[PATCH 0/2] Exynos850: Add ACPM node and enable cpufreq

[PATCH 0/2] Exynos850: Add ACPM node and enable cpufreq

[Alexey Klimov]

This series adds the ACPM IPC firmware node and CPUs operating performance
points for the Exynos850 SoC, switching CPU clock sources to the ACPM DVFS
clocks to enable cpufreq. Exynos850 has two clusters with four Cortex-A55
cores each with identical OPPs.

In theory, we could have two OPPs above known nominal max frequency (2Ghz)
but in practice the board becomes unstable with fully loaded CPU-bound
tasks and hangs pretty quickly on OPPs above 2 Ghz:

	opp-2106000000 {
		opp-hz = /bits/ 64 <2106000000>;
		opp-microvolt = <1106250>;
		clock-latency-ns = <500000>;
	};

	opp-2210000000 {
		opp-hz = /bits/ 64 <2210000000>;
		opp-microvolt = <1181250>;
		clock-latency-ns = <500000>;
	};

with random data aborts and illegal instructions. Maybe SoC can survive
short bursts to these frequencies but this requires a bit more messing
around with cpufreq_dt.

Also, it is currently unstable on 2.002 GHz OPP as well so this one
excluded from the series too:

	opp-2002000000 {
		opp-hz = /bits/ 64 <2002000000>;
		opp-microvolt = <1050000>;
		clock-latency-ns = <500000>;
	};

with the same symptoms but takes much longer (~1..2 hr) to reproduce on
E850-96 WinLink board.

Sustained testing overnight confirmed stability up to 1.846 GHz
(opp-1846000000). Higher OPPs are omitted for now and can be evaluated
when we will have thermal zones.

The dependency for this series is:
https://lore.kernel.org/linux-samsung-soc/20260929-exynos850-acpm-firmware-support-v3-0-473a69fc8a3d@linaro.org/

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
Alexey Klimov (2):
      arm64: dts: exynos850: Add ACPM firmware node
      arm64: dts: exynos850: Add operating points for CPUs and enable cpufreq

 arch/arm64/boot/dts/exynos/exynos850.dtsi | 237 +++++++++++++++++++++++++++++-
 1 file changed, 233 insertions(+), 4 deletions(-)
---
base-commit: 5a956dde5526a634dca7ccad27c051ebcc306089
change-id: 20260929-exynos850-acpm-node-cpufreq-33819039cf43
prerequisite-message-id: 20260929-exynos850-acpm-firmware-support-v3-0-473a69fc8a3d@linaro.org
prerequisite-patch-id: 5a3c87e368d6bac968f16a0e56fcff5eaec60dea
prerequisite-patch-id: 8d6d1564a919eca361aef19af5dbe1cf3205198e

Best regards,
-- 
Alexey Klimov <alexey.klimov@linaro.org>

[PATCH 1/2] arm64: dts: exynos850: Add ACPM firmware node

[Alexey Klimov]

Add the ACPM firmware node with cpucl0 and cpucl1 clocks. ACPM firmware
protocol provides interface for all client drivers to actually use
features exposed by the APM co-processor.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 arch/arm64/boot/dts/exynos/exynos850.dtsi | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
index 8a4771899a8e..91c6cee8f483 100644
--- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
+++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
@@ -11,6 +11,7 @@
  */
 
 #include <dt-bindings/clock/exynos850.h>
+#include <dt-bindings/clock/samsung,exynos850-acpm.h>
 #include <dt-bindings/interrupt-controller/arm-gic.h>
 #include <dt-bindings/soc/samsung,exynos-usi.h>
 
@@ -170,6 +171,18 @@ timer: timer {
 		     <GIC_PPI 10 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>;
 	};
 
+	firmware {
+		acpm_ipc: power-management {
+			compatible = "samsung,exynos850-acpm-ipc";
+			mboxes = <&ap2apm_mailbox>;
+			shmem = <&apm_sram>;
+			clocks = <&cmu_cpucl0 CLK_FOUT_CPUCL0_PLL>,
+				 <&cmu_cpucl1 CLK_FOUT_CPUCL1_PLL>;
+			clock-names = "cpucl0", "cpucl1";
+			#clock-cells = <1>;
+		};
+	};
+
 	soc: soc@0 {
 		compatible = "simple-bus";
 		#address-cells = <1>;

