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Message-ID: <7276d39b-a514-4265-a125-7e08f364f979@oss.qualcomm.com>
Date: Thu, 4 Sep 2025 17:10:33 +0530
From: Hrishabh Rajput <hrishabh.rajput@....qualcomm.com>
To: Bjorn Andersson <andersson@...nel.org>
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 9/4/2025 1:43 AM, Bjorn Andersson wrote:
> 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.
Thanks, that would make more sense. Will rearrange this.
>> 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.
This crept in somehow. Will fix it. Thanks.
>> +#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.
That would definitely be a better way to do it. Thanks.
>> +};
>> +
> [..]
>> +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);
This is intentional. I intend to keep this module persistent. No
module_exit(gunyah_wdt_exit).
>> +
>> +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
This header file is partially taken from [1] and I have only renamed it
to gh_errno.h.
The error codes are not specific to watchdog and we have other drivers
in the patch series [2] (which [1] is a part of) that would be using this.
[1]
https://lore.kernel.org/all/20240222-gunyah-v17-3-1e9da6763d38@quicinc.com/
[2]
https://lore.kernel.org/all/20240222-gunyah-v17-0-1e9da6763d38@quicinc.com/
Thanks,
Hrishabh
>> +
>> +#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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