1Display Panel Specifics 2======================= 3 4Timing Parameters 5----------------- 6 7From the binary file `edid` in the sys filesystem on Linux, the panel can be 8identified. The exact path may differ slightly. Here is an example: 9 10```sh 11$ strings /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/edid 12@0 5 13LG Display 14LP140WF3-SPD1 15``` 16 17To figure out the timing parameters, refer to the [Intel Programmer's Reference 18Manuals](https://01.org/linuxgraphics/documentation/hardware-specification-prms) 19and try to find the datasheet of the panel using the information from `edid`. 20In the example above, you would search for `LP140WF3-SPD1`. Find a table listing 21the power sequence timing parameters, which are usually named T[N] and also 22referenced in Intel's respective registers listing. You need the values for 23`PP_ON_DELAYS`, `PP_OFF_DELAYS` and `PP_DIVISOR` for your `devicetree.cb`: 24 25```{eval-rst} 26+-----------------------------+---------------------------------------+-----+ 27| Intel docs | devicetree.cb | eDP | 28+-----------------------------+---------------------------------------+-----+ 29| Power up delay | `gpu_panel_power_up_delay` | T3 | 30+-----------------------------+---------------------------------------+-----+ 31| Power on to backlight on | `gpu_panel_power_backlight_on_delay` | T7 | 32+-----------------------------+---------------------------------------+-----+ 33| Power Down delay | `gpu_panel_power_down_delay` | T10 | 34+-----------------------------+---------------------------------------+-----+ 35| Backlight off to power down | `gpu_panel_power_backlight_off_delay` | T9 | 36+-----------------------------+---------------------------------------+-----+ 37| Power Cycle Delay | `gpu_panel_power_cycle_delay` | T12 | 38+-----------------------------+---------------------------------------+-----+ 39``` 40 41Intel GPU Tools and VBT 42----------------------- 43 44The Intel GPU tools are in a package called either `intel-gpu-tools` or 45`igt-gpu-tools` in most distributions of Linux-based operating systems. 46In the coreboot `util/` directory, you can find `intelvbttool`. 47 48From a running system, you can dump the register values directly: 49```sh 50$ intel_reg dump --all | grep PCH_PP 51 PCH_PP_STATUS (0x000c7200): 0x80000008 52 PCH_PP_CONTROL (0x000c7204): 0x00000007 53 PCH_PP_ON_DELAYS (0x000c7208): 0x07d00001 54 PCH_PP_OFF_DELAYS (0x000c720c): 0x01f40001 55 PCH_PP_DIVISOR (0x000c7210): 0x0004af06 56``` 57 58You can obtain the timing values from a VBT (Video BIOS Table), which you can 59dump from a vendor UEFI image: 60```sh 61$ intel_vbt_decode data.vbt | grep T3 62 Power Sequence: T3 2000 T7 10 T9 2000 T10 500 T12 5000 63 T3 optimization: no 64``` 65