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arm64: dts: allwinner: wirenboard85x: park CPU at a boot-safe OPP across suspend #362

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arm64: dts: allwinner: wirenboard85x: park CPU at a boot-safe OPP across suspend #362

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17 changes: 17 additions & 0 deletions arch/arm64/boot/dts/allwinner/sun50i-h616-wirenboard85x.dtsi
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Original file line number Diff line number Diff line change
Expand Up @@ -1662,3 +1662,20 @@
&iommu {
status = "okay";
};

/*
* Suspend-to-off contract with the boot firmware: on resume, U-Boot
* SPL's board init runs before the resume branch and programs VDD-CPU
* to its 0.90 V cold-boot value (CONFIG_AXP_DCDC2_VOLT), and BL31 then
* restores the PLL frequency the kernel parked at. The OPP the kernel
* parks at across suspend must therefore be safe at 0.90 V on every
* speed bin. 480 MHz is 0.90 V-rated and bin-universal
* (opp-supported-hw 0x1f). The primary fix lives in BL31 (it restores
* the recorded voltage before the recorded frequency); this is the
* kernel-side belt in case firmware and kernel ever skew.
*/
&cpu_opp_table {
opp-480000000 {
opp-suspend;
};
};