u-boot/doc/README.video
Hans de Goede 7fad8a9802 sunxi: video: Add a hpd_delay parameter to configure hpd delay
In some extreme cases it may be necessary to wait 1.5 seconds or more for a hpd
signal to show up (and be able to read edid info), but we do not want to
penalize all headless boots with an extra second boot delay, so add a hpd_delay
parameter which can be set through the video-mode env. variable.

While at it raise the default from 300ms to 500ms as 300 may very well be too
low in many cases.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
2015-01-14 14:56:39 +01:00

70 lines
2.6 KiB
Text

/*
* (C) Copyright 2000
* Paolo Scaffardi, AIRVENT SAM s.p.a - RIMINI(ITALY), arsenio@tin.it
*
* SPDX-License-Identifier: GPL-2.0+
*/
"video-mode" environment variable
=================================
The 'video-mode' environment variable can be used to enable and configure
some video drivers. The format matches the video= command-line option used
for Linux:
video-mode=<driver>:<xres>x<yres>-<depth>@<freq><,option=string>
<driver> The video driver name, ignored by U-Boot
<xres> The X resolution (in pixels) to use.
<yres> The Y resolution (in pixels) to use.
<depth> The color depth (in bits) to use.
<freq> The frequency (in Hz) to use.
<options> A comma-separated list of device-specific options
U-Boot MPC8xx video controller driver
=====================================
The driver has been tested with the following configurations:
- MPC823FADS with AD7176 on a PAL TV (YCbYCr) - arsenio@tin.it
Example: video-mode=fslfb:1280x1024-32@60,monitor=dvi
U-boot sunxi video controller driver
====================================
U-boot supports hdmi and lcd output on Allwinner sunxi SoCs, lcd output
requires the CONFIG_VIDEO_LCD_MODE Kconfig value to be set.
The sunxi u-boot driver supports the following video-mode options:
- monitor=[none|dvi|hdmi|lcd] - Select the video output to use
none: Disable video output.
dvi/hdmi: Selects output over the hdmi connector with dvi resp. hdmi output
format, if edid is used the format is automatically selected.
lcd: Selects video output to a LCD screen.
vga: Selects bideo output over the VGA connector.
Defaults to monitor=dvi.
- hpd=[0|1] - Enable use of the hdmi HotPlug Detect feature
0: Disabled. Configure dvi/hdmi output even if no cable is detected
1: Enabled. Fallback to the lcd / vga / none in that order (if available)
Defaults to hpd=1.
- hpd_delay=<int> - How long to wait for the hdmi HPD signal in milliseconds
When the monitor and the board power up at the same time, it may take some
time for the monitor to assert the HPD signal. This configures how long to
wait for the HPD signal before assuming no cable is connected.
Defaults to hpd_delay=500.
- edid=[0|1] - Enable use of DDC + EDID to get monitor info
0: Disabled.
1: Enabled. If valid EDID info was read from the monitor the EDID info will
overrides the xres, yres and refresh from the video-mode env. variable.
Defaults to edid=1.
For example to always use the hdmi connector, even if no cable is inserted,
using edid info when available and otherwise initalizing it at 1024x768@60Hz,
use: "setenv video-mode sunxi:1024x768-24@60,monitor=dvi,hpd=0,edid=1".