linux-kernel - Re: [PATCH v7 0/2] Add support for Gunyah Watchdog

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Message-ID: <168374f9-cf03-481b-b4b2-ed51787a3def@linaro.org>
Date: Mon, 17 Nov 2025 15:45:31 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: hrishabh.rajput@....qualcomm.com, Bjorn Andersson <andersson@...nel.org>,
 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>
Cc: linux-arm-msm@...r.kernel.org, linux-watchdog@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Pavan Kondeti <pavan.kondeti@....qualcomm.com>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Subject: Re: [PATCH v7 0/2] Add support for Gunyah Watchdog

On 11/14/25 08:57, Hrishabh Rajput via B4 Relay wrote:
> Gunyah is a Type-I hypervisor which was introduced in the patch series
> [1]. It is an open source hypervisor. The source repo is available at
> [2].
> 
> The Gunyah Hypervisor doesn't allow its Virtual Machines to directly
> access the MMIO watchdog. It either provides the fully emulated MMIO
> based watchdog interface or the SMC-based watchdog interface depending
> on the hypervisor configuration.
> The SMC-based watchdog follows ARM's SMC Calling Convention (SMCCC)
> version 1.1 and uses Vendor Specific Hypervisor Service Calls space.
> 
> This patch series adds support for the SMC-based watchdog interface
> provided by the Gunyah Hypervisor.
> 
> This series is tested on SM8750 platform.
> 
> [1]
> https://lore.kernel.org/all/20240222-gunyah-v17-0-1e9da6763d38@quicinc.com/
> 
> [2]
> https://github.com/quic/gunyah-hypervisor
> 
> Signed-off-by: Hrishabh Rajput <hrishabh.rajput@....qualcomm.com>
> ---
> Changes in v7:
> - Convert local `const` arrays to `static const` to optimize
>    initialization and stack allocation.
> - Link to v6: https://lore.kernel.org/r/20251112-gunyah_watchdog-v6-0-38ad01f8dac0@oss.qualcomm.com
> 
> Changes in v6:
> - Fix build issues reported by the kernel test robot on PowerPC and RISC-V
>    architectures by adding IS_ENABLED(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) check
>    before calling arm_smccc_hypervisor_has_uuid().
> - Link to v5: https://lore.kernel.org/r/20251107-gunyah_watchdog-v5-0-4c6e3fb6eb17@oss.qualcomm.com
> 
> Changes in v5:
> - Move the gunyah_wdt device registration from the SMEM driver to the
>    SCM driver. Add additional logic to check if we're running under the
>    Gunyah Hypervisor.
> - Implement .remove() for gunyah_wdt driver to make it not persistent.
> - Link to v4: https://lore.kernel.org/r/20251031-gunyah_watchdog-v4-0-7abb1ee11315@oss.qualcomm.com
> 
> Changes in v4:
> - Move the contents of gunyah_wdt_init() to qcom_smem_probe() to make
>    sure we're registering the watchdog only on the Qualcomm devices.
> - Link to v3: https://lore.kernel.org/r/20251028-gunyah_watchdog-v3-1-e6d1ea438b1d@oss.qualcomm.com
> 
> Changes in v3:
> - Move back to platform driver model. In module init, determine if we're
>    running on a Qualcomm device and there is no supported memory-mapped
>    watchdog present. Then proceed to register platform device and driver
>    for SMC-based Gunyah watchdog.
> - To determine if we're running on a Qualcomm device we're checking the
>    presence of "qcom,smem" compatible devicetree node. As an alternative,
>    we also tried using socinfo for the same purpose. When both
>    gunyah_wdt and socinfo drivers were made built-in, it couldn't be
>    ensured that the socinfo driver probed successfully before gunyah_wdt
>    init was called. Hence, we resorted to the devicetree node approach.
> - Limit the errors listed in gunyah_error to the ones that can be
>    produced by the driver.
> - Link to v2: https://lore.kernel.org/r/20251006-gunyah_watchdog-v2-1-b99d41d45450@oss.qualcomm.com
> 
> Changes in v2:
> - Move away from platform driver model since the devicetree overlay does
>    not happen by default.
>    See https://lore.kernel.org/all/91002189-9d9e-48a2-8424-c42705fed3f8@quicinc.com/
> - Only when MMIO-based watchdog device is absent in the devicetree,
>    proceed to detect SMC-based watchdog using GUNYAH_WDT_STATUS SMC and
>    initialize if SMC returns success.
> - Implement pm notifiers as gunyah_wdt is no longer a platform driver so
>    dev_pm_ops cannot be used.
> - Pretimeout IRQ is no longer supported.
> - Remove struct gunyah_wdt since it is not required.
> - Move the contents of gunyah_errno.h to gunyah_wdt.c.
> - Link to v1: https://lore.kernel.org/r/20250903-gunyah_watchdog-v1-0-3ae690530e4b@oss.qualcomm.com
> 
> ---
> Hrishabh Rajput (2):
>        firmware: qcom: scm: Register gunyah watchdog device
>        watchdog: Add driver for Gunyah Watchdog
> 
>   MAINTAINERS                      |   1 +
>   drivers/firmware/qcom/qcom_scm.c |  53 ++++++++
>   drivers/watchdog/Kconfig         |  13 ++
>   drivers/watchdog/Makefile        |   1 +
>   drivers/watchdog/gunyah_wdt.c    | 260 +++++++++++++++++++++++++++++++++++++++
>   5 files changed, 328 insertions(+)
> ---
> base-commit: e9a6fb0bcdd7609be6969112f3fbfcce3b1d4a7c
> change-id: 20250903-gunyah_watchdog-2d2649438e29
> 
> Best regards,

Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-QRD
Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-HDK

Thanks,
Neil