OMAP: DSS2: Documentation for DSS2
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>
This commit is contained in:
Tomi Valkeinen
parent
640f9ca5fd
commit
4d1a7c122a
|
|
@ -0,0 +1,317 @@
|
|||
OMAP2/3 Display Subsystem
|
||||
-------------------------
|
||||
|
||||
This is an almost total rewrite of the OMAP FB driver in drivers/video/omap
|
||||
(let's call it DSS1). The main differences between DSS1 and DSS2 are DSI,
|
||||
TV-out and multiple display support, but there are lots of small improvements
|
||||
also.
|
||||
|
||||
The DSS2 driver (omapdss module) is in arch/arm/plat-omap/dss/, and the FB,
|
||||
panel and controller drivers are in drivers/video/omap2/. DSS1 and DSS2 live
|
||||
currently side by side, you can choose which one to use.
|
||||
|
||||
Features
|
||||
--------
|
||||
|
||||
Working and tested features include:
|
||||
|
||||
- MIPI DPI (parallel) output
|
||||
- MIPI DSI output in command mode
|
||||
- MIPI DBI (RFBI) output
|
||||
- SDI output
|
||||
- TV output
|
||||
- All pieces can be compiled as a module or inside kernel
|
||||
- Use DISPC to update any of the outputs
|
||||
- Use CPU to update RFBI or DSI output
|
||||
- OMAP DISPC planes
|
||||
- RGB16, RGB24 packed, RGB24 unpacked
|
||||
- YUV2, UYVY
|
||||
- Scaling
|
||||
- Adjusting DSS FCK to find a good pixel clock
|
||||
- Use DSI DPLL to create DSS FCK
|
||||
|
||||
Tested boards include:
|
||||
- OMAP3 SDP board
|
||||
- Beagle board
|
||||
- N810
|
||||
|
||||
omapdss driver
|
||||
--------------
|
||||
|
||||
The DSS driver does not itself have any support for Linux framebuffer, V4L or
|
||||
such like the current ones, but it has an internal kernel API that upper level
|
||||
drivers can use.
|
||||
|
||||
The DSS driver models OMAP's overlays, overlay managers and displays in a
|
||||
flexible way to enable non-common multi-display configuration. In addition to
|
||||
modelling the hardware overlays, omapdss supports virtual overlays and overlay
|
||||
managers. These can be used when updating a display with CPU or system DMA.
|
||||
|
||||
Panel and controller drivers
|
||||
----------------------------
|
||||
|
||||
The drivers implement panel or controller specific functionality and are not
|
||||
usually visible to users except through omapfb driver. They register
|
||||
themselves to the DSS driver.
|
||||
|
||||
omapfb driver
|
||||
-------------
|
||||
|
||||
The omapfb driver implements arbitrary number of standard linux framebuffers.
|
||||
These framebuffers can be routed flexibly to any overlays, thus allowing very
|
||||
dynamic display architecture.
|
||||
|
||||
The driver exports some omapfb specific ioctls, which are compatible with the
|
||||
ioctls in the old driver.
|
||||
|
||||
The rest of the non standard features are exported via sysfs. Whether the final
|
||||
implementation will use sysfs, or ioctls, is still open.
|
||||
|
||||
V4L2 drivers
|
||||
------------
|
||||
|
||||
V4L2 is being implemented in TI.
|
||||
|
||||
From omapdss point of view the V4L2 drivers should be similar to framebuffer
|
||||
driver.
|
||||
|
||||
Architecture
|
||||
--------------------
|
||||
|
||||
Some clarification what the different components do:
|
||||
|
||||
- Framebuffer is a memory area inside OMAP's SRAM/SDRAM that contains the
|
||||
pixel data for the image. Framebuffer has width and height and color
|
||||
depth.
|
||||
- Overlay defines where the pixels are read from and where they go on the
|
||||
screen. The overlay may be smaller than framebuffer, thus displaying only
|
||||
part of the framebuffer. The position of the overlay may be changed if
|
||||
the overlay is smaller than the display.
|
||||
- Overlay manager combines the overlays in to one image and feeds them to
|
||||
display.
|
||||
- Display is the actual physical display device.
|
||||
|
||||
A framebuffer can be connected to multiple overlays to show the same pixel data
|
||||
on all of the overlays. Note that in this case the overlay input sizes must be
|
||||
the same, but, in case of video overlays, the output size can be different. Any
|
||||
framebuffer can be connected to any overlay.
|
||||
|
||||
An overlay can be connected to one overlay manager. Also DISPC overlays can be
|
||||
connected only to DISPC overlay managers, and virtual overlays can be only
|
||||
connected to virtual overlays.
|
||||
|
||||
An overlay manager can be connected to one display. There are certain
|
||||
restrictions which kinds of displays an overlay manager can be connected:
|
||||
|
||||
- DISPC TV overlay manager can be only connected to TV display.
