linux-kernel - Re: [PATCH 1/2] dt-bindings: reserved-memory: document Qualcomm MPSS DSM memory

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Message-ID: <9aa23650-6ae1-3844-7cf3-6812dc023c11@linaro.org>
Date:   Thu, 17 Nov 2022 10:47:48 +0100
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: reserved-memory: document Qualcomm MPSS
 DSM memory

On 16/11/2022 13:17, Krzysztof Kozlowski wrote:
> On 16/11/2022 11:16, Neil Armstrong wrote:
>> This documents the Qualcomm Modem Processing SubSystem DSM shared memory.
> 
> Do not use "This commit/patch".
> https://elixir.bootlin.com/linux/v5.17.1/source/Documentation/process/submitting-patches.rst#L95
> 
>>
>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>> ---
>>   .../reserved-memory/qcom,mpss-dsm-mem.yaml         | 37 ++++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/reserved-memory/qcom,mpss-dsm-mem.yaml b/Documentation/devicetree/bindings/reserved-memory/qcom,mpss-dsm-mem.yaml
>> new file mode 100644
>> index 000000000000..65f37e1356d4
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/reserved-memory/qcom,mpss-dsm-mem.yaml
>> @@ -0,0 +1,37 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: "http://devicetree.org/schemas/reserved-memory/qcom,mpss-dsm-mem.yaml#"
>> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> 
> Drop quotes from above.
> 
> I know that this and few further pieces came from existing files...

Yep sorry, I'll clean it up.

> 
>> +
>> +title: Qualcomm Modem Processing SubSystem DSM Memory
>> +
>> +description: |
>> +  This binding describes the Qualcomm Modem Processing SubSystem DSM, which serves the
> 
> Drop "This binding describes"
> 
>> +  purpose of describing the shared memory region used for MPSS remote processors.
> 
> Entire description seems like not wrapped at 80.
> 
>> +
>> +maintainers:
>> +  - Bjorn Andersson <bjorn.andersson@...aro.org>
> 
> Need to update the address.

Argh

> 
>> +
>> +allOf:
>> +  - $ref: "reserved-memory.yaml"
> 
> Drop quotes.
> 
>> +
>> +properties:
>> +  compatible:
>> +    const: qcom,mpss-dsm-mem
> 
> Why do we need dedicated binding and compatible for it instead of using
> memory-region phandle in the device?

So like rmtfs, this memory zone is shared between APPS and the MPSS subsystem.

Like rmtfs it makes no sense to link it to the MPSS PAS, since it's only a launcher,
it doesn't represent the MPSS subsystem.

In the PAS startup process, the resources are released from APPS once the MPSS subsystem
is running, which is not the case with the MPSS DSM where it must be shared during the whole
lifetime of the system.

Neil

> 
>> +
>> +unevaluatedProperties: false
> 
> 
> Best regards,
> Krzysztof
>