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[2001:14bb:a6:738a:e519:cad2:e720:53eb]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54fc645cee9sm305198e87.75.2025.05.09.08.18.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 May 2025 08:18:41 -0700 (PDT) Message-ID: <6cfc706f-4909-4121-9849-a37e4769ab2f@oss.qualcomm.com> Date: Fri, 9 May 2025 18:18:40 +0300 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 v9 01/14] drm/atomic-helper: Add crtc check before checking plane To: Jun Nie Cc: Rob Clark , Abhinav Kumar , Sean Paul , Marijn Suijten , David Airlie , Simona Vetter , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20250506-quad-pipe-upstream-v9-0-f7b273a8cc80@linaro.org> <20250506-quad-pipe-upstream-v9-1-f7b273a8cc80@linaro.org> Content-Language: en-US From: Dmitry Baryshkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=M7xNKzws c=1 sm=1 tr=0 ts=681e1cd4 cx=c_pps a=50t2pK5VMbmlHzFWWp8p/g==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=EUspDBNiAAAA:8 a=KKAkSRfTAAAA:8 a=sWdYkf8P3oHYA_MdvdkA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=IoWCM6iH3mJn3m4BftBB:22 a=cvBusfyB2V15izCimMoJ:22 X-Proofpoint-ORIG-GUID: 0TXHz23R4sLsjsTI1h8rfoZVZuzFXjjS X-Proofpoint-GUID: 0TXHz23R4sLsjsTI1h8rfoZVZuzFXjjS X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTA5MDE1MSBTYWx0ZWRfXwJ9SkJDgVqbd BWdt8v1+vbgJH3EZCXXekQt7fCL+1uc6E4LhDV41lYVA0qaw1Ez2oIac0UwopqByUmt22GRqZDk hgmPuaWTCpSb4Jt/5USIRP1ovLQn0dXrUp3ixiYlPVdF7pIq3Ff35fGQaesSuoUtI+YRVV1Qaqp 5nn8OAXZKcwrjxRQ5mCIOqaZTeU86EBkqXtyEFsd881qTQOmzq3qOTjcMLTuHS4eZmznLTSCgYe QcDntno6O6hrcL5rtyzDKxIe6pnIE0NR875tPCcGlWs9n4ux1Fu3/W/reFpvL6HrwN4Gv0Se5uj Fw8++UKpp7ZR669uGaf7z3xQyMdDHb8ewtbHXNPIw7ivwxAdLQb0iwSbVWK78rV+B9nXd/su5K6 wU/UcdiKMKWpSjwnczDPJ4noPAJ9Wl+K4JtPr682D9OCHkNVrUnawKFU2OtftXMmvb3PkWEv X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-09_06,2025-05-09_01,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 priorityscore=1501 spamscore=0 mlxlogscore=999 bulkscore=0 impostorscore=0 clxscore=1015 suspectscore=0 adultscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505090151 On 09/05/2025 06:08, Jun Nie wrote: > Dmitry Baryshkov 于2025年5月8日周四 18:47写道： >> >> On Tue, May 06, 2025 at 11:47:31PM +0800, Jun Nie wrote: >>> Some display controller support flexible CRTC and DMA, such as the display >>> controllers in snapdragon SoCs. CRTC can be implemented with several mixers >>> in parallel, and plane fetching can be implemented with several DMA under >>> umberala of a virtual drm plane. >>> >>> The mixer number is decided per panel resolution and clock rate constrain >>> first, which happens in CRTC side. Then plane is split per mixer number >>> and configure DMA accordingly. >> >> Here you are describing a behaviour of one particular driver as a reason >> to change the framework. > > Yeah, the specific driver requires a change in framework. Maybe the > comment is not > proper? Yes. Explain how does that benefit the framework / other drivers. Otherwise the answer would be as simple as 'replace drm_atomic_helper_check_planes() in your driver'. >> >>> >>> To support such forthcoming usage case, CRTC checking shall happen before >>> checking plane. Add the checking in the drm_atomic_helper_check_modeset(). >> >> So, now drivers will get two calls to atomic_check(), one coming in >> circumstances which were not expected by the drivers before. Are you >> sure that this won't break anything? > > Yes, it is a concern. Is there any way to limit the change in > framework to specific > driver with a flag, such as DRM_FLAG_CHECK_CRTC_BEFORE_PLANE? Definitely not with a flag. You can try adding a new helper callback, but I don't know how DRM core maintainers would react to it. >> >>> >>> Signed-off-by: Jun Nie >>> --- >>> drivers/gpu/drm/drm_atomic_helper.c | 19 +++++++++++++++++++ >>> 1 file changed, 19 insertions(+) >>> >>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c >>> index 5302ab3248985d3e0a47e40fd3deb7ad0d9f775b..5bca4c9683838c38574c8cb7c0bc9d57960314fe 100644 >>> --- a/drivers/gpu/drm/drm_atomic_helper.c >>> +++ b/drivers/gpu/drm/drm_atomic_helper.c >>> @@ -816,6 +816,25 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, >>> return ret; >>> } >>> >>> + for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) { >>> + const struct drm_crtc_helper_funcs *funcs; >>> + >>> + funcs = crtc->helper_private; >>> + >>> + if (!funcs || !funcs->atomic_check) >>> + continue; >>> + >>> + ret = funcs->atomic_check(crtc, state); >>> + if (ret) { >>> + drm_dbg_atomic(crtc->dev, >>> + "[CRTC:%d:%s] atomic driver check failed\n", >>> + crtc->base.id, crtc->name); >>> + return ret; >>> + } >>> + } >>> + >>> + >>> + >> >> Too many empty lines. But the main quesiton is: why are you calling it >> before mode_valid()? According to your description a better place would >> be in drm_atomic_helper_check_planes(). >> > Agree, that's the proper function. Will remove the empty line in next version. > >>> ret = mode_valid(state); >>> if (ret) >>> return ret; >>> >>> -- >>> 2.34.1 >>> >> >> -- >> With best wishes >> Dmitry >> -- With best wishes Dmitry