[PATCH v3 4/7] dts: qcs615-ride-u-boot.dtsi: Add reboot-mode support

[Quentin Schulz]

Hi Aswin,

On 3/30/26 7:14 PM, Aswin Murugan wrote:
> The PM8150 PMIC on this platform uses the older PON (Power On) register
> architecture rather than dedicated SDAM regions found in newer PMIC
> generations. To enable reboot-mode functionality with the unified
> NVMEM-based approach, add a compatibility wrapper that exposes PON
> registers through the SDAM NVMEM interface.
> 
> Add device tree configuration:
> - NVMEM node with compatible "qcom,spmi-sdam" wrapping PON registers
> - Uses 'ranges' property to map the PON register block at offset 0x800
> - NVMEM cell at offset 0x8F (PON_SOFT_RB_SPARE register)
> - 7-bit field (bits [7:1]) for reboot reason, preserving bit 0
> - Mode mappings: bootloader=0x02, recovery=0x01
> 
> This wrapper allows the SDAM NVMEM driver to access PON registers
> transparently, providing a unified interface for both PON-based (older)
> and SDAM-based (newer) PMIC generations.
> 
> The PON_SOFT_RB_SPARE register persists across warm resets and is
> automatically cleared on power cycle.
> 
> Signed-off-by: Aswin Murugan <aswin.murugan at oss.qualcomm.com>
> ---
> Changes in v3:
> 1. No change in v3
> ---
>   arch/arm/dts/qcs615-ride-u-boot.dtsi | 26 ++++++++++++++++++++++++++
>   1 file changed, 26 insertions(+)
> 
> diff --git a/arch/arm/dts/qcs615-ride-u-boot.dtsi b/arch/arm/dts/qcs615-ride-u-boot.dtsi
> index 68fffc70fcb..50784807cf4 100644
> --- a/arch/arm/dts/qcs615-ride-u-boot.dtsi
> +++ b/arch/arm/dts/qcs615-ride-u-boot.dtsi
> @@ -11,4 +11,30 @@
>   		      <0x0 0xc0000000 0x0 0xc0000000>,
>   		      <0x1 0x80000000 0x1 0x00000000>;
>   	};
> +
> +	reboot-mode {
> +		compatible = "nvmem-reboot-mode";
> +		nvmem-cells = <&reboot_reason>;
> +		nvmem-cell-names = "reboot-mode";
> +
> +		mode-bootloader = <0x02>;
> +		mode-recovery   = <0x01>;
> +	};
> +};
> +
> +&pm8150_0 {
> +	/* Virtual NVMEM node for PON-based reboot reason storage */
> +	nvram at 800 {
> +		compatible = "qcom,spmi-sdam";
> +		reg = <0x800>;
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		ranges = <0x00 0x800 0x100>;
> +
> +		/* Reboot reason cell at PON_SOFT_RB_SPARE (0x88F) */
> +		reboot_reason: reboot-reason at 8f {
> +			reg = <0x8f 0x1>;
> +			bits = <0x01 0x07>;
> +		};
> +	};

How is that U-Boot-specific? We're trying to have as little as possible 
in U-Boot-specific Device Trees and there exists a DTS in upstream 
Linux. I see nvmem-reboot-mode has an upstream binding and driver and is 
defined in a few other Qcom DTSIs as well. Same for qcom,spmi-sdam node. 
So it'd be nice to motivate why this cannot be upstreamed to the Linux 
kernel.

Cheers,
Quentin