Daniel Maslowski has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/33247
Change subject: Documentation: libgfxinit timing parameters ......................................................................
Documentation: libgfxinit timing parameters
Change-Id: I4b7743b0cc6c26e22dcd70f3dc3f466bc845b930 Signed-off-by: Daniel Maslowski daniel.maslowski@img.ly --- M Documentation/gfx/libgfxinit.md 1 file changed, 37 insertions(+), 0 deletions(-)
git pull ssh://review.coreboot.org:29418/coreboot refs/changes/47/33247/1
diff --git a/Documentation/gfx/libgfxinit.md b/Documentation/gfx/libgfxinit.md index c50761a..687323e 100644 --- a/Documentation/gfx/libgfxinit.md +++ b/Documentation/gfx/libgfxinit.md @@ -125,3 +125,40 @@ given order until all available pipes are taken. That's 1 pipe in VGA textmode, 2 pipes in high-resolution mode until Sandy Bridge, 3 pipes from Ivy Bridge on. + +GMA: Timing Parameters +---------------------- + +From the binary file `edid` in the sys filesystem on Linux, the panel can be +identified. The exact path may differ slightly. Here is an example: + +```sh +$ strings /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/edid +@0 5 +LG Display +LP140WF3-SPD1 +``` + +To figure out the timing parameters, refer to the [Intel Programmer's Reference +Manuals](https://01.org/linuxgraphics/documentation/hardware-specification-prms) +and try to find the datasheet of the panel using the information from `edid`. +In the example above, you would search for `LP140WF3-SPD1`. Find a table listing +the power sequence timing parameters, which are usually named T[N] and also +referenced in Intel's respective registers listing. You need the values for +`PP_ON_DELAYS`, `PP_OFF_DELAYS` and `PP_DIVISOR` for your `devicetree.cb`: + +```eval_rst ++----------------------------+---------------------------------------+--------+ +|Intel docs | devicetree.cb | Haswell| ++----------------------------+---------------------------------------+--------+ +|Power up delay | `gpu_panel_power_up_delay` | T3 | ++----------------------------+---------------------------------------+--------+ +|Power on to backlight on | `gpu_panel_power_backlight_on_delay` | T7 | ++----------------------------+---------------------------------------+--------+ +|Power Down delay | `gpu_panel_power_down_delay` | T10 | ++----------------------------+---------------------------------------+--------+ +|Backlight off to power down | `gpu_panel_power_backlight_off_delay` | T7 | ++----------------------------+---------------------------------------+--------+ +|Power Cycle Delay | `gpu_panel_power_cycle_delay` | T12 | ++----------------------------+---------------------------------------+--------+ +```