linux-kernel - Re: [PATCH 33/33] arm64: dts: ti: k3-j7*-ti-ipc-firmware: Switch MCU R5F cluster to Split-mode

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Message-ID: <9a3f4271-ada2-48aa-b99d-023619ec5e12@ti.com>
Date: Fri, 15 Aug 2025 10:48:35 -0500
From: Andrew Davis <afd@...com>
To: Beleswar Padhi <b-padhi@...com>, <nm@...com>, <vigneshr@...com>,
        <kristo@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
        <conor+dt@...nel.org>
CC: <u-kumar1@...com>, <hnagalla@...com>, <jm@...com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 33/33] arm64: dts: ti: k3-j7*-ti-ipc-firmware: Switch MCU
 R5F cluster to Split-mode

On 8/14/25 5:38 PM, Beleswar Padhi wrote:
> Several TI K3 SoCs like J7200, J721E, J721S2, J784S4 and J742S2 have a
> R5F cluster in the MCU domain which is configured for LockStep mode at
> the moment. The necessary support to use MCU R5F cluster in split mode
> was added in the bootloader. And the TI IPC firmware for the split
> processors is already available public.
> 
> Therefore, Switch this R5F cluster to Split mode by default in all the
> boards using TI IPC Firmware config (k3-j7*-ti-ipc-firmware). This
> gives out an extra general purpose R5F core free to run any applications
> as required. Lockstep mode remains default in the SoC level dtsi, so
> downstream board dts which do not use TI IPC Firmware config should not
> be impacted by this switch.
> 
> Users who prefer to use the fault-tolerant lockstep mode with TI IPC
> firmware config, can do that by setting `ti,cluster-mode` property to 1.

What a user prefers and other configuration like that does not belong
in devicetree, which should only describe the hardware.

Configuration should be done using the normal methods, like kernel
cmdline, module params, ioctls, etc.. Maybe we can even set the mode
based on some signal in the firmware itself, like in the resource table.

Andrew

> 
> Signed-off-by: Beleswar Padhi <b-padhi@...com>
> ---
>   arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi             | 1 +
>   arch/arm64/boot/dts/ti/k3-j721e-ti-ipc-firmware.dtsi             | 1 +
>   arch/arm64/boot/dts/ti/k3-j721s2-ti-ipc-firmware.dtsi            | 1 +
>   .../boot/dts/ti/k3-j784s4-j742s2-ti-ipc-firmware-common.dtsi     | 1 +
>   4 files changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi b/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi
> index 8eff7bd2e771..ddf3cd899d0e 100644
> --- a/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi
> @@ -94,6 +94,7 @@ &main_timer2 {
>   
>   &mcu_r5fss0 {
>   	status = "okay";
> +	ti,cluster-mode = <0>;
>   };
>   
>   &mcu_r5fss0_core0 {
> diff --git a/arch/arm64/boot/dts/ti/k3-j721e-ti-ipc-firmware.dtsi b/arch/arm64/boot/dts/ti/k3-j721e-ti-ipc-firmware.dtsi
> index 5b3fa95aed76..57890a3b38a2 100644
> --- a/arch/arm64/boot/dts/ti/k3-j721e-ti-ipc-firmware.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-j721e-ti-ipc-firmware.dtsi
> @@ -211,6 +211,7 @@ &main_timer15 {
>   };
>   
>   &mcu_r5fss0 {
> +	ti,cluster-mode = <0>;
>   	status = "okay";
>   };
>   
> diff --git a/arch/arm64/boot/dts/ti/k3-j721s2-ti-ipc-firmware.dtsi b/arch/arm64/boot/dts/ti/k3-j721s2-ti-ipc-firmware.dtsi
> index 40c9f2b64e7e..7ee8a8615246 100644
> --- a/arch/arm64/boot/dts/ti/k3-j721s2-ti-ipc-firmware.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-j721s2-ti-ipc-firmware.dtsi
> @@ -179,6 +179,7 @@ &main_timer5 {
>   };
>   
>   &mcu_r5fss0 {
> +	ti,cluster-mode = <0>;
>   	status = "okay";
>   };
>   
> diff --git a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-ti-ipc-firmware-common.dtsi b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-ti-ipc-firmware-common.dtsi
> index b5a4496a05bf..e12fa55a4df0 100644
> --- a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-ti-ipc-firmware-common.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-ti-ipc-firmware-common.dtsi
> @@ -254,6 +254,7 @@ &main_timer9 {
>   };
>   
>   &mcu_r5fss0 {
> +	ti,cluster-mode = <0>;
>   	status = "okay";
>   };
>