[PATCH] watchdog: qcom: introduce qcom-wdt driver

[Paul Sajna]

From: Caleb Connolly <caleb.connolly at linaro.org>

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 disable the watchdog and prevent this
annoying behaviour.

Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
Signed-off-by: Paul Sajna <hello at paulsajna.com>
Tested-by: Paul Sajna <hello at paulsajna.com>
---
This patch introduces a simple watchdog driver for Qualcomm devices.

Some devices, including one I have been spending a lot of time with,
the LG G7 ThinQ (codename judyln, arch sdm845) will reset within 30
seconds if the watchdog is not serviced.

I have tested this patch from Caleb Connolly that is over a year old and has
not yet been upstreamed, and it is very useful to me. I can hardly use
u-boot on this device without it. I have received Caleb's permission to
work on upstreaming this patch.

This is my first contribution to U-Boot, and I am unfamiliar with
mailing list workflows, so please be patient :)
---
 configs/qcom_defconfig      |   2 +
 drivers/watchdog/Kconfig    |   7 ++++
 drivers/watchdog/Makefile   |   1 +
 drivers/watchdog/qcom-wdt.c | 100 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 110 insertions(+)

diff --git a/configs/qcom_defconfig b/configs/qcom_defconfig
index 537806450dc4a61d3c617cdd2b0cfb8eab1c343c..0232f6d51c552bd06c8ba72b71edb5cb72fe0706 100644
--- a/configs/qcom_defconfig
+++ b/configs/qcom_defconfig
@@ -144,3 +144,5 @@ CONFIG_VIDEO_FONT_16X32=y
 CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_NO_FB_CLEAR=y
 CONFIG_VIDEO_SIMPLE=y
+CONFIG_WDT_QCOM=y
+CONFIG_WDT=y
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 1bb67f5035231df9f6ce01adb08d074855393143..808f4e578e28e7812f93b393a7f7d95d9501cdd4 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -335,6 +335,13 @@ config WDT_K3_RTI_FW_FILE
 
 endif
 
+config WDT_QCOM
+	bool "Qualcomm watchdog timer support"
+	depends on WDT && ARCH_SNAPDRAGON
+	help
+	  Select this to enable Qualcomm watchdog timer, which can be found on
+	  some Qualcomm chips.
+
 config WDT_SANDBOX
 	bool "Enable Watchdog Timer support for Sandbox"
 	depends on SANDBOX && WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index e6bd4c587af6133c405dde6dbada8050debc781c..5eaabd4aba58c815de4165f901aecfba0e0da255 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -54,3 +54,4 @@ obj-$(CONFIG_WDT_SUNXI) += sunxi_wdt.o
 obj-$(CONFIG_WDT_TANGIER) += tangier_wdt.o
 obj-$(CONFIG_WDT_XILINX) += xilinx_wwdt.o
 obj-$(CONFIG_WDT_ADI) += adi_wdt.o
+obj-$(CONFIG_WDT_QCOM) += qcom-wdt.o
diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
new file mode 100644
index 0000000000000000000000000000000000000000..a7ce31ef811c717fd16700aa7d984a000763a93e
--- /dev/null
+++ b/drivers/watchdog/qcom-wdt.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ * Copyright (c) Linaro Ltd. 2024
+ *
+ * Authors:
+ *   Caleb Connolly <caleb.connolly at linaro.org>
+ *
+ * Derived from linux/drivers/watchdog/qcom-wdt.c
+ */
+
+#include <dm.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)
+{
+	/* unimplemented */
+	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))) {
+		printf("Failed to disable Qualcomm watchdog!\n");
+		return -EIO;
+	}
+
+	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);
+	int ret;
+
+	wdt->base = dev_read_addr_ptr(dev);
+	wdt->layout = data->offset;
+
+	ret = qcom_wdt_stop(dev);
+
+	return ret;
+}
+
+static const struct wdt_ops qcom_wdt_ops = {
+	.stop = qcom_wdt_stop,
+};
+
+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),
+};

---
base-commit: f3563fc30356c8079527b90e532407050dff7c7b
change-id: 20250413-b4-qcom-wdt-e7b913fc375e

Best regards,
-- 
Paul Sajna <hello at paulsajna.com>