From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B364E20322; Sun, 24 Aug 2025 09:08:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756026500; cv=none; b=kvXJgiWoXnGhGpttLGp3ccB1iyXZ7T46KUOAc8st+SfQRKpYDUEJZuZ9QKAGvfHK+Ri/lO8ICpbgDe32diqKoudc310by1uqoYK6Nnk6l+0FT9Bunun1fFlIV7WN+yd+6vOfFAXYKz3XHhMERZcrE6aCOpQ9yjgqeKrqCjOp8WY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756026500; c=relaxed/simple; bh=Yg1Y0LWbqbOqNwBgnXz+CRC+dctwOX6xg8qtYYFm5J4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tziMNDhg6HDtMPMOW5l4K3JyrFUHB7lY6pjJiCGz+HmQpBWaHInkKN5YuVCrs9OhC/eo2/DULVCKVTcmWmZm6ATXjhg6mhZnlDpyhPISWtDsUVJ+D7pgTz1e3f+El9brllZQPduPFKUZN0PsnUd2uVMslScU0Dy8A6nQRY/KB8w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MgQqIIEt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MgQqIIEt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DFFB2C4CEEB; Sun, 24 Aug 2025 09:08:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756026499; bh=Yg1Y0LWbqbOqNwBgnXz+CRC+dctwOX6xg8qtYYFm5J4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=MgQqIIEt1wGaCYel8cG5qPcOMR83GKAVFur1sZ8/lqIO2J6G4zDD0Ft2DuNGFNpUq +6e9/P4w7wKQXRJvqhpAm6bpvEWSc/YNEWAgrcJ8sYDxvEdT4ljpkmTWr8pmcRCQE+ CHBxDOu20v4r2Po9Z33nhSnAS8j0sAsZQqCLIN2pMoWQOOLLz70wuFHlQFN0TpNpK6 tSfF0stPcrUMMnDC2/C6sbu6HZeZWM4XOflD6qhNXHIQCn8gHGqVSBonr1rr17iolT 2sI1LyrW4EoR2OzXfNbutZO7SHWTDgExWdCivpJY3XSMGIEgX0CxIg8gqLuRM0UzEb HOQwJRdOlHSsQ== Message-ID: <00f50d92-e4ea-4805-b771-147fa5f5ebe4@kernel.org> Date: Sun, 24 Aug 2025 11:08:14 +0200 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] dt-bindings: interconnect: add clocks property to enable QoS on sa8775p To: Odelu Kukatla , Georgi Djakov , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio Cc: Raviteja Laggyshetty , Dmitry Baryshkov , Bartosz Golaszewski , linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Mike Tipton References: <20250808140300.14784-1-odelu.kukatla@oss.qualcomm.com> <20250808140300.14784-2-odelu.kukatla@oss.qualcomm.com> <90b51e31-3217-4483-bb5b-ec328665a723@kernel.org> <28b97952-1b67-411f-a7fb-ddd558739839@oss.qualcomm.com> <7d3e5cf7-4167-4005-ba4b-c1915c254705@oss.qualcomm.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 20/08/2025 10:51, Odelu Kukatla wrote: > > > On 8/13/2025 11:32 AM, Krzysztof Kozlowski wrote: >> On 13/08/2025 07:55, Odelu Kukatla wrote: >>> >>> >>> On 8/12/2025 3:47 PM, Krzysztof Kozlowski wrote: >>>> On 08/08/2025 16:02, Odelu Kukatla wrote: >>>>> Add reg and clocks properties to enable the clocks required >>>>> for accessing QoS configuration. >>>> >>>> >>>> Nothing here explains why EXISTING hardware is being changed. I also >>>> remember big discussions and big confusing patches regarding sa8775p >>>> (its rename, dropping/changing all providers), and this patch feels like >>>> pieces of it without proper justification. >>>> >>> Thanks for the review. >>> I have added description in cover letter, i will add here as well in next revision.> And this is hidden ABI break, no justification, no mentioning either. >>>> Again we are discussing basics of ABI breaking patches? >>>> >>> If you are talking ABI break if we load old DT which may lead to crash, we have .qos_requires_clocks flag which takes care of skipping QoS if required clocks are not enabled.we have addressed this issue through https://lore.kernel.org/all/20240704125515.22194-1-quic_okukatla@quicinc.com/ >> >> Format your emails correctly, it's difficult to read. >> >> Your binding did not require reg and clocks. Now it requires reg and >> clocks. This is called ABI break. >> >> Please follow Qualcomm extensive upstreaming guide, it explains this, >> doesn't it? Or follow writing bindings... >> > > Thanks for your review and guidance. > > I agree that adding reg and clocks properties to existing bindings is an > ABI break. The sa8775p is a relatively older platform, and when the > interconnect provider driver was initially upstreamed, QoS configuration > support was not available in the framework. As a result, QoS was not > enabled at that time. That's irrelevant reason. Writing bindings since long time ask pretty clearly to describe hardware completely, regardless whether Linux supports this or not. It does not matter if you enable QoS or not. > > The motivation for this change is that certain interconnect paths on > sa8775p require specific clocks to be enabled to access QoS registers. This does not look at all like existing device is completely broken. You just add new feature, so no ABI break. > 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? > concurrent workloads. Enabling QoS improves system responsiveness and > ensures more predictable behavior in high-throughput scenarios. Best regards, Krzysztof