Re: [PATCH] arm64: dts: exynos850: Add SRAM node

["Alexey Klimov" <alexey.klimov@linaro.org>]

On Tue Apr 14, 2026 at 10:08 AM BST, Krzysztof Kozlowski wrote:
> On 14/04/2026 11:00, Alexey Klimov wrote:
>> On Mon Apr 13, 2026 at 4:23 PM BST, Krzysztof Kozlowski wrote:
>>> On 13/04/2026 16:52, Alexey Klimov 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 | 8 ++++++++
>>>>  1 file changed, 8 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
>>>> index cb55015c8dce..cf4a6168846c 100644
>>>> --- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
>>>> +++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
>>>> @@ -910,6 +910,14 @@ spi_2: spi@11d20000 {
>>>>  			};
>>>>  		};
>>>>  	};
>>>> +
>>>> +	apm_sram: sram@2039000 {
>>>> +		compatible = "mmio-sram";
>>>> +		reg = <0x0 0x2039000 0x40000>;
>>>> +		#address-cells = <1>;
>>>> +		#size-cells = <1>;
>>>> +		ranges = <0x0 0x0 0x2039000 0x40000>;
>>>
>>> You miss here children.
>> 
>> Thank you! I guess I should convert it to smth like this:
>> 
>> apm_sram: sram@2039000 {
>> 		compatible = "mmio-sram";
>> 		reg = <0x0 0x2039000 0x40000>;
>> 		ranges = <0x0 0x0 0x2039000 0x40000>;
>> 		#address-cells = <1>;
>> 		#size-cells = <1>;
>> 
>> 		acpm_sram_region: sram-section@0 {
>> 			reg = <0x0 0x40000>;
>
> This covers entire block, so feels pointless. Maybe requirement of
> children should be dropped. What's the point of having children? Why
> does the driver need them?

Thinking further about this. I was looking at the schema file and
different commits and it the right approach could be:

- add separate compatible for mmio-sram region for this case. Similar
to scmi and scpi, i'd say it should be "exynos,acpm-sram" or
"samsung,acpm-sram";

- update schema sram.yaml to exclude requirement for having child nodes
and properties like ranges, address and size cells
Similar like in commit, for instance, git show d0fe6491ddd22
(or git show 2d4a22e79a5fd).

- then this addition becomes:

	apm_sram: sram@2039000 {
		compatible = "exynos,acpm-sram";
		reg = <0x0 0x2039000 0x40000>;
	};

and will be consumed as a whole region (also as Tudor mentioned in the
other email).
And then we should update gs101 dts as well. Thoughts?

I honestly don't know why be default schema requires child nodes unless
it is specifically excluded. Could be a good question to Rob?
Or maybe we should really drop a requirement for having children from
schema.


>> And then later reference shmem = &acpm_sram_region from acpm node.
>> 
>>> Also, 'ranges' should be after 'reg'.
>> 
>> Thanks, will fix this.
>> 
>> FWIW this commit is a copy of commit 48e7821b26904
>> https://lore.kernel.org/r/20250207-gs101-acpm-dt-v4-1-230ba8663a2d@linaro.org
>
>
> Huh, we should fix that one as well.

Best regardss,
Alexey