1 =========================
2 OMAP2/3 Display Subsystem
3 =========================
4
5 This is an almost total rewrite of the OMAP FB
6 (let's call it DSS1). The main differences bet
7 TV-out and multiple display support, but there
8 also.
9
10 The DSS2 driver (omapdss module) is in arch/ar
11 panel and controller drivers are in drivers/vi
12 currently side by side, you can choose which o
13
14 Features
15 --------
16
17 Working and tested features include:
18
19 - MIPI DPI (parallel) output
20 - MIPI DSI output in command mode
21 - MIPI DBI (RFBI) output
22 - SDI output
23 - TV output
24 - All pieces can be compiled as a module or in
25 - Use DISPC to update any of the outputs
26 - Use CPU to update RFBI or DSI output
27 - OMAP DISPC planes
28 - RGB16, RGB24 packed, RGB24 unpacked
29 - YUV2, UYVY
30 - Scaling
31 - Adjusting DSS FCK to find a good pixel clock
32 - Use DSI DPLL to create DSS FCK
33
34 Tested boards include:
35 - OMAP3 SDP board
36 - Beagle board
37 - N810
38
39 omapdss driver
40 --------------
41
42 The DSS driver does not itself have any suppor
43 such like the current ones, but it has an inte
44 drivers can use.
45
46 The DSS driver models OMAP's overlays, overlay
47 flexible way to enable non-common multi-displa
48 modelling the hardware overlays, omapdss suppo
49 managers. These can be used when updating a di
50
51 omapdss driver support for audio
52 --------------------------------
53 There exist several display technologies and s
54 well. Hence, it is relevant to update the DSS
55 interface that may be used by an audio driver
56 the functionality.
57
58 The audio_enable function is intended to prepa
59 IP for playback (e.g., enabling an audio FIFO,
60 some IP, enabling companion chips, etc). It is
61 audio_start. The audio_disable function perfor
62 intended to be called after audio_stop.
63
64 While a given DSS device driver may support au
65 certain configurations audio is not supported
66 VESA video timing). The audio_supported functi
67 the current configuration of the display suppo
68
69 The audio_config function is intended to confi
70 parameters of the display. In order to make th
71 specific DSS device driver, a struct omap_dss_
72 is to contain all the required parameters for
73 moment, such structure contains pointers to IE
74 and CEA-861 audio infoframe structures. This s
75 HDMI and DisplayPort, as both are based on CEA
76
77 The audio_enable/disable, audio_config and aud
78 implemented as functions that may sleep. Hence
79 while holding a spinlock or a readlock.
80
81 The audio_start/audio_stop function is intende
82 playback after the configuration has taken pla
83 to be used in an atomic context. Hence, audio_
84 called only after all the needed resources for
85 DMA channels, companion chips, etc) have been
86 audio_stop is designed to only stop the audio
87 for playback are released using audio_disable.
88
89 The enum omap_dss_audio_state may be used to h
90 the interface to keep track of the audio state
91 then, the state transitions to _CONFIGURED, an
92 play audio, to _ENABLED. The state _PLAYING is
93 rendered.
94
95
96 Panel and controller drivers
97 ----------------------------
98
99 The drivers implement panel or controller spec
100 usually visible to users except through omapfb
101 themselves to the DSS driver.
102
103 omapfb driver
104 -------------
105
106 The omapfb driver implements arbitrary number
107 These framebuffers can be routed flexibly to a
108 dynamic display architecture.
109
110 The driver exports some omapfb specific ioctls
111 ioctls in the old driver.
112
113 The rest of the non standard features are expo
114 implementation will use sysfs, or ioctls, is s
115
116 V4L2 drivers
117 ------------
118
119 V4L2 is being implemented in TI.
120
121 From omapdss point of view the V4L2 drivers sh
122 driver.
123
124 Architecture
125 --------------------
126
127 Some clarification what the different componen
128
129 - Framebuffer is a memory area inside OMAP
130 pixel data for the image. Framebuffer ha
131 depth.
