Daniel Maslowski has uploaded this change for review.

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Documentation: libgfxinit timing parameters

Change-Id: I8bc86c480a4f7d2e7f3044ca245c8722c09e7590
Signed-off-by: Daniel Maslowski <daniel.maslowski@img.ly>
---
A Documentation/gfx/intel-gma.md
M Documentation/gfx/libgfxinit.md
M Documentation/index.md
3 files changed, 43 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/66/33266/1

diff --git a/Documentation/gfx/intel-gma.md b/Documentation/gfx/intel-gma.md
new file mode 100644
index 0000000..d6a3992
--- /dev/null
+++ b/Documentation/gfx/intel-gma.md
@@ -0,0 +1,39 @@
+Intel GMA (Graphics Media Accelerator) Specifics
+================================================
+
+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    |
++----------------------------+---------------------------------------+--------+
+```
diff --git a/Documentation/gfx/libgfxinit.md b/Documentation/gfx/libgfxinit.md
index c50761a..4c6b6f0 100644
--- a/Documentation/gfx/libgfxinit.md
+++ b/Documentation/gfx/libgfxinit.md
@@ -55,6 +55,9 @@
 GMA: Per Board Configuration
 ----------------------------
 
+In order to set up the display panel, see the
+[specifics for Intel GMA](/gfx/intel-gma.md).
+
 There are a few Kconfig symbols to consider. To indicate that a
 board can initialize graphics through *libgfxinit*:
 
diff --git a/Documentation/index.md b/Documentation/index.md
index 6dbbf4d..8e18f4a 100644
--- a/Documentation/index.md
+++ b/Documentation/index.md
@@ -173,6 +173,7 @@
 * [Dealing with Untrusted Input in SMM](technotes/2017-02-dealing-with-untrusted-input-in-smm.md)
 * [GPIO toggling in ACPI AML](acpi/gpio.md)
 * [Native Graphics Initialization with libgfxinit](gfx/libgfxinit.md)
+* [Intel GMA specifics](gfx/intel-gma.md)
 * [Architecture-specific documentation](arch/index.md)
 * [Northbridge-specific documentation](northbridge/index.md)
 * [System on Chip-specific documentation](soc/index.md)

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