-- 
2.51.0

Re: [PATCH 1/2] arm64: dts: exynos850: Add ACPM firmware node

[Tudor Ambarus]

Hi, Alexey,

On 9/29/26 6:10 AM, Alexey Klimov wrote:
> Add the ACPM firmware node with cpucl0 and cpucl1 clocks. ACPM firmware
> protocol provides interface for all client drivers to actually use
> features exposed by the APM co-processor.
> 
> Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
> ---
>  arch/arm64/boot/dts/exynos/exynos850.dtsi | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
> index 8a4771899a8e..91c6cee8f483 100644
> --- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
> +++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
> @@ -11,6 +11,7 @@
>   */
>  
>  #include <dt-bindings/clock/exynos850.h>
> +#include <dt-bindings/clock/samsung,exynos850-acpm.h>
>  #include <dt-bindings/interrupt-controller/arm-gic.h>
>  #include <dt-bindings/soc/samsung,exynos-usi.h>
>  
> @@ -170,6 +171,18 @@ timer: timer {
>  		     <GIC_PPI 10 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>;
>  	};
>  
> +	firmware {
> +		acpm_ipc: power-management {
> +			compatible = "samsung,exynos850-acpm-ipc";
> +			mboxes = <&ap2apm_mailbox>;
> +			shmem = <&apm_sram>;
> +			clocks = <&cmu_cpucl0 CLK_FOUT_CPUCL0_PLL>,
> +				 <&cmu_cpucl1 CLK_FOUT_CPUCL1_PLL>;

Why do you describe these clocks?

Thanks,
ta

> +			clock-names = "cpucl0", "cpucl1";
> +			#clock-cells = <1>;
> +		};
> +	};
> +
>  	soc: soc@0 {
>  		compatible = "simple-bus";
>  		#address-cells = <1>;
> 

Re: [PATCH 1/2] arm64: dts: exynos850: Add ACPM firmware node

[Alexey Klimov]

Hi Tudor,

On Tue Sep 29, 2026 at 10:02 AM BST, Tudor Ambarus wrote:
> Hi, Alexey,
> On 9/29/26 6:10 AM, Alexey Klimov wrote:
>> Add the ACPM firmware node with cpucl0 and cpucl1 clocks. ACPM firmware
>> protocol provides interface for all client drivers to actually use
>> features exposed by the APM co-processor.
>> 
>> Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
>> ---
>>  arch/arm64/boot/dts/exynos/exynos850.dtsi | 13 +++++++++++++
>>  1 file changed, 13 insertions(+)
>> 
>> diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
>> index 8a4771899a8e..91c6cee8f483 100644
>> --- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
>> +++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
>> @@ -11,6 +11,7 @@
>>   */
>>  
>>  #include <dt-bindings/clock/exynos850.h>
>> +#include <dt-bindings/clock/samsung,exynos850-acpm.h>
>>  #include <dt-bindings/interrupt-controller/arm-gic.h>
>>  #include <dt-bindings/soc/samsung,exynos-usi.h>
>>  
>> @@ -170,6 +171,18 @@ timer: timer {
>>  		     <GIC_PPI 10 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>;
>>  	};
>>  
>> +	firmware {
>> +		acpm_ipc: power-management {
>> +			compatible = "samsung,exynos850-acpm-ipc";
>> +			mboxes = <&ap2apm_mailbox>;
>> +			shmem = <&apm_sram>;
>> +			clocks = <&cmu_cpucl0 CLK_FOUT_CPUCL0_PLL>,
>> +				 <&cmu_cpucl1 CLK_FOUT_CPUCL1_PLL>;
>
> Why do you describe these clocks?

>> +			clock-names = "cpucl0", "cpucl1";

To link these clocks with ACPM clocks from this list:
(file drivers/clk/samsung/clk-acpm.c)

static const struct acpm_clk_variant exynos850_acpm_clks[] = {
	ACPM_CLK("mif"),
	ACPM_CLK("int"),
	ACPM_CLK("cpucl0"),
	ACPM_CLK("cpucl1"),
	ACPM_CLK("g3d"),
	ACPM_CLK("aud"),
	ACPM_CLK("cam"),
	ACPM_CLK("disp"),
	ACPM_CLK("cp"),
};

Eventually to have some sensible/working ->recalc_rate() for ACPM
cpucl{0,1} clocks.

