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 <[email protected]>
---
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@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@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
