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Message-ID: <9b1beb38-9ec2-4bdb-97f5-fccf98d3b0c3@linaro.org>
Date:   Wed, 13 Sep 2023 10:12:12 +0100
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Subject: Re: [PATCH 4/9] arm64: dts: qcom: msm8916: Reserve firmware memory
 dynamically
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To:     Konrad Dybcio <konrad.dybcio@linaro.org>,
        Stephan Gerhold <stephan@gerhold.net>,
        Bjorn Andersson <andersson@kernel.org>
Cc:     Andy Gross <agross@kernel.org>, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        Bryan O'Donoghue <bryan.odonoghue@linaro.org>
References: <20230911-msm8916-rmem-v1-0-b7089ec3e3a1@gerhold.net>
 <20230911-msm8916-rmem-v1-4-b7089ec3e3a1@gerhold.net>
 <912f90ee-0816-43ae-bc6f-a9a9a3e33d8a@linaro.org>
From:   Bryan O'Donoghue <bryan.odonoghue@linaro.org>
In-Reply-To: <912f90ee-0816-43ae-bc6f-a9a9a3e33d8a@linaro.org>
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On 13/09/2023 10:06, Konrad Dybcio wrote:
> On 11.09.2023 19:41, Stephan Gerhold wrote:
>> Most of the reserved firmware memory on MSM8916 can be relocated when
>> respecting the required alignment. To avoid having to precompute the
>> reserved memory regions in every board DT, describe the actual
>> requirements (size, alignment, alloc-ranges) using the dynamic reserved
>> memory allocation.
>>
>> This approach has several advantages:
>>
>>   1. We can define "templates" for the reserved memory regions in
>>      msm8916.dtsi and keep only device-specific details in the board DT.
>>      This is useful for the "mpss" region size for example, which varies
>>      from device to device. It is no longer necessary to redefine all
>>      firmware regions to shift their addresses.
>>
>>   2. When some of the functionality (e.g. WCNSS, Modem, Venus) is not
>>      enabled or needed for a device, the reserved memory can stay
>>      disabled, freeing up the unused reservation for Linux.
>>
>>   3. Devices with special requirements for one of the firmware regions
>>      are handled automatically. For example, msm8916-longcheer-l8150
>>      has non-relocatable "wcnss" firmware that must be loaded exactly
>>      at address 0x8b600000. When this is defined as a static region,
>>      the other dynamic allocations automatically adjust to a different
>>      place with suitable alignment.
>>
>> All in all this approach significantly reduces the boilerplate necessary
>> to define the different firmware regions, and makes it easier to enable
>> functionality on the different devices.
>>
>> Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
>> ---
> [...]
> 
>>   
>>   		mpss_mem: mpss@86800000 {
>> +			/*
>> +			 * The memory region for the mpss firmware is generally
>> +			 * relocatable and could be allocated dynamically.
>> +			 * However, many firmware versions tend to fail when
>> +			 * loaded to some special addresses, so it is hard to
>> +			 * define reliable alloc-ranges.
>> +			 *
>> +			 * alignment = <0x0 0x400000>;
>> +			 * alloc-ranges = <0x0 0x86800000 0x0 0x8000000>;
>> +			 */
> Do we know of any devices that this would actually work on?
> 
> Konrad

I have the same question here.

How was this tested ?

---
bod