|
||||
- Virtual overlay managers can only be connected to DBI or DSI displays.
|
||||
- DISPC LCD overlay manager can be connected to all displays, except TV
|
||||
display.
|
||||
|
||||
Sysfs
|
||||
-----
|
||||
The sysfs interface is mainly used for testing. I don't think sysfs
|
||||
interface is the best for this in the final version, but I don't quite know
|
||||
what would be the best interfaces for these things.
|
||||
|
||||
The sysfs interface is divided to two parts: DSS and FB.
|
||||
|
||||
/sys/class/graphics/fb? directory:
|
||||
mirror 0=off, 1=on
|
||||
rotate Rotation 0-3 for 0, 90, 180, 270 degrees
|
||||
rotate_type 0 = DMA rotation, 1 = VRFB rotation
|
||||
overlays List of overlay numbers to which framebuffer pixels go
|
||||
phys_addr Physical address of the framebuffer
|
||||
virt_addr Virtual address of the framebuffer
|
||||
size Size of the framebuffer
|
||||
|
||||
/sys/devices/platform/omapdss/overlay? directory:
|
||||
enabled 0=off, 1=on
|
||||
input_size width,height (ie. the framebuffer size)
|
||||
manager Destination overlay manager name
|
||||
name
|
||||
output_size width,height
|
||||
position x,y
|
||||
screen_width width
|
||||
global_alpha global alpha 0-255 0=transparent 255=opaque
|
||||
|
||||
/sys/devices/platform/omapdss/manager? directory:
|
||||
display Destination display
|
||||
name
|
||||
alpha_blending_enabled 0=off, 1=on
|
||||
trans_key_enabled 0=off, 1=on
|
||||
trans_key_type gfx-destination, video-source
|
||||
trans_key_value transparency color key (RGB24)
|
||||
default_color default background color (RGB24)
|
||||
|
||||
/sys/devices/platform/omapdss/display? directory:
|
||||
ctrl_name Controller name
|
||||
mirror 0=off, 1=on
|
||||
update_mode 0=off, 1=auto, 2=manual
|
||||
enabled 0=off, 1=on
|
||||
name
|
||||
rotate Rotation 0-3 for 0, 90, 180, 270 degrees
|
||||
timings Display timings (pixclock,xres/hfp/hbp/hsw,yres/vfp/vbp/vsw)
|
||||
When writing, two special timings are accepted for tv-out:
|
||||
"pal" and "ntsc"
|
||||
panel_name
|
||||
tear_elim Tearing elimination 0=off, 1=on
|
||||
|
||||
There are also some debugfs files at <debugfs>/omapdss/ which show information
|
||||
about clocks and registers.
|
||||
|
||||
Examples
|
||||
--------
|
||||
|
||||
The following definitions have been made for the examples below:
|
||||
|
||||
ovl0=/sys/devices/platform/omapdss/overlay0
|
||||
ovl1=/sys/devices/platform/omapdss/overlay1
|
||||
ovl2=/sys/devices/platform/omapdss/overlay2
|
||||
|
||||
mgr0=/sys/devices/platform/omapdss/manager0
|
||||
mgr1=/sys/devices/platform/omapdss/manager1
|
||||
|
||||
lcd=/sys/devices/platform/omapdss/display0
|
||||
dvi=/sys/devices/platform/omapdss/display1
|
||||
tv=/sys/devices/platform/omapdss/display2
|
||||
|
||||
fb0=/sys/class/graphics/fb0
|
||||
fb1=/sys/class/graphics/fb1
|
||||
fb2=/sys/class/graphics/fb2
|
||||
|
||||
Default setup on OMAP3 SDP
|
||||
--------------------------
|
||||
|
||||
Here's the default setup on OMAP3 SDP board. All planes go to LCD. DVI
|
||||
and TV-out are not in use. The columns from left to right are:
|
||||
framebuffers, overlays, overlay managers, displays. Framebuffers are
|
||||
handled by omapfb, and the rest by the DSS.