132 - Overlay defines where the pixels are rea
133 screen. The overlay may be smaller than
134 part of the framebuffer. The position of
135 the overlay is smaller than the display.
136 - Overlay manager combines the overlays in
137 display.
138 - Display is the actual physical display d
139
140 A framebuffer can be connected to multiple ove
141 on all of the overlays. Note that in this case
142 the same, but, in case of video overlays, the
143 framebuffer can be connected to any overlay.
144
145 An overlay can be connected to one overlay man
146 connected only to DISPC overlay managers, and
147 connected to virtual overlays.
148
149 An overlay manager can be connected to one dis
150 restrictions which kinds of displays an overla
151
152 - DISPC TV overlay manager can be only con
153 - Virtual overlay managers can only be con
154 - DISPC LCD overlay manager can be connect
155 display.
156
157 Sysfs
158 -----
159 The sysfs interface is mainly used for testing
160 interface is the best for this in the final ve
161 what would be the best interfaces for these th
162
163 The sysfs interface is divided to two parts: D
164
165 /sys/class/graphics/fb? directory:
166 mirror 0=off, 1=on
167 rotate Rotation 0-3 for 0, 90, 180, 2
168 rotate_type 0 = DMA rotation, 1 = VRFB rot
169 overlays List of overlay numbers to whi
170 phys_addr Physical address of the frameb
171 virt_addr Virtual address of the framebu
172 size Size of the framebuffer
173
174 /sys/devices/platform/omapdss/overlay? directo
175 enabled 0=off, 1=on
176 input_size width,height (ie. the framebuf
177 manager Destination overlay manager na
178 name
179 output_size width,height
180 position x,y
181 screen_width width
182 global_alpha global alpha 0-255 0=transpare
183
184 /sys/devices/platform/omapdss/manager? directo
185 display Destination di
186 name
187 alpha_blending_enabled 0=off, 1=on
188 trans_key_enabled 0=off, 1=on
189 trans_key_type gfx-destinatio
190 trans_key_value transparency c
191 default_color default backgr
192
193 /sys/devices/platform/omapdss/display? directo
194
195 =============== ==============================
196 ctrl_name Controller name
197 mirror 0=off, 1=on
198 update_mode 0=off, 1=auto, 2=manual
199 enabled 0=off, 1=on
200 name
201 rotate Rotation 0-3 for 0, 90, 180, 2
202 timings Display timings (pixclock,xres
203 When writing, two special timi
204 "pal" and "ntsc"
205 panel_name
206 tear_elim Tearing elimination 0=off, 1=o
207 output_type Output type (video encoder onl
208 =============== ==============================
209
210 There are also some debugfs files at <debugfs>
211 about clocks and registers.