Which is needed, for instance, for cpufreq_dt because it registers with:

static struct cpufreq_driver dt_cpufreq_driver = {
        .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK |
                 CPUFREQ_IS_COOLING_DEV,

Don't know if it answers the question (if I understood it correctly)?

Best regards,
Alexey

[PATCH 2/2] arm64: dts: exynos850: Add operating points for CPUs and enable cpufreq

[Alexey Klimov]

Exynos850 has two clusters with four Cortex-A55 cores each. The OPPs are
identical for both clusters.
Add OPPs for both clusters and replace cpu clocks with ACPM
EXYNOS850_CLK_ACPM_DVFS_CPUCL{0,1} clocks.

The maximum nominal frequency should be 2.002 Ghz but at this point the
following OPP is not added here:

	opp-2002000000 {
		opp-hz = /bits/ 64 <2002000000>;
		opp-microvolt = <1050000>;
		clock-latency-ns = <500000>;
	};

due to stability issues. Testing on a fully loaded system with CPU-bound
tasks triggers data aborts and illegal instruction errors at 2.002 GHz
after 1-2 hours of such stress testing.
Running the same workload overnight on a CPUs fixed at previous OPP didn't
lead to any issues so opp-1846000000 is currentlly the highest one as it is
considered safe.

Higher OPPs can be re-evaluated once thermal support is implemented.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 arch/arm64/boot/dts/exynos/exynos850.dtsi | 224 +++++++++++++++++++++++++++++-
 1 file changed, 220 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
index 91c6cee8f483..36501e5903f8 100644
--- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
+++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
@@ -100,8 +100,9 @@ cpu0: cpu@0 {
 			compatible = "arm,cortex-a55";
 			reg = <0x0>;
 			enable-method = "psci";
-			clocks = <&cmu_cpucl0 CLK_CLUSTER0_SCLK>;
-			clock-names = "cluster0_clk";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL0>;
+			clock-names = "cpucl0";
+			operating-points-v2 = <&cpucl0_opp_table>;
 		};
 
 		cpu1: cpu@1 {
@@ -109,6 +110,8 @@ cpu1: cpu@1 {
 			compatible = "arm,cortex-a55";
 			reg = <0x1>;
 			enable-method = "psci";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL0>;
+			operating-points-v2 = <&cpucl0_opp_table>;
 		};
 
 		cpu2: cpu@2 {
@@ -116,6 +119,8 @@ cpu2: cpu@2 {
 			compatible = "arm,cortex-a55";
 			reg = <0x2>;
 			enable-method = "psci";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL0>;
+			operating-points-v2 = <&cpucl0_opp_table>;
 		};
 
 		cpu3: cpu@3 {
@@ -123,6 +128,8 @@ cpu3: cpu@3 {
 			compatible = "arm,cortex-a55";
 			reg = <0x3>;
 			enable-method = "psci";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL0>;
+			operating-points-v2 = <&cpucl0_opp_table>;
 		};
 
 		cpu4: cpu@100 {
@@ -130,8 +137,9 @@ cpu4: cpu@100 {
 			compatible = "arm,cortex-a55";
 			reg = <0x100>;
 			enable-method = "psci";
-			clocks = <&cmu_cpucl1 CLK_CLUSTER1_SCLK>;
-			clock-names = "cluster1_clk";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL1>;
+			clock-names = "cpucl1";
+			operating-points-v2 = <&cpucl1_opp_table>;
 		};
 
 		cpu5: cpu@101 {
@@ -139,6 +147,8 @@ cpu5: cpu@101 {
 			compatible = "arm,cortex-a55";
 			reg = <0x101>;
 			enable-method = "psci";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL1>;
+			operating-points-v2 = <&cpucl1_opp_table>;
 		};
 
