Daniel Maslowski has uploaded this change for review.
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 |
++----------------------------+---------------------------------------+--------+
+```
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