[PATCH v3 0/2] Exynos850 ACPM SRAM devicetree node

[PATCH v3 0/2] Exynos850 ACPM SRAM devicetree node

[Alexey Klimov]

Hi all,

this is a small series that adds sram node required for ACPM communication.
Bindings update adds new compatible "samsung,exynos850-acpm-sram" there and
excludes it from having child nodes and not required properties.
The node becomes a simple one:

apm_sram: sram@2039000 {
	compatible = "samsung,exynos850-acpm-sram";
	reg = <0x2039000 0x40000>;
}

The ACPM driver will just continue to parse shmem phandle, so
as far as I can see no updates there are required.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
Changes in v3:
- sram node moved to the beginning of SoC section in DT change,
  reg property updated to match section requirement address-cells=1;
- updated trailers;
- Link to v2: https://lore.kernel.org/r/20260723-exynos850_sram-v2-0-c94968e52f42@linaro.org

Changes in v2:
- small update of the initial commit message
  "Add SRAM node" -> "Add acpm SRAM node"
- new commit, updates dt bindings to exclude sram node to have child nodes
  and related properties, this adds new compatible
  samsung,exynos850-acpm-sram
- Link to v1: https://lore.kernel.org/r/20260413-exynos850_sram-v1-1-7fda5b7fb7d4@linaro.org

---
Alexey Klimov (2):
      dt-bindings: sram: Document samsung,exynos850-acpm-sram
      arm64: dts: exynos850: Add acpm SRAM node

 Documentation/devicetree/bindings/sram/sram.yaml | 2 ++
 arch/arm64/boot/dts/exynos/exynos850.dtsi        | 5 +++++
 2 files changed, 7 insertions(+)
---
base-commit: b4515cf4156356e8f4fe6e0fdc17f59adab9772f
change-id: 20260413-exynos850_sram-ca1200b99e82

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

[PATCH v3 1/2] dt-bindings: sram: Document samsung,exynos850-acpm-sram

[Alexey Klimov]

Document "samsung,exynos850-acpm-sram" which represents an SRAM region used
for ACPM communication on Samsung-based SoCs.

The SRAM is consumed as a whole, is not split up using child nodes and
properties related to this are not required.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 Documentation/devicetree/bindings/sram/sram.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/sram/sram.yaml b/Documentation/devicetree/bindings/sram/sram.yaml
index b83fc6831947..b9c4d4f3199b 100644
--- a/Documentation/devicetree/bindings/sram/sram.yaml
+++ b/Documentation/devicetree/bindings/sram/sram.yaml
@@ -43,6 +43,7 @@ properties:
         - qcom,rpm-msg-ram
         - qcom,shikra-imem
         - rockchip,rk3288-pmu-sram
+        - samsung,exynos850-acpm-sram
 
   reg:
     maxItems: 1
@@ -159,6 +160,7 @@ if:
           enum:
             - qcom,rpm-msg-ram
             - rockchip,rk3288-pmu-sram
+            - samsung,exynos850-acpm-sram
 then:
   required:
     - "#address-cells"

-- 
2.51.0

[PATCH v3 2/2] arm64: dts: exynos850: Add acpm SRAM node

[Alexey Klimov]

SRAM is used by the ACPM protocol to retrieve the ACPM channels
information and configuration data. Add the SRAM node.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 arch/arm64/boot/dts/exynos/exynos850.dtsi | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
index 3881f573ec08..0b614caa411c 100644
--- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
+++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
@@ -163,6 +163,11 @@ soc: soc@0 {
 		#size-cells = <1>;
 		ranges = <0x0 0x0 0x0 0x20000000>;
 
+		apm_sram: sram@2039000 {
+			compatible = "samsung,exynos850-acpm-sram";
+			reg = <0x2039000 0x40000>;
+		};
+
 		chipid@10000000 {
 			compatible = "samsung,exynos850-chipid";
 			reg = <0x10000000 0x100>;

-- 
2.51.0

Re: [PATCH v3 0/2] Exynos850 ACPM SRAM devicetree node

[Alexey Klimov]

Hi all,

On Mon Jul 27, 2026 at 2:23 PM BST, Alexey Klimov wrote:
> Hi all,
>
> this is a small series that adds sram node required for ACPM communication.
> Bindings update adds new compatible "samsung,exynos850-acpm-sram" there and
> excludes it from having child nodes and not required properties.

Gentle ping.

What is missing here? Should it be split into two separate coomits?
There are no comments for at least a month.

[..]

