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Thu, 17 Oct 2024 19:00:18 +0000 Message-ID: <871b2ee7-4221-4223-b2ea-243f7cedcca6@amd.com> Date: Thu, 17 Oct 2024 14:00:16 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] Documentation/gpu: Document how to narrow down display issues To: Rodrigo Siqueira , amd-gfx@lists.freedesktop.org Cc: Leo Li , Aurabindo Pillai , Hamza Mahfooz , Harry Wentland , Christian Konig , Alex Deucher References: <20241017034244.223993-1-Rodrigo.Siqueira@amd.com> <20241017034244.223993-2-Rodrigo.Siqueira@amd.com> Content-Language: en-US From: Mario Limonciello In-Reply-To: <20241017034244.223993-2-Rodrigo.Siqueira@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SN6PR2101CA0024.namprd21.prod.outlook.com (2603:10b6:805:106::34) To MN0PR12MB6101.namprd12.prod.outlook.com (2603:10b6:208:3cb::10) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN0PR12MB6101:EE_|IA0PR12MB7749:EE_ X-MS-Office365-Filtering-Correlation-Id: 307d1c02-9727-4f53-a2e1-08dceeddf12d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014; 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This page introduces debug mechanisms and > +procedures to help you identify if some issues are related to display code. > + > +Narrow down display issues > +========================== > + > +Since the display is the driver's visual component, it is common to see users > +reporting issues as a display when another component causes the problem. This > +section equips users to determine if a specific issue was caused by the display > +component or another part of the driver. > + > +DC dmesg important messages > +--------------------------- > + > +The dmesg log is the first source of information to be checked, and amdgpu > +takes advantage of this feature by logging some valuable information. When > +looking for the issues associated with amdgpu, remember that each component of > +the driver (e.g., smu, PSP, dm, etc.) is loaded one by one, and this > +information can be found in the dmesg log. In this sense, look for the part of > +the log that looks like the below log snippet:: > + > + [ 4.254295] [drm] initializing kernel modesetting (IP DISCOVERY 0x1002:0x744C 0x1002:0x0E3B 0xC8). > + [ 4.254718] [drm] register mmio base: 0xFCB00000 > + [ 4.254918] [drm] register mmio size: 1048576 > + [ 4.260095] [drm] add ip block number 0 > + [ 4.260318] [drm] add ip block number 1 > + [ 4.260510] [drm] add ip block number 2 > + [ 4.260696] [drm] add ip block number 3 > + [ 4.260878] [drm] add ip block number 4 > + [ 4.261057] [drm] add ip block number 5 > + [ 4.261231] [drm] add ip block number 6 > + [ 4.261402] [drm] add ip block number 7 > + [ 4.261568] [drm] add ip block number 8 > + [ 4.261729] [drm] add ip block number 9 > + [ 4.261887] [drm] add ip block number 10 > + > +From the above example, you can see the line that reports that ``, > +(**Display Manager**), was loaded, which means that display can be part of the > +issue. If you do not see that line, something else might have failed before > +amdgpu loads the display component, indicating that we don't have a > +display issue. > + > +After you identified that the DM was loaded correctly, you can check for the > +display version of the hardware in use, which can be retrieved from the dmesg > +log with the command:: > + > + dmesg | grep -i 'display core' > + > +This command shows a message that looks like this:: > + > + [ 4.655828] [drm] Display Core v3.2.285 initialized on DCN 3.2 > + > +This message has two key pieces of information: > + > +* **The DC version (e.g., v3.2.285)**: Display developers release a new DC version > + every week, and this information can be advantageous in a situation where a > + user/developer must find a good point versus a bad point based on a tested > + version of the display code. Remember from page :ref:`Display Core `, > + that every week the new patches for display are heavily tested with IGT and > + manual tests. > +* **The DCN version (e.g., DCN 3.2)**: The DCN block is associated with the > + hardware generation, and the DCN version conveys the hardware generation that > + the driver is currently running. This information helps to narrow down the > + code debug area since each DCN version has its files in the DC folder per DCN > + component (from the example, the developer might want to focus on > + files/folders/functions/structs with the dcn32 label might be executed). > + However, keep in mind that DC reuses code across different DCN versions; for > + example, it is expected to have some callbacks set in one DCN that are the same > + as those from another DCN. In summary, use the DCN version just as a guide. > + > +From the dmesg file, it is also possible to get the ATOM bios code by using:: > + > + dmesg | grep -i 'ATOM BIOS' > + > +Which generates an output that looks like this:: > + > + [ 4.274534] amdgpu: ATOM BIOS: 113-D7020100-102 > + > +This type of information is useful to be reported. > + > +Avoid loading display core > +-------------------------- > + > +Sometimes, it might be hard to figure out which part of the driver is causing > +the issue; if you suspect that the display is not part of the problem and your > +bug scenario is simple (e.g., some desktop configuration) you can try to remove > +the display component from the equation. First, you need to identify `dm` ID > +from the dmesg log; for example, search for the following log:: > + > + [ 4.254295] [drm] initializing kernel modesetting (IP DISCOVERY 0x1002:0x744C 0x1002:0x0E3B 0xC8). > + [..] > + [ 4.260095] [drm] add ip block number 0 > + [ 4.260318] [drm] add ip block number 1 > + [..] > + [ 4.261057] [drm] add ip block number 5 > + > +Notice from the above example that the `dm` id is 5 for this specific hardware. > +Next, you need to run the following binary operation to identify the IP block > +mask:: > + > + 0xffffffff & ~(1 << [DM ID]) > + > +From our example the IP mask is:: > + > + 0xffffffff & ~(1 << 5) = 0xffffffdf > + > +Finally, to disable DC, you just need to set the below parameter in your > +bootloader:: > + > + amdgpu.ip_block_mask = 0xffffffdf > + > +If you can boot your system with the DC disabled and still see the issue, it > +means you can rule DC out of the equation. However, if the bug disappears, you > +still need to consider the DC part of the problem and keep narrowing down the > +issue. In some scenarios, disabling DC is impossible since it might be > +necessary to use the display component to reproduce the issue (e.g., play a > +game). > + > +**Note: This will probably lead to the absence of a display output.** > + > +Display flickering > +------------------ > + > +Display flickering might have multiple causes; one is the lack of proper power > +to the GPU or problems in the DPM switches. A good first generic verification > +is to set the GPU to use high voltage:: > + > + bash -c "echo high > /sys/class/drm/card0/device/power_dpm_force_performance_level" > + > +The above command sets the GPU/APU to use the maximum power allowed which > +disables DPM switches. If forcing DPM levels high does not fix the issue, it > +is less likely that the issue is related to power management. If the issue > +disappears, there is a good chance that other components might be involved, and > +the display should not be ignored since this could be a DPM issues. From the > +display side, if the power increase fixes the issue, it is worth debugging the > +clock configuration and the pipe split police used in the specific > +configuration. > + > +Display artifacts > +----------------- > + > +Users may see some screen artifacts that can be categorized into two different > +types: localized artifacts and general artifacts. The localized artifacts > +happen in some specific areas, such as around the UI window corners; if you see > +this type of issue, there is a considerable chance that you have a userspace > +problem, likely Mesa or similar. The general artifacts usually happen on the > +entire screen. They might be caused by a misconfiguration at the driver level > +of the display parameters, but the userspace might also cause this issue. One > +way to identify the source of the problem is to take a screenshot or make a > +desktop video capture when the problem happens; after checking the > +screenshot/video recording, if you don't see any of the artifacts, it means > +that the issue is likely on the the driver side. If you can still see the > +problem in the data collected, it is an issue that probably happened during > +rendering, and the display code just got the framebuffer already corrupted. > + > +Disabling/Enabling specific features > +==================================== > + > +DC has a struct named `dc_debug_options`, which is statically initialized by > +all DCE/DCN components based on the specific hardware characteristic. This > +structure usually facilitates the bring-up phase since developers can start > +with many disabled features and enable them individually. This is also an > +important debug feature since users can change it when debugging specific > +issues. > + > +For example, dGPU users sometimes see a problem where a horizontal fillet of > +flickering happens in some specific part of the screen. This could be an > +indication of Sub-Viewport issues; after the users identified the target DCN, > +they can set the `force_disable_subvp` field to true in the statically > +initialized version of `dc_debug_options` to see if the issue gets fixed. Along > +the same lines, users/developers can also try to turn off `fams2_config` and > +`enable_single_display_2to1_odm_policy`. In summary, the `dc_debug_options` is > +an interesting form for identifying the problem. > + > DC Visual Confirmation > ====================== > > @@ -76,6 +251,18 @@ change in real-time by using something like:: > When reporting a bug related to DC, consider attaching this log before and > after you reproduce the bug. > > +Collect Firmware information > +============================ > + > +When reporting issues, it is important to have the firmware information since > +it can be helpful for debugging purposes. To get all the firmware information, > +use the command:: > + > + cat /sys/kernel/debug/dri/0/amdgpu_firmware_info > + > +From the display perspective, pay attention to the firmware of the DMCU and > +DMCUB. > + > DMUB Firmware Debug > =================== >