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[84.253.213.87]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-59de491f9besm2544066e87.73.2026.01.26.02.49.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Jan 2026 02:49:08 -0800 (PST) Message-ID: Date: Mon, 26 Jan 2026 12:49:07 +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 v17 2/4] drm/msm/dpu: Defer SSPP allocation until CRTC check To: Jun Nie Cc: Abhinav Kumar , Dmitry Baryshkov , Sean Paul , Marijn Suijten , David Airlie , Simona Vetter , Rob Clark , Neil Armstrong , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20260121-msm-next-quad-pipe-split-v17-0-6eb6d8675ca2@linaro.org> <20260121-msm-next-quad-pipe-split-v17-2-6eb6d8675ca2@linaro.org> <6kzd2g4hgffqz5ipaqbourgiefuxxh3njj44n35blo37z6hhhj@us7lzlgmjuld> <91d590de-fa00-4df3-923f-b49ad00cd9da@oss.qualcomm.com> Content-Language: en-US From: Dmitry Baryshkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTI2MDA5MSBTYWx0ZWRfX8Y4TPzfU2iSh ACi7swT7jcUjsGKKLPJRBPKqu5VKQITAb8jVsNpTH5aYeGfpn4BPqAYoUxH1/0qSrjQzRZtemz8 8ZGoKpZLLBdoGDC0/sDyfHmRsCCaHlAEpxR1SkgOGM55bhhs/YE/2ySkkdSsPgY+pQgkbs+/2zg gsOl1+jIthTpLYDBLLJ8/g30qxCj9YntPDZyrxrOUuujRl2V0MeSGC2zdZl1CbaS3DqZ0m33ytB WI+jvbjtGrRA6ahbCJo47c9Xvmd3SReh/juLczt+76xK+0NZjrzZsYJggwQmc5+apPUg6cgaHIp FbqAgFY5DqbOFOHtglxcbkMdP8xwdWqhT3auemJP+3xw+kjHvnXZSts3BICknSNdyQP29QsAAfe Inhtr6qi90w07DLU6R4RuKMHW36BY8QJVdd+YFbvaPqYVcxfWi1xzfVJE0Ac9JUivtqmo7JjCiM oT3aENSACQj6COVmDGA== X-Proofpoint-ORIG-GUID: BYvg6wm6KWxdwW1EQcNrxYBM33z5KQZk X-Proofpoint-GUID: BYvg6wm6KWxdwW1EQcNrxYBM33z5KQZk X-Authority-Analysis: v=2.4 cv=c/imgB9l c=1 sm=1 tr=0 ts=697746a6 cx=c_pps a=5HAIKLe1ejAbszaTRHs9Ug==:117 a=oW9j1mrv7lfAxSiOe78TcA==:17 a=IkcTkHD0fZMA:10 a=vUbySO9Y5rIA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=EUspDBNiAAAA:8 a=_F_Q2RQ5sgb5A98PVdQA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=gYDTvv6II1OnSo0itH1n:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.20,FMLib:17.12.100.49 definitions=2026-01-26_02,2026-01-22_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 bulkscore=0 spamscore=0 malwarescore=0 lowpriorityscore=0 suspectscore=0 priorityscore=1501 clxscore=1015 phishscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2601260091 On 26/01/2026 12:29, Jun Nie wrote: > Dmitry Baryshkov 于2026年1月26日周一 18:13写道： >> >> On 26/01/2026 12:06, Jun Nie wrote: >>> Dmitry Baryshkov 于2026年1月22日周四 18:22写道： >>>> >>>> On Thu, Jan 22, 2026 at 02:03:25PM +0800, Jun Nie wrote: >>>>> Dmitry Baryshkov 于2026年1月21日周三 17:30写道： >>>>>> >>>>>> On Wed, Jan 21, 2026 at 04:01:51PM +0800, Jun Nie wrote: >>>>>>> Currently, plane splitting and SSPP allocation occur during the plane >>>>>>> check phase. Defer these operations until dpu_assign_plane_resources() >>>>>>> is called from the CRTC side to ensure the topology information from >>>>>>> the CRTC check is available. >>>>>> >>>>>> Why is it important? What is broken otherwise? >>>>> >>>>> I see. Thanks! Will add below lines in next version. >>>>> >>>>> By default, the plane check occurs before the CRTC check. >>>>> Without topology information from the CRTC, plane splitting >>>>> cannot be properly executed. Consequently, the SSPP >>>>> engine starts without a valid memory address, which triggers >>>>> an IOMMU warning. >>>> >>>> What is plane splitting? Write commit message for somebody who doesn't >>>> exactly know what is going on. >>> >>> Thanks for the suggestion! Any more revise is needed? >> >> Sadly enough the text below is not a significant improvement. >> >>> >>> Currently, splitting plane into SSPP rectangles the allocation occur >>> during the plane check phase, so that a plane can be supported by >>> multiple hardware pipe. >> >> What does this mean? Without virtual planes in place, there are no >> multiple hardware pipes. >> >>> While pipe topology is decided in CRTC check. >> >> ?? What does it mean here? >> >>> By default, the plane check occurs before the CRTC check in DRM >>> framework. Without topology information from the CRTC, plane splitting >>> cannot be properly executed. >> >> What does 'properly' mean here? How is it executed? What happens? >> >>> Consequently, the SSPP engine starts >>> without a valid memory address, which triggers IOMMU warning. >> >> IOMMU faults. There are no "warnings". >> >>> >>> Defer above plane operations until dpu_assign_plane_resources() >>> is called from the CRTC side to ensure the topology information from >>> the CRTC check is available. >> >> > Thanks for the patience! > > > Currently, splitting plane into SSPP rectangles and allocation occur > during the plane check phase. When virtual plane is enabled to support > quad-pipe topology later, 2 SSPPs with 4 rect will be needed, so that > a plane can be supported by 4 hardware pipes. And pipe number is number of pipes > decided in CRTC check per interface number, resolution and hardware > feature. Okay, but IOMMU errors were reported with virtual planes being disabled. So how is it relevant? > > By default, the plane check occurs before the CRTC check in DRM > framework. Without topology information from the CRTC, plane splitting WHat is plane splitting? > will be skipped for the first time as pipe number is 0. Consequently, > the SSPP engine starts without a valid memory address, which triggers > IOMMU fault. > > Defer above plane related operations until dpu_assign_plane_resources() > is called from the CRTC side to ensure the topology information from > the CRTC check is available. > > Regards, > Jun >> >> -- >> With best wishes >> Dmitry -- With best wishes Dmitry