> Alexey Klimov (2):
>       dt-bindings: sram: Document samsung,exynos850-acpm-sram
>       arm64: dts: exynos850: Add acpm SRAM node
>
>  Documentation/devicetree/bindings/sram/sram.yaml | 2 ++
>  arch/arm64/boot/dts/exynos/exynos850.dtsi        | 5 +++++
>  2 files changed, 7 insertions(+)
> ---

Thanks,
Alexey

Re: [PATCH v3 2/2] arm64: dts: exynos850: Add acpm SRAM node

[Sam Protsenko]

On Mon, Jul 27, 2026 at 8:23 AM Alexey Klimov <alexey.klimov@linaro.org> wrote:
>
> SRAM is used by the ACPM protocol to retrieve the ACPM channels
> information and configuration data. Add the SRAM node.
>
> Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
> ---
>  arch/arm64/boot/dts/exynos/exynos850.dtsi | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
> index 3881f573ec08..0b614caa411c 100644
> --- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
> +++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
> @@ -163,6 +163,11 @@ soc: soc@0 {
>                 #size-cells = <1>;
>                 ranges = <0x0 0x0 0x0 0x20000000>;
>
> +               apm_sram: sram@2039000 {
> +                       compatible = "samsung,exynos850-acpm-sram";
> +                       reg = <0x2039000 0x40000>;

Why it's 0x40000? I checked the TRM, and it says iRAM APM area is from
0x02039000 to 0x02069000, which is 0x30000 (192 KiB). The downstream
kernel (v4.14) also say the APM SRAM size is 0x30000.

> +               };
> +
>                 chipid@10000000 {
>                         compatible = "samsung,exynos850-chipid";
>                         reg = <0x10000000 0x100>;
>
> --
> 2.51.0
>

Re: [PATCH v3 1/2] dt-bindings: sram: Document samsung,exynos850-acpm-sram

[Alexey Klimov]

On Fri Sep 11, 2026 at 1:42 AM BST, Sam Protsenko wrote:
> On Mon, Jul 27, 2026 at 8:23 AM Alexey Klimov <alexey.klimov@linaro.org> wrote:
>>
>> Document "samsung,exynos850-acpm-sram" which represents an SRAM region used
>> for ACPM communication on Samsung-based SoCs.
>>
>> The SRAM is consumed as a whole, is not split up using child nodes and
>> properties related to this are not required.
>>
>> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
>> Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
>> ---
>>  Documentation/devicetree/bindings/sram/sram.yaml | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/sram/sram.yaml b/Documentation/devicetree/bindings/sram/sram.yaml
>> index b83fc6831947..b9c4d4f3199b 100644
>> --- a/Documentation/devicetree/bindings/sram/sram.yaml
>> +++ b/Documentation/devicetree/bindings/sram/sram.yaml
>> @@ -43,6 +43,7 @@ properties:
>>          - qcom,rpm-msg-ram
>>          - qcom,shikra-imem
>>          - rockchip,rk3288-pmu-sram
>> +        - samsung,exynos850-acpm-sram
>
> Is there a reason we can't just use "mmio-sram" for Exynos850 ACPM
> needs? I can see it's used in the gs101 device tree like this. If
> there is a reason for this, I think it might be a good idea to
> document it in the commit message (probably in both patches).

But isn't it already in this commit message?
"The SRAM is consumed as a whole, is not split up using child nodes and
properties related to this are not required."

Also: https://lore.kernel.org/all/5797be19-8886-45a2-bfce-eb7d5f0df6c2@linaro.org/

Do you want it to be re-phrased smth like this:
"OSPM ACPM should parse the SRAM and discover essential data (e.g. queue
offsets) for establishing ACPM communication. At this point it is not
expected for any software entities apart ACPM to use SRAM so the SRAM is
consumed as a whole, is not split up using child nodes and properties
related to this are not required."

or

"The OSPM/ACPM IPC should parse the SRAM at runtime to find configuration
data (e.g., queue offsets). Because this SRAM region is dedicated
exclusively to ACPM IPC communication and is not shared with other
software entities, it is represented as a monolithic SRAM block without
requiring sub-node partitioning."

?

I hope if there will be other software entities then we will be able to
fix it later.

>Also,
> should "mmio-sram" be added as a backup option (after comma) in your
> [PATCH 2/2]?

Sure, I can add "mmio-sram".
The compatible = "rockchip,rk3288-pmu-sram", "mmio-sram"
and compatible = "qcom,rpm-msg-ram", "mmio-sram" are used in such way.

