Re: [PATCH v4 5/5] media: qcom: jpeg: Add Qualcomm JPEG V4L2 encoder
From: Vladimir Zapolskiy
Date: Wed Jul 08 2026 - 06:36:40 EST
Hi Gjorgji.
On 7/8/26 12:32, Gjorgji Rosikopulos (Consultant) wrote:
Hi Vlad,
On 7/8/2026 11:47 AM, Vladimir Zapolskiy wrote:
Hi Gjorgji.I agree but there should be an API for icc voting which Jpeg need to use,
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.
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.>
Sure, but I believe it's quite clear that any software implementation
should be discussed only when the hardware description is fixed.
There is SM8250 CAMSS device, which serves as a hierarchical parent (orI agree the device tree is best to represent real hw topology. >
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.
Well, it's not just the best, it's the only possible way.
Copying of the same identical information about clocks, interconnectsHere also i tend to agree.>
and power domains from the hierarchical parent device to children devices
is not needed, and practically it only lowers signal-to-noise ratio.
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.
To move forward there should be a clear answer to a simple question,
does Qualcomm JPEG encoder IP belong to CAMSS group of devices or not?
If no, then JPEG encoder device tree node shall be located outside of
CAMSS device tree node, all resources needed for JPEG encoder device
operation get their descrition in this stand-alone device tree node.
If yes, then JPEG encoder device tree node is a child of CAMSS "bus"
device tree node, and only resources specific to JPEG encoder device
are described in its device tree node, because other resources are
already described in the parent device tree node.
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.
First of all it should get a reviewed dt binding documentation, let's
do it, and a software implementation will follow the agreement.
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? :-)
Here device tree bindings maintainers should share their view, if
hardware properties should be literally repeated in each child device
tree node and their parent device node (star topology, N copies one
for each child), or not (tree topology, 1 copy in parent's node),
this is a generic question.
--
Best wishes,
Vladimir