Re: [PATCH v4 5/5] media: qcom: jpeg: Add Qualcomm JPEG V4L2 encoder

["Gjorgji Rosikopulos (Consultant)" <gjorgji.rosikopulos@oss.qualcomm.com>]

Hi Vlad,

On 7/8/2026 11:47 AM, Vladimir Zapolskiy wrote:
> Hi Gjorgji.
> 
> On 7/7/26 16:24, Gjorgji Rosikopulos (Consultant) wrote:
>> Hi Vlad,
>>
>> On 7/6/2026 10:46 AM, Vladimir Zapolskiy wrote:
>> <snip>
>>>>
>>>> +            interconnects = <&gem_noc MASTER_AMPSS_M0
>>>> QCOM_ICC_TAG_ACTIVE_ONLY
>>>> +                             &config_noc SLAVE_CAMERA_CFG
>>>> QCOM_ICC_TAG_ACTIVE_ONLY>,
>>>> +                            <&mmss_noc MASTER_CAMNOC_HF
>>>> QCOM_ICC_TAG_ALWAYS
>>>> +                             &mc_virt SLAVE_EBI_CH0
>>>> QCOM_ICC_TAG_ALWAYS>,
>>>> +                            <&mmss_noc MASTER_CAMNOC_SF
>>>> QCOM_ICC_TAG_ALWAYS
>>>> +                             &mc_virt SLAVE_EBI_CH0
>>>> QCOM_ICC_TAG_ALWAYS>;
>>>> +            interconnect-names = "cpu-cfg",
>>>> +                                 "hf-mnoc",
>>>> +                                 "sf-mnoc";
>>>
>>> This is the topic, which may raise a disagreement, but I'll repeat my
>>> position about the need to remove all "CAMSS bus" specific resources from
>>> the device node, they are found and should be allocated on parent's side.
>>
>> The interconnect has functionality to handle bw requests from different
>> clients.
>>
>> Yes the best will be to have camss interconnect, so jpeg and other hw's
>> to vote
>>
>> on that (actually it is possible in icc framework) but what is the
>> benefit of moving
>>
>> those to camss? Is it not better to create camss icc. I understand
>> you want them to be on parent side. But how to vote on bw? Most of the
>> time it
> 
> Let's concentrate on hardware bindings description, no APIs, votes etc.
> at this point of discussion.
I agree but there should be an API for icc voting which Jpeg need to use,
currently it is fixed to some values, but voting need to become dynamic
at some point of time, because it depends on runtime parameters, resolution
format etc.> 
> There is SM8250 CAMSS device, which serves as a hierarchical parent (or
> could be considered as a "bus" device) to this new JPEG encoder device
> and probably to a number of future IPs under CAMSS. All CAMSS sub-devices
> get hardware descriptions as children device tree nodes of CAMSS parent
> device tree node naturally.
I agree the device tree is best to represent real hw topology. > 
> Copying of the same identical information about clocks, interconnects
> and power domains from the hierarchical parent device to children devices
> is not needed, and practically it only lowers signal-to-noise ratio.
Here also i tend to agree.> 
> Since information about the actual defect in hardware description is
> reported, the problem can and should be avoided, the handling of a better
> hardware description and dealing with any kind of complexity will be done
> in the CAMSS and/or CAMSS children drivers.
> 
> If you need to get a bit more formal point of view on the matter, I'd
> prefer to see descriptions of hardware properties organised in a tree
> topology rather than in the originally proposed star topology. By doing
> it the system complexity is reduced from N to 1.

Maybe I'm missing the whole picture of your proposal, but I want to add my
point of view on this matter.

The JPEG encoder HW block has no dependency on the other processing HW
blocks in the camera subsystem

It shares resources like camnoc, clocks, GDSC, etc.,
but does not share anything with the other HW processing blocks. For me, 
the JPEG driver should not have SW architectural dependencies on CAMSS.

The shared resources within the camera subsystem are reference-counted,
the only exception is clock rates, which are set based on the last set_rate
call — but I think that could be handled by migrating the clocks to be
represented as an icc-clk provider, to keep the higher clock and maintain
the needed policy.

What I think would be best (just a proposal) is to introduce a new camera-icc
provider that handles all these resources — camera operates on bandwidth
anyway, and rate calculations should be done in icc, since the  infrastructure
for that already exists in the icc framework. But I think this has already been
discussed with Atanas, so maybe there's no need to go over it again.

I'm not sure how to move forward with the JPEG encoder changes.

I see two different proposals:
1. Independent sub-nodes (Bryan's direction) — I honestly like this one more.
2. CAMSS handling the resources currently managed by the other frameworks.
There are good arguments for this too.

Bryan, as maintainer, can you say which direction to post next? :-)

Apart from t


Regards,
~Gjorgji