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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-672c4d455ddsm7175365a12.18.2026.04.27.08.04.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Apr 2026 08:04:37 -0700 (PDT) Message-ID: Date: Mon, 27 Apr 2026 17:04:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@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: Val Packett , 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> <2f830f17-4bc5-4ebd-a66b-8068a14a871a@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-ORIG-GUID: JPyyxkdLfQwKiq7_PRapFEWrTBJjIV1t X-Authority-Analysis: v=2.4 cv=Xba5Co55 c=1 sm=1 tr=0 ts=69ef7b08 cx=c_pps a=nSjmGuzVYOmhOUYzIAhsAg==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=rs9IiGjxfO60RFTHbSYA:9 a=QEXdDO2ut3YA:10 a=1zu1i0D7hVQfj8NKfPKu:22 X-Proofpoint-GUID: JPyyxkdLfQwKiq7_PRapFEWrTBJjIV1t X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDI3MDE1OSBTYWx0ZWRfXyZ2AKhvje5z6 kS69jM0W13jhbxMXDk8kXCPKs3Id+seTN08kcL3mn5A3ny250/CGIz68QEefDvIGAJx+JUSVZg6 YXoLN33GVIsXToXQ7NfsH2+img+v939reVg2sMN02YFdVOwH3z0NTUVP61K1BkP2yO/EZJL8MHq Fwn4Kk2jPvwFp9Q7+1huijl2ry4G3mT0cJEXD29pvRAsnLFXSh51i0fGElre3uGx4GAUhLKBCRm b6dMfjHbaNpAu0HSC4N5DRFq1b1jJa0uSyAfeIFFtvp1CinD4tub+r2Wy5kreCBRGwYoyudNfTN wnoOtfH0hmW2q92A4z28wjQyLW+Q5fVFYIjfqxQmGTOzAkj/FjN8eMCRyOCmdW44T8bzav7Rl6p IBernpOa+ir4XD6jQAczW+MQy2XhEiDVripo16JJ6RAqLlZOFAtT3+BLpoNAJKVQYGgcbuV8bCs xIsvp5tBOgotaKA8+Vw== 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=2026-04-27_04,2026-04-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 bulkscore=0 suspectscore=0 phishscore=0 adultscore=0 impostorscore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2604270159 On 4/24/26 9:07 PM, Val Packett wrote: > > On 4/24/26 9:28 AM, Konrad Dybcio wrote: >> 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. > > lpass-cpu is also great from a "I don't want my pure libre operating system to touch dirty proprietary binary blobs" perspective, but you can definitely argue that that's not a genuine use case :) That's a genuine usecase, but probably not realistic (in the 'actually zero closed blobs' sense) today, if you want to have a featureful and stable system Konrad