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

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Message-ID: <91002189-9d9e-48a2-8424-c42705fed3f8@quicinc.com>
Date: Thu, 4 Sep 2025 22:35:57 +0530
From: Pavan Kondeti <pavan.kondeti@....qualcomm.com>
To: Bjorn Andersson <andersson@...nel.org>
Cc: Pavan Kondeti <pavan.kondeti@....qualcomm.com>,
        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 08:53:14AM -0500, Bjorn Andersson wrote:
> 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.
> 

Thanks for asking this question. I believe the overlay part needs some
discussion here.

I have tried this series on 8550 MTP. The overlay failed, so watchdog
device did not probe. same is the case with 8750 too. It works only
after applying this patch. I will test and report my observation on 8650
later.

diff --git a/arch/arm64/boot/dts/qcom/Makefile b/arch/arm64/boot/dts/qcom/Makefile
index 140b0b2abfb5..b200e8faa6df 100644
--- a/arch/arm64/boot/dts/qcom/Makefile
+++ b/arch/arm64/boot/dts/qcom/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
+DTC_FLAGS := -@
 dtb-$(CONFIG_ARCH_QCOM)	+= apq8016-sbc.dtb
 
 apq8016-sbc-usb-host-dtbs	:= apq8016-sbc.dtb apq8016-sbc-usb-host.dtbo
diff --git a/arch/arm64/boot/dts/qcom/sm8550.dtsi b/arch/arm64/boot/dts/qcom/sm8550.dtsi
index eac8de4005d8..7536b1a4ec97 100644
--- a/arch/arm64/boot/dts/qcom/sm8550.dtsi
+++ b/arch/arm64/boot/dts/qcom/sm8550.dtsi
@@ -328,7 +328,7 @@ cluster_sleep_1: cluster-sleep-1 {
 	};
 
 	firmware {
-		scm: scm {
+		scm: qcom_scm {
 			compatible = "qcom,scm-sm8550", "qcom,scm";
 			qcom,dload-mode = <&tcsr 0x19000>;
 			interconnects = <&aggre2_noc MASTER_CRYPTO 0 &mc_virt SLAVE_EBI1 0>;
@@ -4855,6 +4855,9 @@ compute-cb@8 {
 				};
 			};
 		};
+
+		qcom_tzlog: tz-log {
+		};
 	};
 
 	thermal-zones {
@@ -5913,7 +5916,7 @@ trip-point2 {
 		};
 	};
 
-	timer {
+	arch_timer: timer {
 		compatible = "arm,armv8-timer";
 		interrupts = <GIC_PPI 13 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>,
 			     <GIC_PPI 14 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>,


Thanks,
Pavan