linux-kernel - Re: [PATCH] arm64: dts: qcom: sc7280: Mark FastRPC context banks as dma-coherent

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Message-ID: <045c2ba8-3ac5-4773-ac7b-a6d8625891c8@oss.qualcomm.com>
Date: Wed, 21 May 2025 17:52:45 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Xilin Wu <sophon@...xa.com>
Cc: cros-qcom-dts-watchers@...omium.org,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: sc7280: Mark FastRPC context banks as
 dma-coherent

On 21/05/2025 17:08, Xilin Wu wrote:
> On 2025/5/21 05:34:08, Dmitry Baryshkov wrote:
>> On Wed, Apr 16, 2025 at 06:54:18PM +0800, Xilin Wu wrote:
>>> The FastRPC context banks are DMA-coherent on sc7280 platform. Mark them
>>> as such.
>>>
>>> This allows LLM inferencing on the CDSP using Qualcomm AI Engine Direct
>>> SDK on the qcs6490 platform.
>>>
>>> Signed-off-by: Xilin Wu <sophon@...xa.com>
>>> ---
>>>   arch/arm64/boot/dts/qcom/sc7280.dtsi | 15 +++++++++++++++
>>>   1 file changed, 15 insertions(+)
>>
>> Are context banks coherent on FP5? On Herobrine? Or Nothing Phone?
>>
> 
> Hi,
> 
> This was tested on an upcoming SBC (Radxa Dragon Q6A) with the Qualcomm 
> Linux cdsp firmware. There would be an error in the LLM demo app without 
> this patch.
> 
> I'm honestly not sure about the devices that you mentioned, since I 
> don't have any other sc7280 devices to test.

You have enabled dma-coherency for the several families of devices using 
SC7280, QCM/QCS6490 and SM7350. Some of them might have older firmware, 
etc. We had this issue with SDM845 / RB3 boards.

Bjorn, do we need to revert this patch? See corresponding discussion at 
https://lore.kernel.org/linux-arm-msm/70ffec25-17c9-4424-9d0b-da6560f7160d@quicinc.com

-- 
With best wishes
Dmitry