linux-kernel - Re: [PATCH RFC 2/6] arm64: dts: qcom: ipq5424: Add the IMEM node

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Message-ID: <4a737b56-9d26-4f81-a7e3-8644ed787373@oss.qualcomm.com>
Date: Fri, 11 Apr 2025 14:47:32 +0530
From: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....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>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org
Subject: Re: [PATCH RFC 2/6] arm64: dts: qcom: ipq5424: Add the IMEM node


On 4/11/2025 2:33 PM, Konrad Dybcio wrote:
> On 4/11/25 7:01 AM, Kathiravan Thirumoorthy wrote:
>> On 4/10/2025 12:11 AM, Konrad Dybcio wrote:
>>> On 4/8/25 10:49 AM, 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. Corresponding DTS and driver
>>>> changes will be added incrementally.
>>>>
>>>> Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
>>>> ---
>>>>    arch/arm64/boot/dts/qcom/ipq5424.dtsi | 9 +++++++++
>>>>    1 file changed, 9 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/qcom/ipq5424.dtsi b/arch/arm64/boot/dts/qcom/ipq5424.dtsi
>>>> index 5d6ed2172b1bb0a57c593f121f387ec917f42419..a772736f314f46d11c473160c522af4edeb900b7 100644
>>>> --- a/arch/arm64/boot/dts/qcom/ipq5424.dtsi
>>>> +++ b/arch/arm64/boot/dts/qcom/ipq5424.dtsi
>>>> @@ -486,6 +486,15 @@ ssphy_0: phy@...00 {
>>>>                status = "disabled";
>>>>            };
>>>>    +        sram@...0000 {
>>>> +            compatible = "qcom,ipq5424-imem", "syscon", "simple-mfd";
>>>> +            reg = <0 0x08600000 0 0x1000>;
>>>> +            ranges = <0 0 0x08600000 0x1000>;
>>> It looks like this should be a little longer
>>
>> Yes. It is 112KB. But only first 4KB is accessible by all masters in the system, remaining regions are access protected by TZ. I shall mention this in the commit message in the next version.
> I think we should describe the full length of it - it's only if we
> add a subnode that we actually access it


Sure got it.  I will describe the full length in next revision. In that 
case, it would be the driver's responsibility not to go beyond the 
initial 4K.


>
> Konrad