 		cpu6: cpu@102 {
@@ -146,6 +156,8 @@ cpu6: cpu@102 {
 			compatible = "arm,cortex-a55";
 			reg = <0x102>;
 			enable-method = "psci";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL1>;
+			operating-points-v2 = <&cpucl1_opp_table>;
 		};
 
 		cpu7: cpu@103 {
@@ -153,6 +165,210 @@ cpu7: cpu@103 {
 			compatible = "arm,cortex-a55";
 			reg = <0x103>;
 			enable-method = "psci";
+			clocks = <&acpm_ipc EXYNOS850_CLK_ACPM_DVFS_CPUCL1>;
+			operating-points-v2 = <&cpucl1_opp_table>;
+		};
+	};
+
+	cpucl0_opp_table: opp-table-0 {
+		compatible = "operating-points-v2";
+		opp-shared;
+
+		opp-130000000 {
+			opp-hz = /bits/ 64 <130000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-182000000 {
+			opp-hz = /bits/ 64 <182000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-247000000 {
+			opp-hz = /bits/ 64 <247000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-351000000 {
+			opp-hz = /bits/ 64 <351000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-442000000 {
+			opp-hz = /bits/ 64 <442000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-546000000 {
+			opp-hz = /bits/ 64 <546000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-650000000 {
+			opp-hz = /bits/ 64 <650000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-806000000 {
+			opp-hz = /bits/ 64 <806000000>;
+			opp-microvolt = <656250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-949000000 {
+			opp-hz = /bits/ 64 <949000000>;
+			opp-microvolt = <681250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1053000000 {
+			opp-hz = /bits/ 64 <1053000000>;
+			opp-microvolt = <706250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1157000000 {
+			opp-hz = /bits/ 64 <1157000000>;
+			opp-microvolt = <737500>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1300000000 {
+			opp-hz = /bits/ 64 <1300000000>;
+			opp-microvolt = <781250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1456000000 {
+			opp-hz = /bits/ 64 <1456000000>;
+			opp-microvolt = <825000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1586000000 {
+			opp-hz = /bits/ 64 <1586000000>;
+			opp-microvolt = <875000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1742000000 {
+			opp-hz = /bits/ 64 <1742000000>;
+			opp-microvolt = <937500>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1846000000 {
+			opp-hz = /bits/ 64 <1846000000>;
+			opp-microvolt = <981250>;
+			clock-latency-ns = <500000>;
+		};
+	};
+
+	cpucl1_opp_table: opp-table-1 {
+		compatible = "operating-points-v2";
+		opp-shared;
+
+		opp-130000000 {
+			opp-hz = /bits/ 64 <130000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-182000000 {
+			opp-hz = /bits/ 64 <182000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-247000000 {
+			opp-hz = /bits/ 64 <247000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-351000000 {
+			opp-hz = /bits/ 64 <351000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-442000000 {
+			opp-hz = /bits/ 64 <442000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-546000000 {
+			opp-hz = /bits/ 64 <546000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-650000000 {
+			opp-hz = /bits/ 64 <650000000>;
+			opp-microvolt = <625000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-806000000 {
+			opp-hz = /bits/ 64 <806000000>;
+			opp-microvolt = <656250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-949000000 {
+			opp-hz = /bits/ 64 <949000000>;
+			opp-microvolt = <681250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1053000000 {
+			opp-hz = /bits/ 64 <1053000000>;
+			opp-microvolt = <706250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1157000000 {
+			opp-hz = /bits/ 64 <1157000000>;
+			opp-microvolt = <737500>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1300000000 {
+			opp-hz = /bits/ 64 <1300000000>;
+			opp-microvolt = <781250>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1456000000 {
+			opp-hz = /bits/ 64 <1456000000>;
+			opp-microvolt = <825000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1586000000 {
+			opp-hz = /bits/ 64 <1586000000>;
+			opp-microvolt = <875000>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1742000000 {
+			opp-hz = /bits/ 64 <1742000000>;
+			opp-microvolt = <937500>;
+			clock-latency-ns = <500000>;
+		};
+
+		opp-1846000000 {
+			opp-hz = /bits/ 64 <1846000000>;
+			opp-microvolt = <981250>;
+			clock-latency-ns = <500000>;
 		};
 	};
 

-- 
2.51.0