linux-kernel - Re: [PATCH 3/7] arm64: dts: qcom: ipq6018: Add the IMEM node

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Message-ID: <0a646e08-8007-4bc0-9324-fa1d40b90d20@oss.qualcomm.com>
Date: Wed, 2 Jul 2025 15:00:43 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] arm64: dts: qcom: ipq6018: Add the IMEM node

On 7/2/25 12:50 PM, Krzysztof Kozlowski wrote:
> On 02/07/2025 12:17, Kathiravan Thirumoorthy wrote:
>> Add the IMEM node to the device tree to extract debugging information
>> like system restart reason, which is populated via IMEM. Define the
>> IMEM region to enable this functionality.
>>
>> As described, overall IMEM region is approximately 32KB but only initial
>> 4KB is accessible by all masters in the SoC.
>>
>> Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
>> ---
>>  arch/arm64/boot/dts/qcom/ipq6018.dtsi | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/qcom/ipq6018.dtsi b/arch/arm64/boot/dts/qcom/ipq6018.dtsi
>> index bfe59b0208415902c69fd0c0c7565d97997d4207..7eca5ba416c2ef5ef1c4e0eb4f58f1ca94fc92f0 100644
>> --- a/arch/arm64/boot/dts/qcom/ipq6018.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/ipq6018.dtsi
>> @@ -659,6 +659,15 @@ qpic_nand: nand-controller@...0000 {
>>  			status = "disabled";
>>  		};
>>  
>> +		sram@...0000 {
>> +			compatible = "qcom,ipq6018-imem", "syscon", "simple-mfd";
> 
> No, this is not a simple MFD. Where are any children if this is a MFD?

IMEM is just a block of SRAM shared across cores on the platform.
It's present on all Qualcomm platforms and usually stores cookies
such as reboot reason.

A user would be welcome, but I'm not opposed to a lone description
either, at it still shrinks the undescribed-reg-space-hole

Konrad