linux-kernel - Re: [PATCH v7 2/3] arm64: dts: qcom: qcs615: add venus node to devicetree

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Message-ID: <b9752b9f-54d8-4ae0-916a-76149abcce69@oss.qualcomm.com>
Date: Wed, 4 Jun 2025 16:19:18 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Renjiang Han <quic_renjiang@...cinc.com>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        Dikshita Agarwal <quic_dikshita@...cinc.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.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-media@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v7 2/3] arm64: dts: qcom: qcs615: add venus node to
 devicetree

On 6/4/25 3:41 PM, Dmitry Baryshkov wrote:
> On Wed, Jun 04, 2025 at 03:24:25PM +0200, Konrad Dybcio wrote:
>> On 6/4/25 2:05 PM, Renjiang Han wrote:
>>>
>>> On 6/3/2025 9:21 PM, Dmitry Baryshkov wrote:
>>>> On Thu, May 29, 2025 at 10:29:46AM +0800, Renjiang Han wrote:
>>>>> On 5/28/2025 7:04 PM, Dmitry Baryshkov wrote:
>>>>>> On Wed, May 28, 2025 at 05:13:06PM +0800, Renjiang Han wrote:
>>>>>>> On 5/27/2025 9:57 PM, Konrad Dybcio wrote:
>>>>>>>> On 5/27/25 5:32 AM, Renjiang Han wrote:
>>>>>>>>> Add the venus node to the devicetree for the qcs615 platform to enable
>>>>>>>>> video functionality. The qcs615 platform currently lacks video
>>>>>>>>> functionality due to the absence of the venus node. Fallback to sc7180 due
>>>>>>>>> to the same video core.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Renjiang Han <quic_renjiang@...cinc.com>
>>>>>>>>> ---
>>>>>>>> [...]
>>>>>>>>
>>>>>>>>> +            interconnect-names = "video-mem",
>>>>>>>>> +                         "cpu-cfg";
>>>>>>>>> +
>>>>>>>>> +            iommus = <&apps_smmu 0xe40 0x20>;
>>>>>>>> fwiw docs mention 0xe60 0x20 (which result in the exact same resulting sid)
>>>>>>> OK. Will update it with next version.
>>>>>> How would you update this?
>>>>> Thanks for your comments. I'll update it like this.
>>>>> iommus = <&apps_smmu 0xe60 0x20>;
>>>>>
>>>>> This 0xe40 SID was based on a previous project. However, after rechecking
>>>>> the documentation yesterday and confirming with colleagues, the correct
>>>>> SID value should be 0xe60. I’ve also validated it on local device, it
>>>>> works as expected. The reason 0xe40 seemed to work earlier is due to the
>>>>> mask value being 0x20, which causes the effective SID derived from 0xe40
>>>>> to be the same as 0xe60.
>>>> Using 0xe60 would be counterintuitive, as we have a non-zero masked bits
>>>> in the base value. It should be either <0xe60 0x0> or <0xe40 0x20>.
>>>
>>> Hi Dmitry
>>>
>>> Thank you for your comment.
>>>
>>> I’ve followed up on this sid with a colleague from the kernel team,
>>> and based on our discussion, it seems that the sid in this case should
>>> be the result sid. The actual sid is 0xe60, and with a mask of 0x20,
>>> the resulting sid would be 0xe40. Therefore, it should be <0xe40 0x20>.
>>>
>>> @Konrad, I’d appreciate any thoughts or suggestions you might have on it.
>>
>> What our docs describe as 'result sid' is literally 'base ~& mask', so if
>> we used that, setting the mask would be useless..
>>
>> Now, some old NHLOS builds are known to cause issues if the values aren't
>> exactly what they expect (some whitelisting must be going on there).
>>
>> I don't think this should be an issue on this platform, but let's just
>> use 0xe60 0x20 here to reflect the real values
> 
> Isn't 0xe40 also 'real'?

0xe60 and 0xe40 (unmasked) are two separate streams

Konrad>