watchdog: qcom: introduce qcom-wdt driver

From: Caleb Connolly <caleb.connolly@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@linaro.org>
Signed-off-by: Paul Sajna <hello@paulsajna.com>
Tested-by: Paul Sajna <hello@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(+)


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

Best regards,

Hi,

On 13/04/2025 12:12, Paul Sajna wrote:
> From: Caleb Connolly <caleb.connolly@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@linaro.org>
> Signed-off-by: Paul Sajna <hello@paulsajna.com>
> Tested-by: Paul Sajna <hello@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@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);

Fine but perhaps just add a simple code into qcom_wdt_start() and add
a reset callback to allow people to actually use the wdog from u-boot
with CONFIG_WATCHDOG_AUTOSTART and/or u-boot,autostart.

No need to implement set_timeout, we can use the bootloader value.

> +
> +	return ret;
> +}
> +
> +static const struct wdt_ops qcom_wdt_ops = {
> +	.stop = qcom_wdt_stop,

You forgot qcom_wdt_start()

> +};
> +
> +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,