Boundary Devices Nitrogen series User Manual - Page 14

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5.8 Linux display setup

5.8

Linux display setup

Our current version of U-Boot does not have display support, but it can be used to conﬁgure the

kernel's display until we get proper display support.

The lcdpanel command is currently used to deﬁne an environment variable panel that can be

used to construct the kernel command line arguments

panels shipped by Boundary Devices as well as support for Discrete Monitor Timings (dmt) and

the VESA Generalized Timing Formula.

It may be used in one of the following ways:

command string

lcdp ?

lcdp panelname

lcdp vesa:WxH@FREQ

lcdp +

lcdp name:ﬁeld,ﬁeld...

As mentioned earlier, this command does not currently conﬁgure the display adapter on the Ni-

trogen board. It simply sets the panel environment variable for use in constructing a bootargs

variable.

To rehash previous comments, the bootargs variable contains the Linux kernel command-line.

The Linux kernel display driver contains support for initializing the display adapter through the

use of the 'video=mxcfb:' kernel parameter. To enable arbitrary displays, we added support for a

raw speciﬁer that matches our previous use of the lcdpanel U-Boot command.

To complicate matters, we also added support for three I/O widths to support the physical con-

nections to two internal connectors and the HDMI adapter:

777 - 7" display connector (21-bit color)

666 - 4.3" display connector (18-bit color)

888 - HDMI output (24-bit color)

These I/O identiﬁers are added after the panel variable in a kernel command-line, separated by a

comma.

Putting all of this together, the following example shows how to set the kernel command line for

an Ubuntu Live boot with a 1024x768 panel over HDMI:

U-Boot> lcdp vesa:1024x768@60

U-Boot> set bootargs "video=$panel,888 boot=casper"

U-Boot> saveenv

To use a 7" panel in a Boundary enclosure, you can specify things like this:

U-Boot> lcdp vesa:800x480@60

U-Boot> set bootargs "video=$panel,777 boot=casper"

U-Boot> saveenv

variable bootargs

March 10, 2011

description

Show the list of currently supported lcd panels

Select and initialize a known panel by name

Select and initialize a VESA GTF panel with speciﬁed Width, Height, and FREQu

Add a new panel (prompts for all of the details)

Specify a panel name in all it's gory details

Revision 1.5

. The command contains support for most