDT_EN));
+ writel(1, wdt_addr(wdt, WDT_RST));
+ writel(1, wdt_addr(wdt, WDT_EN));
+ if (readl(wdt_addr(wdt, WDT_EN)) != 1) {
+ dev_err(dev, "Failed to enable Qualcomm watchdog!\n");
+ return -EIO;
+ }
+ return 0;
+}
+
+int qcom_wdt_stop(struct udevice *dev)
+{
+ struct qcom_wdt *wdt = dev_get_priv(dev);
+
+ writel(0, wdt_addr(wdt, WDT_EN));
+ if (readl(wdt_addr(wdt, WDT_EN))) {
+ dev_err(dev, "Failed to disable Qualcomm watchdog!\n");
+ return -EIO;
+ }
+
+ return 0;
+}
+
+int qcom_wdt_reset(struct udevice *dev)
+{
+ struct qcom_wdt *wdt = dev_get_priv(dev);
+
+ writel(1, wdt_addr(wdt, WDT_RST));
+ return 0;
+}
+
+static int qcom_wdt_probe(struct udevice *dev)
+{
+ struct qcom_wdt *wdt = dev_get_priv(dev);
+ struct qcom_wdt_match_data *data = (void *)dev_get_driver_data(dev);
+
+ wdt->base = dev_read_addr_ptr(dev);
+ wdt->layout = data->offset;
+
+ return 0;
+}
+
+static const struct wdt_ops qcom_wdt_ops = {
+ .start = qcom_wdt_start,
+ .stop = qcom_wdt_stop,
+ .reset = qcom_wdt_reset,
+};
+
+static const struct udevice_id qcom_wdt_ids[] = {
+ { .compatible = "qcom,kpss-wdt", .data = (ulong)&match_data_kpss },
+ {}
+};
+
+U_BOOT_DRIVER(qcom_wdt) = {
+ .name = "qcom_wdt",
+ .id = UCLASS_WDT,
+ .of_match = qcom_wdt_ids,
+ .ops = &qcom_wdt_ops,
+ .probe = qcom_wdt_probe,
+ .priv_auto = sizeof(struct qcom_wdt),
+};