linux-kernel - [PATCH v2 1/1] arm64: dts: xilinx: fix zynqmp opp-table-cpu

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Message-ID: <20251103065344.4022482-1-neal.frager@amd.com>
Date: Mon, 3 Nov 2025 06:53:44 +0000
From: Neal Frager <neal.frager@....com>
To: <gregkh@...uxfoundation.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>, <git@....com>
CC: <michal.simek@....com>, <jguittet@...ekio.com>,
	<jay.buddhabhatti@....com>, <arun.balaji.kannan@....com>,
	<senthilnathan.thangaraj@....com>, <thomas.hommel@...rson.com>,
	<micheal.saleab@....com>, <robh@...nel.org>, <krzk+dt@...nel.org>,
	<conor+dt@...nel.org>, Neal Frager <neal.frager@....com>
Subject: [PATCH v2 1/1] arm64: dts: xilinx: fix zynqmp opp-table-cpu

Since the following commit, the zynqmp clk driver uses the common
divider_round_rate() when determining the appropriate clock divider for a
requested clock frequency:
https://github.com/torvalds/linux/commit/1fe15be1fb613534ecbac5f8c3f8744f757d237d

This means that the typical parent clock rate will be 1200000000 based on the
zynqmp pll configuration. If the current zynqmp.dtsi opp-hz values are used,
this will mean the divider calculations are always slightly above the correct
integer divider value meaning they will get rounded up to a divider value
which is one too high. The result of this issue is that the cpu clock speed
will always be one opp lower than the requested clock rate.

For example, the following will occur when requesting 1.2 GHz with the current
zynqmp.dtsi:

root@...qmp:/sys/kernel/tracing# cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies
299999 399999 599999 1199999
root@...qmp:/ # echo 1200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed
root@...qmp:/ # cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq
600000

To fix this issue, this patch updates the zynqmp opp-table-cpu, so the clock
rates are calculated correctly.

root@...qmp:/sys/kernel/tracing# cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies
300000 400000 600000 1200000
root@...qmp:/ # echo 1200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed
root@...qmp:/ # cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq
1200000

Signed-off-by: Neal Frager <neal.frager@....com>
---
V1->V2:
- The clock-latency-ns and opp-microvolt values did not change, so simplify
  the patch by only changing the opp-hz values in decimal format.
---
 arch/arm64/boot/dts/xilinx/zynqmp.dtsi | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/boot/dts/xilinx/zynqmp.dtsi b/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
index 938b014ca923..dd9bd39f61e8 100644
--- a/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
+++ b/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
@@ -103,23 +103,23 @@ CPU_SLEEP_0: cpu-sleep-0 {
 	cpu_opp_table: opp-table-cpu {
 		compatible = "operating-points-v2";
 		opp-shared;
-		opp00 {
-			opp-hz = /bits/ 64 <1199999988>;
+		opp-1200000000 {
+			opp-hz = /bits/ 64 <1200000000>;
 			opp-microvolt = <1000000>;
 			clock-latency-ns = <500000>;
 		};
-		opp01 {
-			opp-hz = /bits/ 64 <599999994>;
+		opp-600000000 {
+			opp-hz = /bits/ 64 <600000000>;
 			opp-microvolt = <1000000>;
 			clock-latency-ns = <500000>;
 		};
-		opp02 {
-			opp-hz = /bits/ 64 <399999996>;
+		opp-400000000 {
+			opp-hz = /bits/ 64 <400000000>;
 			opp-microvolt = <1000000>;
 			clock-latency-ns = <500000>;
 		};
-		opp03 {
-			opp-hz = /bits/ 64 <299999997>;
+		opp-300000000 {
+			opp-hz = /bits/ 64 <300000000>;
 			opp-microvolt = <1000000>;
 			clock-latency-ns = <500000>;
 		};
-- 
2.25.1