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Mon, 09 Nov 2026 20:14:50 -0800 (PST) Received: from [10.64.69.173] ([114.94.8.21]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2edb6d4d838sm4208715ad.12.2026.11.09.20.14.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Nov 2026 20:14:49 -0800 (PST) Message-ID: Date: Tue, 10 Nov 2026 12:14:45 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 00/35] drm/msm/dp: Add MST support for MSM chipsets To: Robert Meijers Cc: abhinav.kumar@linux.dev, airlied@gmail.com, dmitry.baryshkov@oss.qualcomm.com, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, jesszhan0024@gmail.com, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, lumag@kernel.org, marijn.suijten@somainline.org, quic_abhinavk@quicinc.com, robin.clark@oss.qualcomm.com, sean@poorly.run, simona@ffwll.ch, stable@vger.kernel.org References: <20260929-msm-dp-mst-v7-0-4b81473185e7@oss.qualcomm.com> Content-Language: en-US From: Yongxing Mou In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: BiObxGJ3fzVxVBzZHzc3glb-G5SXKSK_ X-Proofpoint-Spam-Info: AW1haW4tMjYxMTEwMDAxNiBTYWx0ZWRfX4nu00nETu2gO PyY17h7ElJGjh0VY2V665kf6Dw5y1aZoUzj+fiPQcL5Jl3zlxy2QoXYzE1KTRDucBRztvgTD+QG QBO3rognONqzoiuC/IzoJgeQiRjLzZ8= X-Authority-Analysis: v=2.4 cv=TOrQ2Fla c=1 sm=1 tr=0 ts=6af29a3b cx=c_pps a=JL+w9abYAAE89/QcEU+0QA==:117 a=Uz3yg00KUFJ2y2WijEJ4bw==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yx91gb_oNiZeI1HMLzn7:22 a=dRm9NI7_ec0In7u_rNMA:9 a=QEXdDO2ut3YA:10 a=324X-CrmTo6CU4MGRt3R:22 X-Proofpoint-ORIG-GUID: BiObxGJ3fzVxVBzZHzc3glb-G5SXKSK_ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTEwMDAxNiBTYWx0ZWRfX6n1tkyTtDt5n v6wwRfbhXqZQUlUTySr5aVPOK3gsOrMnz6EAxTnEMOaWhV1jdC5exfZt0uDCRPlTzSZY6wQNYyv aE7NT10glNPTOjsxQ5jrHwhNkekldniT7F6A0Pa+n9G9UKpwnlZvqMsSiQCv8egeM/HFnHLHR6S cl1b75SIL0mp4BP+f31eivIGXdLDH+iuw55gUDfX5bgBzteRHoeWycJgkPVTIgXsYgvTKIFVkkm DwiEVuLBLuWcLILJNoXmbg7RuXMNTO6BnjiGlUC4ZAH0soRZq4a5kv0Ff0XLsj+kS+P17s748jG KvQw1I47N4KlV2PG642bO4/H+/QLbGZ0LQ3xyjqLuFVY6x0t2YHNwEG1CbumYfPhINK8gK1PQCx zIuZFVpU9CTtoO2NSBq4l2WdFGmTwq8mK8pjNijEqzWQsM/drdfKvRHi6Wr3F1V2xPcVpfGFHdh 2lG/DOOYDeq+Axpm7vA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-10_02,2026-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 bulkscore=0 priorityscore=1501 impostorscore=0 phishscore=0 clxscore=1015 spamscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611100016 On 10/28/2026 5:04 AM, Robert Meijers wrote: > Hi, > > ((Sorry, re-sending because the first was rejected for not being plain > text)) > (First up this is the first time I'm participating on a mailing list, > so sorry in advance if I'm doing something wrong). > >> Add support for Multi-stream transport for MSM chipsets that allow > a >> single instance of DP controller to send multiple streams. > > > This series has been validated on sa8775p ride platform using multiple > > MST dongles and also daisy chain method on both DP0 and DP1 upto 1080P. > > > With 4x4K monitors, due to lack of layer mixers that combination > will > not > work but this can be supported as well after some rework on > the DPU > side. > > In addition, SST was re-validated with all these > changes to ensure > there > were no regressions. > I have applied this patch series onto a near mainline 7.3 tree for the > Xiaomi Pad 6s Pro ("Sheng"), with SM8550. But with these patches > applied I don't have working audio, over USB-C to my (DisplayPort) > monitor, anymore. If I disable MST support on the monitor audio works > again. Debugging (using AI) reveals that the DP0 Jack is not reported as > connected anymore when connected to the monitor, with these patches > applied and MST enabled on the monitor. As shown, for example, by > amixer: > > $ amixer -c 0 contents | grep -i -A8 -B3 -E 'hdmi|displayport|jack' > numid=208,iface=CARD,name='DP0 Jack' > ; type=BOOLEAN,access=r-------,values=1 > : values=off > > With MST on the monitor disabled this outputs "values=on". The same is > also reflected by "pactl list cards" and "pactl list sinks" where > HDMI/DisplayPort is reported as "not available" with MST enabled (and > "available" when disabling MST). > > (Again, suggested by AI) I also checked the ELD, which in both > cases (MST on and off on the monitor) is identical, including audio > information (like "speakers [0x1] FL/FR"). (Also, audio works both using > an AMD and an Intel based laptop, in which case I can also choose > whether to use "HDMI" or "HDMI 2" to switch audio output between two > monitors, in daisy chain). > > So my foremost question is: should audio be supported in case of MST, > after applying these patches? Or is this possibly out of scope? > Not supported yet. Audio is only wired up on the SST bridge, and the MST connectors don't register an audio device at all. Once MST is active the SST bridge reports disconnected on purpose, so the jack never comes up. Nothing wrong with your tree. > For clarity I would also like to note that without these patches > applied audio over DP does work as well, irrespective of MST being > on or off on the monitor (obviously always running as SST because of > missing kernel support). Which would make me believe that no audio > support in the same setup might be considered a regression? > > Note that I do understand that me running a forked kernel on a > (by upstream) unsupported device might also lead to issues or require > changes for the fork. And that if audio does work with MST then this is > something the maintainers of the fork should, most likely, fix. But > from the cover letter and commit messages it is unclear to me whether > audio support should work and/or has been tested when MST is in use. > > Kind regards, > Robert >