XO 4 HDMI Debug
Some notes for testing the HDMI Interface of the XO-4 laptop.
Contents
Setup
If you have access to Q7B05 or later, you can install it on the test laptop and avoid the older setup which required Linux involvement to setup HDMI.
Older Setup
Start with an XO-4 laptop running the latest firmware ( Q7B04 ). It should have a second serial port connected. You will want to download the following two pieces of software and place them on a USB stick:
Install the zImage file as /boot/vmlinuz using the following OFW command:
ok copy u:\zImhdmi int:\boot\vmlinuz
Type y when it asks if it is OK to overwrite the existing file.
Boot Linux. Then mount the USB key and install hdmi_ctl into the local directory:
mount /dev/sda1 /mnt cp /mnt/hdmi_ctl . chmod a+x hdmi_ctl
Video Init
If using OFW q7b05 or later, you can initialize the HDMI output using one of the following three commands:
ok> 720p ok> 1080p ok> d# 640 d# 480 " start-hdmi" $call-screen
A list of the supported resolutions is available in the OFW source code.
Using Linux
At this point, you can initialize HDMI output from within Linux:
./hdmi_ctl
When this starts, you can set video output at a particular resolution using:
>> sv 14
That will select 720p on your HDMI monitor. "sv 24" will get you 1080p, "sv 25" will get 640x480.
Patching CForth
In order to manipulate the video parameters in real time, we use a second serial port connected to CForth running on the security processor. It must be enabled by holding down the "rotate" key while booting. Then start ofw using the command:
ok dbg ofw
The following forth commands need to be downloaded (over the second serial port):
: w1 20b000 + io! ; : r1 20b000 + io@ ; : video-on 104 r1 44 w1 fc r1 3c w1 f4 r1 34 w1 80 r1 100 or 80 w1 ; alias v video-on : +hdmi 20bc00 + ; : hdmi! +hdmi io! ; : hdmi@ +hdmi io@ ; : hdmi-i! ( b reg# -- ) swap 0 hdmi! h# 8000.0000 or 4 hdmi! ; : hdmi-i@ ( reg# -- b ) h# 4000.0000 or 4 hdmi! 0 hdmi@ ; alias r hdmi@ alias w hdmi! alias ii hdmi-i! alias ir hdmi-i@ : access-phy h# 20 hdmi@ 1 or h# 20 hdmi! ; alias phy access-phy : access-3d h# 20 hdmi@ 1 invert and h# 20 hdmi! ; alias 3d access-3d
And these allow for easier manipulation of the PHY0 and PHY1 registers:
6 value damp 5 value eamp 2 value cp : phy0 damp o# 1111 * eamp o# 11110000 * or cp h# 55000000 * or 8 w ; 0 value ajd 1 value svtx 9 value idrv : phy1 ajd h# f0000000 * svtx o# 1111 * d# 16 lshift or idrv h# 1111 * or h# c w ;
These will need to be downloaded again after turning the laptop off.
You can use these patches to manipulate the PHY registers by typing:
phy phy0 phy1
Display some video using
v
Changing PHY Settings
You must rerun CForth register settings after using hdmi_ctl, 720p, or 1080p. After changing the resolution with hdmi_ctl, you must re-run:
phy phy0 phy1
In order to change a value, change the associated variable and then re-write the related register. To change DAMP to 3:
3 to damp phy0
To change IDRV to 4:
4 to idrv phy1
Note: There is hysteresis in the PHY circuit. Once you pass a certain threshold, you can't return simply by reducing the value. If you are close to a critical point, increasing a parameter by 1 may result in a change such that then reducing that parameter by 1 doesn't restore us to the same output. In many cases, the parameter must be reduced by 3 then increased by 2 o restore the same output.
