Re: [PATCH v2] watchdog: Add driver for Gunyah Watchdog

[Guenter Roeck]

On 10/6/25 00:37, Hrishabh Rajput via B4 Relay wrote:
> From: Hrishabh Rajput <hrishabh.rajput@xxxxxxxxxxxxxxxx>
>
> On Qualcomm SoCs running under the Gunyah hypervisor, access to watchdog
> through MMIO is not available on all platforms. 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 Gunyah is not present or Gunyah emulates MMIO-based watchdog, we
> expect MMIO watchdog device to be present in the devicetree. If we
> detect this device node, we don't proceed ahead. Otherwise, we go ahead
> and invoke GUNYAH_WDT_STATUS SMC to initiate the discovery of the
> SMC-based watchdog.
>
> Add driver to support the SMC-based watchdog provided by the Gunyah
> Hypervisor. module_exit() is intentionally not implemented as this
> driver is intended to be a persistent module.
>
> Signed-off-by: Hrishabh Rajput <hrishabh.rajput@xxxxxxxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxx/
>
> [2]
> https://github.com/quic/gunyah-hypervisor
> ---
> Changes in v2:
> - Move away from platform driver model since the devicetree overlay does
>    not happen by default.

This is just wrong. Platform drivers do not depend on devicetree. I am not even
going to review the rest of the driver.

Guenter