Best regards,
Alexey

Re: [PATCH v3 2/2] arm64: dts: exynos850: Add acpm SRAM node

[Alexey Klimov]

On Fri Sep 11, 2026 at 1:28 AM BST, Sam Protsenko wrote:
> On Mon, Jul 27, 2026 at 8:23 AM Alexey Klimov <alexey.klimov@linaro.org> wrote:
>>
>> SRAM is used by the ACPM protocol to retrieve the ACPM channels
>> information and configuration data. Add the SRAM node.
>>
>> Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
>> ---
>>  arch/arm64/boot/dts/exynos/exynos850.dtsi | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
>> index 3881f573ec08..0b614caa411c 100644
>> --- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
>> +++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
>> @@ -163,6 +163,11 @@ soc: soc@0 {
>>                 #size-cells = <1>;
>>                 ranges = <0x0 0x0 0x0 0x20000000>;
>>
>> +               apm_sram: sram@2039000 {
>> +                       compatible = "samsung,exynos850-acpm-sram";
>> +                       reg = <0x2039000 0x40000>;
>
> Why it's 0x40000? I checked the TRM, and it says iRAM APM area is from
> 0x02039000 to 0x02069000, which is 0x30000 (192 KiB). The downstream
> kernel (v4.14) also say the APM SRAM size is 0x30000.

Good catch. That's my bad.

Thanks,
Alexey

Re: [PATCH v3 1/2] dt-bindings: sram: Document samsung,exynos850-acpm-sram

[Sam Protsenko]

On Fri, Sep 11, 2026 at 11:20 AM Alexey Klimov <alexey.klimov@linaro.org> wrote:
>
> On Fri Sep 11, 2026 at 1:42 AM BST, Sam Protsenko wrote:
> > On Mon, Jul 27, 2026 at 8:23 AM Alexey Klimov <alexey.klimov@linaro.org> wrote:
> >>
> >> Document "samsung,exynos850-acpm-sram" which represents an SRAM region used
> >> for ACPM communication on Samsung-based SoCs.
> >>
> >> The SRAM is consumed as a whole, is not split up using child nodes and
> >> properties related to this are not required.
> >>
> >> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
> >> Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
> >> ---
> >>  Documentation/devicetree/bindings/sram/sram.yaml | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/sram/sram.yaml b/Documentation/devicetree/bindings/sram/sram.yaml
> >> index b83fc6831947..b9c4d4f3199b 100644
> >> --- a/Documentation/devicetree/bindings/sram/sram.yaml
> >> +++ b/Documentation/devicetree/bindings/sram/sram.yaml
> >> @@ -43,6 +43,7 @@ properties:
> >>          - qcom,rpm-msg-ram
> >>          - qcom,shikra-imem
> >>          - rockchip,rk3288-pmu-sram
> >> +        - samsung,exynos850-acpm-sram
> >
> > Is there a reason we can't just use "mmio-sram" for Exynos850 ACPM
> > needs? I can see it's used in the gs101 device tree like this. If
> > there is a reason for this, I think it might be a good idea to
> > document it in the commit message (probably in both patches).
>
> But isn't it already in this commit message?
> "The SRAM is consumed as a whole, is not split up using child nodes and
> properties related to this are not required."
>
> Also: https://lore.kernel.org/all/5797be19-8886-45a2-bfce-eb7d5f0df6c2@linaro.org/
>
> Do you want it to be re-phrased smth like this:
> "OSPM ACPM should parse the SRAM and discover essential data (e.g. queue
> offsets) for establishing ACPM communication. At this point it is not
> expected for any software entities apart ACPM to use SRAM so the SRAM is
> consumed as a whole, is not split up using child nodes and properties
> related to this are not required."
>
> or
>
> "The OSPM/ACPM IPC should parse the SRAM at runtime to find configuration
> data (e.g., queue offsets). Because this SRAM region is dedicated
> exclusively to ACPM IPC communication and is not shared with other
> software entities, it is represented as a monolithic SRAM block without
> requiring sub-node partitioning."
>
> ?
>

I was thinking about something more like this (in addition to your
existing commit message):

    "mmio-sram compatible can't be used for ACPM purposes because it
requires child nodes to be declared, which are not needed and make no
sense in case of ACPM."

basically to answer this question directly -- at least if I understood
correctly what was discussed with Krzysztof [1]. Other additions you
mentioned might be valuable too. Anyways, that's just a suggestion, I
figured if you're going to submit the next patch series version, might
as well provide more context in the commit message, but no strong
opinion here. Also, feel free to add:

Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>

> I hope if there will be other software entities then we will be able to
> fix it later.
>
> >Also,
> > should "mmio-sram" be added as a backup option (after comma) in your
> > [PATCH 2/2]?
>
> Sure, I can add "mmio-sram".
> The compatible = "rockchip,rk3288-pmu-sram", "mmio-sram"
> and compatible = "qcom,rpm-msg-ram", "mmio-sram" are used in such way.
>

On the second thought (after reading your discussion with Krzysztof
[1]) that probably is not a good idea, kinda defies the point, because
for "mmio-sram" you'll have to provide more stuff in the node, right?
So I think it's better to keep only:

    compatible = "samsung,exynos850-acpm-sram";

in your [PATCH 2/2].

[1] https://lkml.org/lkml/2026/4/14/523

> Best regards,
> Alexey