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

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Message-ID: <qd22epqcu7sdza6jrl3tj7pceohqh3clsywv44uau5bvszux54@ajqseswmwf6x>
Date: Thu, 4 Sep 2025 08:53:14 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Pavan Kondeti <pavan.kondeti@....qualcomm.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, 
	hrishabh.rajput@....qualcomm.com, 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 02:48:03PM +0530, Pavan Kondeti wrote:
> 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.
> 

You have easy access to 8550 and 8650 MTP/QRD devices, please give us a
definitive answer.

Regards,
Bjorn

> 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