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Message-ID: <b71982c3-9f28-4586-8528-3a4f5dbc6eae@linaro.org>
Date:   Sat, 9 Dec 2023 15:23:10 +0100
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Subject: Re: [PATCH v7 2/2] irqchip: irq-qcom-mpm: Support passing a slice of
 SRAM as reg space
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To:     Thomas Gleixner <tglx@linutronix.de>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Marc Zyngier <maz@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Shawn Guo <shawn.guo@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>
Cc:     Marijn Suijten <marijn.suijten@somainline.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org,
        Bryan O'Donoghue <bryan.odonoghue@linaro.org>
References: <20230328-topic-msgram_mpm-v7-0-6ee2bfeaac2c@linaro.org>
 <20230328-topic-msgram_mpm-v7-2-6ee2bfeaac2c@linaro.org>
 <87fs0csqu1.ffs@tglx>
From:   Konrad Dybcio <konrad.dybcio@linaro.org>
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On 8.12.2023 15:37, Thomas Gleixner wrote:
> On Mon, Nov 27 2023 at 16:52, Konrad Dybcio wrote:
> 
> The prefix in the subject is wrong. Also please write out register. This
> is not Xitter.
Had a feeling it would be too long, but actually it'd be perfect
72 chars :)

> 
>> The MPM hardware is accessible to us from the ARM CPUs through a shared
> 
> to us? Can you access that hardware? I doubt it.
With a small enough "stick".. but I get your point

> 
> Please use neutral tone as documented in Documentation/process/
> 
>> memory region (RPM MSG RAM) that's also concurrently accessed by other
>> kinds of cores on the system (like modem, ADSP etc.). Modeling this
>> relation in a (somewhat) sane manner in the device tree basically
>> requires us to either present the MPM as a child of said memory region
>> (which makes little sense, as a mapped memory carveout is not a bus),
>> define nodes which bleed their register spaces into one another, or
>> passing their slice of the MSG RAM through some kind of a property.
>>
>> Go with the third option and add a way to map a region passed through
>> the "qcom,rpm-msg-ram" property as our register space.
>>
>> The current way of using 'reg' is preserved for ABI reasons.
> 
> It's not an ABI reason. It's backwards compatibility with old device
> trees, right?
Yes, I thought of something else.

> 
> I'll fix it up for you this time. No need to resend.
Thanks!

Konrad