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Message-ID: <mfvuoslj27mbayypzr3wuagrq3p5wzelklgveedhwrxiaavwxy@7ipv2tup6oou>
Date: Wed, 3 Sep 2025 15:13:38 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: hrishabh.rajput@....qualcomm.com
Cc: Konrad Dybcio <konradybcio@...nel.org>,
Wim Van Sebroeck <wim@...ux-watchdog.org>, Guenter Roeck <linux@...ck-us.net>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org, linux-watchdog@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] watchdog: Add driver for Gunyah Watchdog
On Wed, Sep 03, 2025 at 07:34:00PM +0000, Hrishabh Rajput via B4 Relay wrote:
> From: Hrishabh Rajput <hrishabh.rajput@....qualcomm.com>
>
> Add driver to support the SMC-based watchdog timer provided by the
> Gunyah Hypervisor.
>
Start the commit message with a problem description, end with a
technical description of the solution. I.e. move this paragraph down.
> On Qualcomm SoCs running under the Gunyah hypervisor, access to watchdog
> through MMIO is not available. Depending on the hypervisor
> configuration, the watchdog is either fully emulated or exposed via
> ARM's SMC Calling Conventions (SMCCC) through the Vendor Specific
> Hypervisor Service Calls space.
>
> When the SMC-based interface is enabled, a device tree overlay is used
> to provide the pretimeout interrupt configuration.
>
> Signed-off-by: Hrishabh Rajput <hrishabh.rajput@....qualcomm.com>
[..]
> diff --git a/drivers/watchdog/gunyah_wdt.c b/drivers/watchdog/gunyah_wdt.c
[..]
> +#define GUNYAH_WDT_SMCCC_CALL_VAL(func_id) \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32,\
> + ARM_SMCCC_OWNER_VENDOR_HYP, func_id)
> +
> +/* SMCCC function IDs for watchdog operations */
> +#define GUNYAH_WDT_CONTROL GUNYAH_WDT_SMCCC_CALL_VAL(0x0005)
> +#define GUNYAH_WDT_STATUS GUNYAH_WDT_SMCCC_CALL_VAL(0x0006)
> +#define GUNYAH_WDT_PING GUNYAH_WDT_SMCCC_CALL_VAL(0x0007)
Uneven indentation.
> +#define GUNYAH_WDT_SET_TIME GUNYAH_WDT_SMCCC_CALL_VAL(0x0008)
> +
> +/*
> + * Control values for GUNYAH_WDT_CONTROL.
> + * Bit 0 is used to enable or disable the watchdog. If this bit is set,
> + * then the watchdog is enabled and vice versa.
> + * Bit 1 should always be set to 1 as this bit is reserved in Gunyah and
> + * it's expected to be 1.
> + */
> +#define WDT_CTRL_ENABLE (BIT(1) | BIT(0))
> +#define WDT_CTRL_DISABLE BIT(1)
> +
> +struct gunyah_wdt {
> + unsigned int pretimeout_irq;
This is only used momentarily in gunyah_wdt_probe(), make it a local
variable.
> + struct watchdog_device wdd;
Which means that gunyah_wdt is just watchdog_device, so you can drop
gunyah_wdt completely, and put wdd directly in drvdata.
> +};
> +
[..]
> +static int __init gunyah_wdt_init(void)
> +{
> + return platform_driver_register(&gunyah_wdt_driver);
> +}
> +
> +module_init(gunyah_wdt_init);
module_platform_driver(gunyah_wdt_driver);
> +
> +MODULE_DESCRIPTION("Gunyah Watchdog Driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/gunyah_errno.h b/include/linux/gunyah_errno.h
> new file mode 100644
> index 000000000000..518228e333bd
> --- /dev/null
> +++ b/include/linux/gunyah_errno.h
> @@ -0,0 +1,77 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
Isn't this content solely used from within gunyah_wdt.c? Why is it a
separate header file? Just move it into the c-file.
Regards,
Bjorn
> +
> +#ifndef _LINUX_GUNYAH_ERRNO_H
> +#define _LINUX_GUNYAH_ERRNO_H
> +
> +#include <linux/errno.h>
> +
> +enum gunyah_error {
> + GUNYAH_ERROR_OK = 0,
> + GUNYAH_ERROR_UNIMPLEMENTED = -1,
> + GUNYAH_ERROR_RETRY = -2,
> +
> + GUNYAH_ERROR_ARG_INVAL = 1,
> + GUNYAH_ERROR_ARG_SIZE = 2,
> + GUNYAH_ERROR_ARG_ALIGN = 3,
> +
> + GUNYAH_ERROR_NOMEM = 10,
> +
> + GUNYAH_ERROR_ADDR_OVFL = 20,
> + GUNYAH_ERROR_ADDR_UNFL = 21,
> + GUNYAH_ERROR_ADDR_INVAL = 22,
> +
> + GUNYAH_ERROR_DENIED = 30,
> + GUNYAH_ERROR_BUSY = 31,
> + GUNYAH_ERROR_IDLE = 32,
> +
> + GUNYAH_ERROR_IRQ_BOUND = 40,
> + GUNYAH_ERROR_IRQ_UNBOUND = 41,
> +
> + GUNYAH_ERROR_CSPACE_CAP_NULL = 50,
> + GUNYAH_ERROR_CSPACE_CAP_REVOKED = 51,
> + GUNYAH_ERROR_CSPACE_WRONG_OBJ_TYPE = 52,
> + GUNYAH_ERROR_CSPACE_INSUF_RIGHTS = 53,
> + GUNYAH_ERROR_CSPACE_FULL = 54,
> +
> + GUNYAH_ERROR_MSGQUEUE_EMPTY = 60,
> + GUNYAH_ERROR_MSGQUEUE_FULL = 61,
> +};
> +
> +/**
> + * gunyah_error_remap() - Remap Gunyah hypervisor errors into a Linux error code
> + * @gunyah_error: Gunyah hypercall return value
> + */
> +static inline int gunyah_error_remap(enum gunyah_error gunyah_error)
> +{
> + switch (gunyah_error) {
> + case GUNYAH_ERROR_OK:
> + return 0;
> + case GUNYAH_ERROR_NOMEM:
> + return -ENOMEM;
> + case GUNYAH_ERROR_DENIED:
> + case GUNYAH_ERROR_CSPACE_CAP_NULL:
> + case GUNYAH_ERROR_CSPACE_CAP_REVOKED:
> + case GUNYAH_ERROR_CSPACE_WRONG_OBJ_TYPE:
> + case GUNYAH_ERROR_CSPACE_INSUF_RIGHTS:
> + case GUNYAH_ERROR_CSPACE_FULL:
> + return -EACCES;
> + case GUNYAH_ERROR_BUSY:
> + case GUNYAH_ERROR_IDLE:
> + return -EBUSY;
> + case GUNYAH_ERROR_IRQ_BOUND:
> + case GUNYAH_ERROR_IRQ_UNBOUND:
> + case GUNYAH_ERROR_MSGQUEUE_FULL:
> + case GUNYAH_ERROR_MSGQUEUE_EMPTY:
> + return -EIO;
> + case GUNYAH_ERROR_UNIMPLEMENTED:
> + case GUNYAH_ERROR_RETRY:
> + return -EOPNOTSUPP;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +#endif
>
> --
> 2.43.0
>
>
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