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

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Message-ID: <ec0dc13a-30f7-44a0-9a4a-5f44eccd3933@quicinc.com>
Date: Thu, 4 Sep 2025 14:48:03 +0530
From: Pavan Kondeti <pavan.kondeti@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>
Cc: 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>, linux-arm-msm@...r.kernel.org,
        linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Add support for Gunyah Watchdog

On Thu, Sep 04, 2025 at 09:13:23AM +0200, Neil Armstrong wrote:
> On 03/09/2025 21:33, 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. The driver supports start/stop
> > operations, timeout and pretimeout configuration, pretimeout interrupt
> > handling and system restart via watchdog.
> > 
> > This series is tested on SM8750 platform.
> 
> Would this driver work on older platforms like SM8550 & SM8650 ?
> 

This driver should work on 8550 and 8650 too as long as the hypervisor
overlay is applied to the device tree which happens in the bootloader.

I remember porting some hypercalls to 8550 upstream kernel to induce the
watchdog bite in panic to collect the dumps. one of the biggest benefit
w/ this driver is that we can collect dumps upon kernel panic. since we
won't be able to pet the watchdog upon panic, the bite would eventually
happens and device enters dump collection mode.

Thanks,
Pavan