| commit | 94fb916ea6ab1e6ae901e5ab264d4e1e8e8b5f2b | [log] [tgz] |
|---|---|---|
| author | Nico Huber <nico.huber@secunet.com> | Fri May 10 13:44:11 2019 +0200 |
| committer | Nico Huber <nico.h@gmx.de> | Sat Jul 20 16:34:01 2019 +0000 |
| tree | e0d6052ceefda16e21c60af73c707fbcb41e4b1e | |
| parent | f80c3e4e103dcd717825158d274ffcbae648ff0b [diff] |
dp training: Write correct training data when switching patterns
Apparently this was wrong all the time. When switching the training
pattern, i.e. writes to DPCD+0x102, we also have to write the current
signal levels to subsequent offsets. We always wrote 0s in this case,
even if we already negotiated higher values during the clock-recovery
phase. Obviously, this results in havoc if the sink takes the 0s
serious.
TEST=Run a few hundred training rounds with a Terra 2462W display.
This display almost always requested an increase of the voltage
swing to level 1. Trainings where it recovered the clock with
level 0 always succeeded, while trainings with level 1 almost
always lost synchronization at the start of channel equalization.
With the patch applied, all trainings succeeded.
Change-Id: I6ae2f9aaec0b042e8dee6e8b0099ea62c82f611b
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/32732
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
libgfxinit is a graphics initialization (aka modesetting) library for embedded environments. It currently supports only Intel hardware, more specifically the Intel Core processor line.
It can query and set up most kinds of displays based on their EDID information. You can, however, also specify particular mode lines.
libgfxinit is written in SPARK, an Ada subset with formal verifica- tion aspects. Absence of runtime errors can be proved automatically with SPARK GPL 2016.
For compilation, the GNAT Ada compiler is required. Usual package names in Linux distributions are gcc-ada and gnat.
You'll need libhwbase and libgfxinit. Best is to clone the reposi- tories into a common parent directory (this way libgfxinit will know where to find libhwbase).
$ mkdir gfxfun && cd gfxfun $ git clone https://review.coreboot.org/p/libhwbase.git $ git clone https://review.coreboot.org/p/libgfxinit.git
Both libraries are currently configured by hand-written config files. You can either write your own .config, link one of the shipped files in configs/, e.g.:
$ ln -s configs/linux libhwbase/.config
or overwrite the config filename by specifying cnf=<configfile> on the make command line.
By default most debug messages won't be compiled into the binary. To include them into the build, set DEBUG=1 on the command line or in your .config.
Let's install libhwbase. We'll need configs/linux to build regular Linux executables:
$ cd libhwbase $ make DEBUG=1 cnf=configs/linux install
By default this installs into a new subdirectory dest. You can however overwrite this decision by specifying DESTDIR=.
gfx_testlibgfxinit is configured and installed in the same manner as de- scribed above. You will have to select a configuration matching your hardware.
The makefile knows an additional target gfx_test to build a small Linux test application:
$ cd ../libgfxinit $ make DEBUG=1 cnf=configs/sandybridge gfx_test
The resulting binary is build/gfx_test.
gfx_test sets up its own framebuffer in the stolen memory. It backs any current framebuffer mapping and contents up first and re- stores it before exiting. This works somehow even while the i915 driver is running. A wrapper script gfxtest/gfx_test.sh is pro- vided to help with the setup. It switches to a text console first and tries to unload the i915 driver. But ignores failures to do so (it won't work if you still have any application running that uses the gfx driver, e.g. an X server).
# gfxtest/gfx_test.sh
If you chose the right config above, you should be presented with a nice test image. But please be prepared that your console might be stuck in that state afterwards. You can try to run it with i915 deactivated then (e.g. when booting with nomodeset in the kernel command line or with i915 blacklisted) and loading it afterwards.