linux-kernel - Re: [PATCH] media: qcom: camss: Enable setting the rate to camnoc_rt

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Message-ID: <ab43c5c9-edc5-459e-8ef7-2aa8bec559c0@oss.qualcomm.com>
Date: Thu, 16 Oct 2025 13:53:53 -0700
From: Vijay Kumar Tumati <vijay.tumati@....qualcomm.com>
To: Bryan O'Donoghue <bod@...nel.org>,
        Loic Poulain <loic.poulain@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Hangxiang Ma <hangxiang.ma@....qualcomm.com>,
        Robert Foss
 <rfoss@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Todor Tomov <todor.too@...il.com>,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>, linux-i2c@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH] media: qcom: camss: Enable setting the rate to
 camnoc_rt_axi clock


On 10/16/2025 8:31 AM, Bryan O'Donoghue wrote:
> On 16/10/2025 13:22, Loic Poulain wrote:
>>> I'm - perhaps naively - assuming this clock really is required ... and
>>> that both will be needed concurrently.
>> AFAIU, the NRT clock is not in use for the capture part, and only
>> required for the offline processing engine (IPE, OPE), which will
>> likely be described as a separated node.
>
> Maybe yeah though we already have bindings.
>
> @Hangxiang I thought we had discussed this clock was required for your 
> setup.
>
> Can you confirm with a test and then
>
> 1. Repost with my RB - I assume you included this on purpose
> 2. Respond that you can live without it.
>
> ---
> bod
>
@Bryan and others, sorry, I am just trying to understand the exact ask 
here. Just to add a bit more detail here, On certain architectures, 
there is one CAMNOC module that connects all of the camera modules (RT 
and NRT) to MMNOC. In these, there is one 'camnoc_axi' clock that needs 
to be enabled for it's operation. However, on the newer architectures, 
this single CAMNOC is split into two, one for RT modules (TFEs and IFE 
Lites) and the other for NRT (IPE and OFE). So, on a given architecture, 
we either require 'camnoc_axi' or 'camnoc_rt_axi' for RT operation, not 
both. And yes, one of them is a must. As you know, adding the support 
for the newer clock in "vfe_match_clock_names" will only enable the 
newer chip sets to define this in it's resource information and set the 
rate to it based on the pixel clock. In kaanapali vfe resources, we do 
not give the 'camnoc_axi_clk'. Hopefully we are all on the same page 
now, is it the suggestion to use 'camnoc_axi_clk' name for 
CAM_CC_CAMNOC_RT_AXI_CLK ? We thought it would be clearer to use the 
name the matches the exact clock. Please advise and thank you.