From: Rob Herring <robh@kernel.org>
To: Hrishabh Rajput <hrishabh.rajput@oss.qualcomm.com>
Cc: Bjorn Andersson <andersson@kernel.org>,
Konrad Dybcio <konradybcio@kernel.org>,
Wim Van Sebroeck <wim@linux-watchdog.org>,
Guenter Roeck <linux@roeck-us.net>,
Krzysztof Kozlowski <krzk+dt@kernel.org>,
Conor Dooley <conor+dt@kernel.org>,
linux-arm-msm@vger.kernel.org, linux-watchdog@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] Add support for Gunyah Watchdog
Date: Wed, 3 Sep 2025 19:10:14 -0500 [thread overview]
Message-ID: <20250904001014.GA3405605-robh@kernel.org> (raw)
In-Reply-To: <20250903-gunyah_watchdog-v1-0-3ae690530e4b@oss.qualcomm.com>
On Wed, Sep 03, 2025 at 07:33:58PM +0000, Hrishabh Rajput 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.
EFI provides a standard watchdog interface. Why can't you use that?
> The SMC-based watchdog follows ARM's SMC Calling Convention (SMCCC)
> version 1.1 and uses Vendor Specific Hypervisor Service Calls space.
Is a watchdog really a hypervisor service? Couldn't a non-virtualized
OS want to call a watchdog (in secure mode) as well? But I don't know
how the SMCCC call space is divided up...
> 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.
Shouldn't system restart be handled by PSCI?
Why can't you probe by trying to see if watchdog smc call succeeds to
see if there is a watchdog? Then you don't need DT for it.
Rob
next prev parent reply other threads:[~2025-09-04 0:10 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-03 19:33 [PATCH 0/2] Add support for Gunyah Watchdog Hrishabh Rajput via B4 Relay
2025-09-03 19:33 ` [PATCH 1/2] dt-bindings: Add binding for gunyah watchdog Hrishabh Rajput via B4 Relay
2025-09-03 23:27 ` Rob Herring (Arm)
2025-09-04 9:52 ` Krzysztof Kozlowski
2025-09-04 10:16 ` Pavan Kondeti
2025-09-04 10:49 ` Krzysztof Kozlowski
2025-09-04 10:59 ` Krzysztof Kozlowski
2025-09-04 12:29 ` Pavan Kondeti
2025-09-04 13:07 ` Hrishabh Rajput
2025-09-04 13:17 ` Krzysztof Kozlowski
2025-09-04 19:03 ` Hrishabh Rajput
2025-09-03 19:34 ` [PATCH 2/2] watchdog: Add driver for Gunyah Watchdog Hrishabh Rajput via B4 Relay
2025-09-03 20:13 ` Bjorn Andersson
2025-09-04 11:40 ` Hrishabh Rajput
2025-09-04 13:47 ` Bjorn Andersson
2025-09-04 17:11 ` Pavan Kondeti
2025-09-05 9:19 ` Konrad Dybcio
2025-09-04 0:10 ` Rob Herring [this message]
2025-09-04 11:31 ` [PATCH 0/2] Add support " Konrad Dybcio
2025-09-04 22:51 ` Rob Herring
2025-09-05 0:00 ` Pavan Kondeti
2025-09-05 10:18 ` Konrad Dybcio
2025-09-08 5:49 ` Pavan Kondeti
2025-09-04 14:39 ` Hrishabh Rajput
2025-09-04 7:13 ` Neil Armstrong
2025-09-04 9:18 ` Pavan Kondeti
2025-09-04 13:53 ` Bjorn Andersson
2025-09-04 17:05 ` Pavan Kondeti
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