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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8ebb33fcsm22424008b3a.33.2026.04.24.05.28.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Apr 2026 05:28:57 -0700 (PDT) Message-ID: <2f830f17-4bc5-4ebd-a66b-8068a14a871a@oss.qualcomm.com> Date: Fri, 24 Apr 2026 14:28:42 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 12/12] arm64: dts: qcom: qcs6490-radxa-dragon-q6a: add LPASS CPU audio variant To: Xilin Wu , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Dmitry Baryshkov , Liam Girdwood , Mark Brown , Judy Hsiao , Srinivas Kandagatla Cc: linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-sound@vger.kernel.org References: <20260407-dragon-q6a-feat-fixes-v1-0-14aca49dde3d@radxa.com> <20260407-dragon-q6a-feat-fixes-v1-12-14aca49dde3d@radxa.com> <29a7dd01-7513-4fe5-8546-d57757b3b2d0@oss.qualcomm.com> <88B7BBB9133FBAD1+ccb025ea-4999-4701-bb18-c57a42cabe2f@radxa.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <88B7BBB9133FBAD1+ccb025ea-4999-4701-bb18-c57a42cabe2f@radxa.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDI0MDExNyBTYWx0ZWRfX4pHm/Q+v9hVw nyi2VDPFjzC2aakR8SbJObLwabjOa1AID33nXLnw74BRDQk2g1Uh0YJZvp3r/hxxhGozMN+KQBf 5Zz4nT0bSqrs1aXZ1o/97EUuWu7YzUuAw9VTIHoNBmCVC8S+yGOdJTIM2zLQYtdedh6dTmSVYpI FyCZgGVSYVX4h5vUDIEMsActBCqO6FyPnexScah/SK55bM8rkB5SL6XEMr5Z6eCvnA3uFDS6vJl hiG1OSEihRpP5UGpEaNwZIVm8pHz7wKaEEnuNEZE3Mau1NtwaJUjRBTqUity5/Jrxsu9Qk7556Z MNb/qNiZ5S8yV4CQek5E2Su1BzhjaeHaxHq4cCjaZfP8eKVyUd2WgceplOdiZA58HPZnOs9fLKe +0/Gj2eGCHsRjzUANFgQgSkyVjrEIiooO5MadKTxx+B1THvAq/moTwYGVeu/bZeym/cHW6YbTa+ LL+A4O2/1xQvbJvfGRA== X-Authority-Analysis: v=2.4 cv=UqpT8ewB c=1 sm=1 tr=0 ts=69eb620a cx=c_pps a=Qgeoaf8Lrialg5Z894R3/Q==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=KYwSRLHedoOKSWcoqLUA:9 a=QEXdDO2ut3YA:10 a=x9snwWr2DeNwDh03kgHS:22 X-Proofpoint-ORIG-GUID: RuF1zd479ujkcWy4oDnmV1O7Az8-bYKt X-Proofpoint-GUID: RuF1zd479ujkcWy4oDnmV1O7Az8-bYKt X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-23_03,2026-04-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 lowpriorityscore=0 impostorscore=0 phishscore=0 adultscore=0 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2604240117 On 4/8/26 11:47 AM, Xilin Wu wrote: > On 4/8/2026 5:06 PM, Konrad Dybcio wrote: >> On 4/7/26 5:20 PM, Xilin Wu wrote: >>> Add a qcs6490-radxa-dragon-q6a-lpass-cpu.dts variant for debugging and >>> bring-up of the host-controlled LPASS audio path on the Radxa Dragon >>> Q6A. >>> >>> This variant enables the LPASS blocks and codec macros needed by the >>> lpass-cpu driver, wires WCD9380 playback/capture and DisplayPort audio >>> to the LPASS CDC DMA and DP interfaces, and disables remoteproc_adsp so >>> that the audio hardware is owned directly by Linux. >>> >>> This DTB is an optional configuration for systems booted with the kernel >>> running at EL2, where direct CPU access to the LPASS hardware is >>> available. It is useful for users who need low-latency and fully >>> controllable audio. >> >> I believe on Chrome platforms it was done this way because at some point >> it was determined that they would specifically like not to use the DSP. >> >> I think this is more of a hack than anything else.. but at the end of the >> commit message you mention low latency - is the impact actually measurable? >> > > Some of our users also specifically prefer not to use the DSP [1] :) > > Based on their testing, the AudioReach/ADSP path imposes a minimum scheduling interval of 10 ms, which is much higher than the 0.67 ms they can get on a Raspberry Pi 5 with direct I2S/DMA. We passed on this feedback. > Since the lpass-cpu setup works properly, I would not consider this a hack. Well yeah it works, but I was really hoping it would be made unnecessary and available for removal sooner or later.. But since there's a genuine usecase, perhaps not. Konrad