linux-kernel - Re: [PATCH v2 1/4] dt-bindings: soc: qcom: Add qcom,kaanapali-imem compatible

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Message-ID: <879adf4f-492e-4107-b034-dbd3a4866f40@oss.qualcomm.com>
Date: Thu, 23 Oct 2025 10:54:28 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Bjorn Andersson <andersson@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Jingyi Wang <jingyi.wang@....qualcomm.com>, Rob Herring
 <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Robert Marko <robimarko@...il.com>,
        Das Srinagesh <quic_gurus@...cinc.com>, aiqun.yu@....qualcomm.com,
        tingwei.zhang@....qualcomm.com, trilok.soni@....qualcomm.com,
        yijie.yang@....qualcomm.com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eugen Hristev <eugen.hristev@...aro.org>
Subject: Re: [PATCH v2 1/4] dt-bindings: soc: qcom: Add qcom,kaanapali-imem
 compatible

On 10/23/25 12:42 AM, Bjorn Andersson wrote:
> On Wed, Oct 22, 2025 at 12:34:58PM +0300, Dmitry Baryshkov wrote:
>> On Wed, Oct 22, 2025 at 05:05:30PM +0800, Jingyi Wang wrote:
>>>
>>>
>>> On 10/22/2025 4:49 PM, Dmitry Baryshkov wrote:
>>>> On Wed, Oct 22, 2025 at 12:28:41AM -0700, Jingyi Wang wrote:
>>>>> Document qcom,kaanapali-imem compatible.
>>>>>
>>>>> Reviewed-by: Eugen Hristev <eugen.hristev@...aro.org>
>>>>> Signed-off-by: Jingyi Wang <jingyi.wang@....qualcomm.com>
>>>>> ---
>>>>>  Documentation/devicetree/bindings/sram/qcom,imem.yaml | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/sram/qcom,imem.yaml b/Documentation/devicetree/bindings/sram/qcom,imem.yaml
>>>>> index 6a627c57ae2f..1e29a8ff287f 100644
>>>>> --- a/Documentation/devicetree/bindings/sram/qcom,imem.yaml
>>>>> +++ b/Documentation/devicetree/bindings/sram/qcom,imem.yaml
>>>>> @@ -19,6 +19,7 @@ properties:
>>>>>        - enum:
>>>>>            - qcom,apq8064-imem
>>>>>            - qcom,ipq5424-imem
>>>>> +          - qcom,kaanapali-imem
>>>>
>>>> Can you use mmio-sram instead?
>>>>
>>>
>>> Here is the node: 
>>>
>>> 		sram@...80000 {
>>> 			compatible = "qcom,kaanapali-imem", "syscon", "simple-mfd";
>>> 			reg = <0x0 0x14680000 0x0 0x1000>;
>>> 			ranges = <0 0 0x14680000 0x1000>;
>>>
>>> 			#address-cells = <1>;
>>> 			#size-cells = <1>;
>>>
>>> 			pil-reloc@94c {
>>> 				compatible = "qcom,pil-reloc-info";
>>> 				reg = <0x94c 0xc8>;
>>> 			};
>>> 		};
>>>
>>> other qualcomm are also using imem, could you please give more details on why
>>> we should use mmio-sram here?
>>
>> https://lore.kernel.org/linux-arm-msm/e4c5ecc3-fd97-4b13-a057-bb1a3b7f9207@kernel.org/
>>
> 
> I considered exactly this when I wrote the binding back then...
> 
> But the binding defines mmio-sram as "Simple IO memory regions to be
> managed by the genalloc API." and the Linux sram driver follows that and
> registers a gen_pool across the sram memory region.
> 
> I believe IMEM is SRAM (it's at least not registers), but its memory
> layout is fixed, so it's not a pool in any form.

I tried to get answers for this internally, but no dice.. It's fair
to assume that's what it is though, I think..

We can probably change the compatible and restart my old IPA-IMEM
series which touched upon that while at it:

code+bindings:
https://lore.kernel.org/lkml/20250527-topic-ipa_imem-v2-0-6d1aad91b841@oss.qualcomm.com/

(incl. discussion with Krzysztof about mmio-sram)

dt:
https://lore.kernel.org/linux-arm-msm/20250523-topic-ipa_mem_dts-v1-0-f7aa94fac1ab@oss.qualcomm.com/

I seem to even have the relevant bindings patches on my computer:

https://github.com/quic-kdybcio/linux/commits/topic/imem_sram/

Konrad