[PATCH] arm64: versal-net: Add retention state for cpu idle
Jay Buddhabhatti
jay.buddhabhatti at amd.com
Mon Jul 27 05:18:42 PDT 2026
Remove the sleep state and replace it with a retention state for CPU idle.
The sleep state powers down the CPU core, and the wake-up time cannot be
guaranteed because the firmware may be busy handling other tasks at the time
of the wake-up request. This leads to unpredictable and potentially high
wake-up latency during CPU idle.
Replace the sleep state with a retention state to avoid this dependency on
firmware. The retention state uses a PSCI suspend parameter of 0: the
core simply executes WFI and retains its context without being powered off.
Since wake-up from WFI is handled entirely in hardware, it is effectively
immediate (a few cycles) and does not depend on firmware availability.
As the core is not powered down, the local timer is retained and
"local-timer-stop" is dropped. The entry/exit latency and min-residency
are set to the nominal minimum (1 us), allowing the cpuidle governor to
select the state even for very short idle windows.
Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti at amd.com>
---
arch/arm64/boot/dts/xilinx/versal-net.dtsi | 43 +++++++++++-----------
1 file changed, 21 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/boot/dts/xilinx/versal-net.dtsi b/arch/arm64/boot/dts/xilinx/versal-net.dtsi
index 15f767608e67..792bed588ae1 100644
--- a/arch/arm64/boot/dts/xilinx/versal-net.dtsi
+++ b/arch/arm64/boot/dts/xilinx/versal-net.dtsi
@@ -103,7 +103,7 @@ cpu0: cpu at 0 {
enable-method = "psci";
reg = <0>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -133,7 +133,7 @@ cpu100: cpu at 100 {
enable-method = "psci";
reg = <0x100>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -163,7 +163,7 @@ cpu200: cpu at 200 {
enable-method = "psci";
reg = <0x200>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -193,7 +193,7 @@ cpu300: cpu at 300 {
enable-method = "psci";
reg = <0x300>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -223,7 +223,7 @@ cpu10000: cpu at 10000 {
enable-method = "psci";
reg = <0x10000>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -253,7 +253,7 @@ cpu10100: cpu at 10100 {
enable-method = "psci";
reg = <0x10100>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -283,7 +283,7 @@ cpu10200: cpu at 10200 {
enable-method = "psci";
reg = <0x10200>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -313,7 +313,7 @@ cpu10300: cpu at 10300 {
enable-method = "psci";
reg = <0x10300>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -343,7 +343,7 @@ cpu20000: cpu at 20000 {
enable-method = "psci";
reg = <0x20000>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -373,7 +373,7 @@ cpu20100: cpu at 20100 {
enable-method = "psci";
reg = <0x20100>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -403,7 +403,7 @@ cpu20200: cpu at 20200 {
enable-method = "psci";
reg = <0x20200>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -433,7 +433,7 @@ cpu20300: cpu at 20300 {
enable-method = "psci";
reg = <0x20300>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -463,7 +463,7 @@ cpu30000: cpu at 30000 {
enable-method = "psci";
reg = <0x30000>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -493,7 +493,7 @@ cpu30100: cpu at 30100 {
enable-method = "psci";
reg = <0x30100>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -523,7 +523,7 @@ cpu30200: cpu at 30200 {
enable-method = "psci";
reg = <0x30200>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -553,7 +553,7 @@ cpu30300: cpu at 30300 {
enable-method = "psci";
reg = <0x30300>;
operating-points-v2 = <&cpu_opp_table>;
- cpu-idle-states = <&CPU_SLEEP_0>;
+ cpu-idle-states = <&CPU_RETENTION_0>;
d-cache-size = <0x10000>; /* 64kB */
d-cache-line-size = <64>;
/* 4 ways set associativity */
@@ -636,13 +636,12 @@ llc: l4-cache { /* LLC inside CMN */
idle-states {
entry-method = "psci";
- CPU_SLEEP_0: cpu-sleep-0 {
+ CPU_RETENTION_0: cpu-retention-0 {
compatible = "arm,idle-state";
- arm,psci-suspend-param = <0x40000000>;
- local-timer-stop;
- entry-latency-us = <300>;
- exit-latency-us = <600>;
- min-residency-us = <10000>;
+ arm,psci-suspend-param = <0>;
+ entry-latency-us = <1>;
+ exit-latency-us = <1>;
+ min-residency-us = <1>;
};
};
};
--
2.34.1
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