212
213 Examples
214 --------
215
216 The following definitions have been made for t
217
218 ovl0=/sys/devices/platform/omapdss/ove
219 ovl1=/sys/devices/platform/omapdss/ove
220 ovl2=/sys/devices/platform/omapdss/ove
221
222 mgr0=/sys/devices/platform/omapdss/man
223 mgr1=/sys/devices/platform/omapdss/man
224
225 lcd=/sys/devices/platform/omapdss/disp
226 dvi=/sys/devices/platform/omapdss/disp
227 tv=/sys/devices/platform/omapdss/displ
228
229 fb0=/sys/class/graphics/fb0
230 fb1=/sys/class/graphics/fb1
231 fb2=/sys/class/graphics/fb2
232
233 Default setup on OMAP3 SDP
234 --------------------------
235
236 Here's the default setup on OMAP3 SDP board. A
237 and TV-out are not in use. The columns from le
238 framebuffers, overlays, overlay managers, disp
239 handled by omapfb, and the rest by the DSS::
240
241 FB0 --- GFX -\ DVI
242 FB1 --- VID1 --+- LCD ---- LCD
243 FB2 --- VID2 -/ TV ----- TV
244
245 Example: Switch from LCD to DVI
246 -------------------------------
247
248 ::
249
250 w=`cat $dvi/timings | cut -d "," -f 2
251 h=`cat $dvi/timings | cut -d "," -f 3
252
253 echo "0" > $lcd/enabled
254 echo "" > $mgr0/display
255 fbset -fb /dev/fb0 -xres $w -yres $h -
256 # at this point you have to switch the
257 echo "dvi" > $mgr0/display
258 echo "1" > $dvi/enabled
259
260 After this the configuration looks like:::
261
262 FB0 --- GFX -\ -- DVI
263 FB1 --- VID1 --+- LCD -/ LCD
264 FB2 --- VID2 -/ TV ----- TV
265
266 Example: Clone GFX overlay to LCD and TV
267 ----------------------------------------
268
269 ::
270
271 w=`cat $tv/timings | cut -d "," -f 2 |
272 h=`cat $tv/timings | cut -d "," -f 3 |
273
274 echo "0" > $ovl0/enabled
275 echo "0" > $ovl1/enabled
276
277 echo "" > $fb1/overlays
278 echo "0,1" > $fb0/overlays
279
280 echo "$w,$h" > $ovl1/output_size
281 echo "tv" > $ovl1/manager
282
283 echo "1" > $ovl0/enabled
284 echo "1" > $ovl1/enabled
285
286 echo "1" > $tv/enabled
287
288 After this the configuration looks like (only
289
290 FB0 +-- GFX ---- LCD ---- LCD
291 \- VID1 ---- TV ---- TV
292
293 Misc notes
294 ----------
295
296 OMAP FB allocates the framebuffer memory using
297 can enable Contiguous Memory Allocator (CONFIG
298 allocator, and if CMA is enabled, you use "cma
299 the global memory area for CMA.
300
301 Using DSI DPLL to generate pixel clock it is p
302 of 86.5MHz (max possible), and with that you g
303
304 Rotation and mirroring currently only supports
305 does not support mirroring.
306
307 VRFB rotation requires much more memory than n
308 probably need to increase your vram setting be
309 many applications may not work with VRFB if th
310 framebuffer parameters.
311
312 Kernel boot arguments
313 ---------------------
314
315 omapfb.mode=<display>:<mode>[,...]
316 - Default video mode for specified dis
317 "dvi:800x400MR-24@60". See drivers/
318 There are also two special modes: "p
319 can be used to tv out.
320
321 omapfb.vram=<fbnum>:<size>[@<physaddr>][,...]
322 - VRAM allocated for a framebuffer. No
323 depending on the display size. With
324 more or define the physical address
325 "1:4M" to allocate 4M for fb1.
326
327 omapfb.debug=<y|n>
328 - Enable debug printing. You have to h
329 in kernel config.
330
331 omapfb.test=<y|n>
332 - Draw test pattern to framebuffer whe
333 You need to have OMAPFB debug suppor
334
335 omapfb.vrfb=<y|n>
336 - Use VRFB rotation for all framebuffe
337
338 omapfb.rotate=<angle>
339 - Default rotation applied to all fram
340 0 - 0 degree rotation
341 1 - 90 degree rotation
342 2 - 180 degree rotation
343 3 - 270 degree rotation
344
345 omapfb.mirror=<y|n>
346 - Default mirror for all framebuffers.
347
348 omapdss.def_disp=<display>
349 - Name of default display, to which al
350 Common examples are "lcd" or "tv".
351
352 omapdss.debug=<y|n>
353 - Enable debug printing. You have to h
354 kernel config.
355
356 TODO
357 ----
358
359 DSS locking
360
361 Error checking
362
363 - Lots of checks are missing or implemented ju
364
365 System DMA update for DSI
366
367 - Can be used for RGB16 and RGB24P modes. Prob
368 to skip the empty byte?)
369
370 OMAP1 support
371
372 - Not sure if needed
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