linux-kernel - Re: [PATCH 1/3] dt-bindings: interconnect: add clocks property to enable QoS on sa8775p

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Message-ID: <26e5309e-3705-4d70-a2e7-3f0e9344816b@kernel.org>
Date: Fri, 29 Aug 2025 00:59:49 +0300
From: Georgi Djakov <djakov@...nel.org>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Odelu Kukatla <odelu.kukatla@....qualcomm.com>, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>
Cc: Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
 linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Mike Tipton <mike.tipton@....qualcomm.com>
Subject: Re: [PATCH 1/3] dt-bindings: interconnect: add clocks property to
 enable QoS on sa8775p

On 8/28/25 9:20 PM, Krzysztof Kozlowski wrote:
> On 28/08/2025 20:16, Odelu Kukatla wrote:
>>
>>>> QoS configuration is essential for managing latency and bandwidth across
>>>> subsystems such as CPU, GPU, and multimedia engines. Without it, the
>>>> system may experience performance degradation, especially under
>>>
>>> So how was it working for the last 2 years?
>>>
>> The system may function normally without this feature. However, enabling
> 
> 
> Huh? So you agree but keep continuing the discussion?
> 
> I don't understand what we are discussing in such case, but just to
> close the topic from my side and be explicit: based on above you cannot
> break the ABI.

To be even more specific, if we already have some DT binding without any
clocks and reg properties, we can't just suddenly change them from now
on to be "required". But they can still be "optional" and this will not
break the ABI, right? The old DT is still valid and the QoS will be
active when the new properties are present and this is handled properly
by the driver.

BR,
Georgi

> 
>> QoS helps optimize latency and bandwidth across subsystems like CPU,
>> GPU, and multimedia engines, which becomes important in high-throughput
>> scenarios.
> 
> No one discussed that.
> 
> 
> Best regards,
> Krzysztof