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[84.253.213.87]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-59de48e5d0asm2542556e87.22.2026.01.26.02.13.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Jan 2026 02:13:28 -0800 (PST) Message-ID: <91d590de-fa00-4df3-923f-b49ad00cd9da@oss.qualcomm.com> Date: Mon, 26 Jan 2026 12:13:27 +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> 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: AW1haW4tMjYwMTI2MDA4NyBTYWx0ZWRfX4Quk5pfxCADb tINj9X8rSw21y4G15C/hBKHIDpFOsR3Rv5gd8WJFSVPGZvaSa9ep8O6J3URIzGfvHnIm3INeAmL NYLE4KVTehdACx4+/BOY/N5FzkC2g/EGSYgm2SS6+BnZUR9o85PFULDV+WZJ+gBAd4799ZVLZ6O JUMCG1QLefPUEvax5D938ilRnB2oZIal3Zyg5MxtNPL+OE6Rb+GD5urF/dsdR97ZAvZ+hjP+q2Z nCNESiWBg5QvW+9TJbkD7l3KGTvTHct78tVqrdwS5ZA2PnI00uhwWdbyMpixJPv7RcGmcXDCb9x P9pWsQJQMcswV64N1lqBVg6WchUL5P2znbwxanFibrfNUUl0ek7DNPKotlwYSX4E+vcSLfWJWOX KtmvXOIk5MBBQB2CucM46VIwckBuV/6wugEGL+NY3f1z8BUamVnq+xh6W9jDvF+OkM1tn15gUyd GLGgzQYTND2THieByYQ== X-Authority-Analysis: v=2.4 cv=QN5lhwLL c=1 sm=1 tr=0 ts=69773e4a cx=c_pps a=DUEm7b3gzWu7BqY5nP7+9g==:117 a=oW9j1mrv7lfAxSiOe78TcA==:17 a=IkcTkHD0fZMA:10 a=vUbySO9Y5rIA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=EUspDBNiAAAA:8 a=JU2WE-GTjbXmrkkuVJ4A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=-aSRE8QhW-JAV6biHavz:22 X-Proofpoint-GUID: V83lSjYvgjijkP2cOuI6wid6ouFgWeXL X-Proofpoint-ORIG-GUID: V83lSjYvgjijkP2cOuI6wid6ouFgWeXL 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 phishscore=0 clxscore=1015 adultscore=0 malwarescore=0 suspectscore=0 impostorscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2601260087 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. -- With best wishes Dmitry