|
||||
|
||||
FB0 --- GFX -\ DVI
|
||||
FB1 --- VID1 --+- LCD ---- LCD
|
||||
FB2 --- VID2 -/ TV ----- TV
|
||||
|
||||
Example: Switch from LCD to DVI
|
||||
----------------------
|
||||
|
||||
w=`cat $dvi/timings | cut -d "," -f 2 | cut -d "/" -f 1`
|
||||
h=`cat $dvi/timings | cut -d "," -f 3 | cut -d "/" -f 1`
|
||||
|
||||
echo "0" > $lcd/enabled
|
||||
echo "" > $mgr0/display
|
||||
fbset -fb /dev/fb0 -xres $w -yres $h -vxres $w -vyres $h
|
||||
# at this point you have to switch the dvi/lcd dip-switch from the omap board
|
||||
echo "dvi" > $mgr0/display
|
||||
echo "1" > $dvi/enabled
|
||||
|
||||
After this the configuration looks like:
|
||||
|
||||
FB0 --- GFX -\ -- DVI
|
||||
FB1 --- VID1 --+- LCD -/ LCD
|
||||
FB2 --- VID2 -/ TV ----- TV
|
||||
|
||||
Example: Clone GFX overlay to LCD and TV
|
||||
-------------------------------
|
||||
|
||||
w=`cat $tv/timings | cut -d "," -f 2 | cut -d "/" -f 1`
|
||||
h=`cat $tv/timings | cut -d "," -f 3 | cut -d "/" -f 1`
|
||||
|
||||
echo "0" > $ovl0/enabled
|
||||
echo "0" > $ovl1/enabled
|
||||
|
||||
echo "" > $fb1/overlays
|
||||
echo "0,1" > $fb0/overlays
|
||||
|
||||
echo "$w,$h" > $ovl1/output_size
|
||||
echo "tv" > $ovl1/manager
|
||||
|
||||
echo "1" > $ovl0/enabled
|
||||
echo "1" > $ovl1/enabled
|
||||
|
||||
echo "1" > $tv/enabled
|
||||
|
||||
After this the configuration looks like (only relevant parts shown):
|
||||
|
||||
FB0 +-- GFX ---- LCD ---- LCD
|
||||
\- VID1 ---- TV ---- TV
|
||||
|
||||
Misc notes
|
||||
----------
|
||||
|
||||
OMAP FB allocates the framebuffer memory using the OMAP VRAM allocator.
|
||||
|
||||
Using DSI DPLL to generate pixel clock it is possible produce the pixel clock
|
||||
of 86.5MHz (max possible), and with that you get 1280x1024@57 output from DVI.
|
||||
|
||||
Rotation and mirroring currently only supports RGB565 and RGB8888 modes. VRFB
|
||||
does not support mirroring.
|
||||
|
||||
VRFB rotation requires much more memory than non-rotated framebuffer, so you
|
||||
probably need to increase your vram setting before using VRFB rotation. Also,
|
||||
many applications may not work with VRFB if they do not pay attention to all
|
||||
framebuffer parameters.
|
||||
|
||||
Kernel boot arguments
|
||||
---------------------
|
||||
|
||||
vram=<size>
|
||||
- Amount of total VRAM to preallocate. For example, "10M". omapfb
|
||||
allocates memory for framebuffers from VRAM.
|
||||
|
||||
omapfb.mode=<display>:<mode>[,...]
|
||||
- Default video mode for specified displays. For example,
|
||||
"dvi:800x400MR-24@60". See drivers/video/modedb.c.
|
||||
There are also two special modes: "pal" and "ntsc" that
|
||||
can be used to tv out.
|
||||
|
||||
omapfb.vram=<fbnum>:<size>[@<physaddr>][,...]
|
||||
- VRAM allocated for a framebuffer. Normally omapfb allocates vram
|
||||
depending on the display size. With this you can manually allocate
|
||||
more or define the physical address of each framebuffer. For example,
|
||||
"1:4M" to allocate 4M for fb1.
|
||||
|
||||
omapfb.debug=<y|n>
|
||||
- Enable debug printing. You have to have OMAPFB debug support enabled
|
||||
in kernel config.
|
||||
|
||||
omapfb.test=<y|n>
|
||||
- Draw test pattern to framebuffer whenever framebuffer settings change.
|
||||
You need to have OMAPFB debug support enabled in kernel config.
|
||||
|
||||
omapfb.vrfb=<y|n>
|
||||
- Use VRFB rotation for all framebuffers.
|
||||
|
||||
omapfb.rotate=<angle>
|
||||
- Default rotation applied to all framebuffers.
|
||||
0 - 0 degree rotation
|
||||
1 - 90 degree rotation
|
||||
2 - 180 degree rotation
|
||||
3 - 270 degree rotation
|
||||
|
||||
omapfb.mirror=<y|n>
|
||||
- Default mirror for all framebuffers. Only works with DMA rotation.
|
||||
|
||||
omapdss.def_disp=<display>
|
||||
- Name of default display, to which all overlays will be connected.
|
||||
Common examples are "lcd" or "tv".
|
||||
|
||||
omapdss.debug=<y|n>
|
||||
- Enable debug printing. You have to have DSS debug support enabled in
|
||||
kernel config.
|
||||
|
||||
TODO
|
||||
----
|
||||
|
||||
DSS locking
|
||||
|
||||
Error checking
|
||||
- Lots of checks are missing or implemented just as BUG()
|
||||
|
||||
System DMA update for DSI
|
||||
- Can be used for RGB16 and RGB24P modes. Probably not for RGB24U (how
|
||||
to skip the empty byte?)
|
||||
|
||||
OMAP1 support
|
||||
- Not sure if needed
|
||||
|
||||
Loading…
Reference in New Issue