Daniel Maslowski has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/33246
Change subject: Documentation: libgfxinit timing parameters ......................................................................
Documentation: libgfxinit timing parameters
Change-Id: I94c2784ffcc12f54c285e1f90d73ff3905c4fae7 Signed-off-by: Daniel Maslowski daniel.maslowski@img.ly --- M Documentation/gfx/libgfxinit.md 1 file changed, 29 insertions(+), 0 deletions(-)
git pull ssh://review.coreboot.org:29418/coreboot refs/changes/46/33246/1
diff --git a/Documentation/gfx/libgfxinit.md b/Documentation/gfx/libgfxinit.md index c50761a..c19b10b 100644 --- a/Documentation/gfx/libgfxinit.md +++ b/Documentation/gfx/libgfxinit.md @@ -125,3 +125,32 @@ 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`: + +|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 |