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Documentation / fb / ep93xx-fb.txt




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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

1	================================
2	Driver for EP93xx LCD controller
3	================================
4	
5	The EP93xx LCD controller can drive both standard desktop monitors and
6	embedded LCD displays. If you have a standard desktop monitor then you
7	can use the standard Linux video mode database. In your board file:
8	
9		static struct ep93xxfb_mach_info some_board_fb_info = {
10			.num_modes	= EP93XXFB_USE_MODEDB,
11			.bpp		= 16,
12		};
13	
14	If you have an embedded LCD display then you need to define a video
15	mode for it as follows:
16	
17		static struct fb_videomode some_board_video_modes[] = {
18			{
19				.name		= "some_lcd_name",
20				/* Pixel clock, porches, etc */
21			},
22		};
23	
24	Note that the pixel clock value is in pico-seconds. You can use the
25	KHZ2PICOS macro to convert the pixel clock value. Most other values
26	are in pixel clocks. See Documentation/fb/framebuffer.txt for further
27	details.
28	
29	The ep93xxfb_mach_info structure for your board should look like the
30	following:
31	
32		static struct ep93xxfb_mach_info some_board_fb_info = {
33			.num_modes	= ARRAY_SIZE(some_board_video_modes),
34			.modes		= some_board_video_modes,
35			.default_mode	= &some_board_video_modes[0],
36			.bpp		= 16,
37		};
38	
39	The framebuffer device can be registered by adding the following to
40	your board initialisation function:
41	
42		ep93xx_register_fb(&some_board_fb_info);
43	
44	=====================
45	Video Attribute Flags
46	=====================
47	
48	The ep93xxfb_mach_info structure has a flags field which can be used
49	to configure the controller. The video attributes flags are fully
50	documented in section 7 of the EP93xx users' guide. The following
51	flags are available:
52	
53	EP93XXFB_PCLK_FALLING		Clock data on the falling edge of the
54					pixel clock. The default is to clock
55					data on the rising edge.
56	
57	EP93XXFB_SYNC_BLANK_HIGH	Blank signal is active high. By
58					default the blank signal is active low.
59	
60	EP93XXFB_SYNC_HORIZ_HIGH	Horizontal sync is active high. By
61					default the horizontal sync is active low.
62	
63	EP93XXFB_SYNC_VERT_HIGH		Vertical sync is active high. By
64					default the vertical sync is active high.
65	
66	The physical address of the framebuffer can be controlled using the
67	following flags:
68	
69	EP93XXFB_USE_SDCSN0		Use SDCSn[0] for the framebuffer. This
70					is the default setting.
71	
72	EP93XXFB_USE_SDCSN1		Use SDCSn[1] for the framebuffer.
73	
74	EP93XXFB_USE_SDCSN2		Use SDCSn[2] for the framebuffer.
75	
76	EP93XXFB_USE_SDCSN3		Use SDCSn[3] for the framebuffer.
77	
78	==================
79	Platform callbacks
80	==================
81	
82	The EP93xx framebuffer driver supports three optional platform
83	callbacks: setup, teardown and blank. The setup and teardown functions
84	are called when the framebuffer driver is installed and removed
85	respectively. The blank function is called whenever the display is
86	blanked or unblanked.
87	
88	The setup and teardown devices pass the platform_device structure as
89	an argument. The fb_info and ep93xxfb_mach_info structures can be
90	obtained as follows:
91	
92		static int some_board_fb_setup(struct platform_device *pdev)
93		{
94			struct ep93xxfb_mach_info *mach_info = pdev->dev.platform_data;
95			struct fb_info *fb_info = platform_get_drvdata(pdev);
96	
97			/* Board specific framebuffer setup */
98		}
99	
100	======================
101	Setting the video mode
102	======================
103	
104	The video mode is set using the following syntax:
105	
106		video=XRESxYRES[-BPP][@REFRESH]
107	
108	If the EP93xx video driver is built-in then the video mode is set on
109	the Linux kernel command line, for example:
110	
111		video=ep93xx-fb:800x600-16@60
112	
113	If the EP93xx video driver is built as a module then the video mode is
114	set when the module is installed:
115	
116		modprobe ep93xx-fb video=320x240
117	
118	==============
119	Screenpage bug
120	==============
121	
122	At least on the EP9315 there is a silicon bug which causes bit 27 of
123	the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is
124	an unofficial errata for this bug at:
125		http://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2
126	
127	By default the EP93xx framebuffer driver checks if the allocated physical
128	address has bit 27 set. If it does, then the memory is freed and an
129	error is returned. The check can be disabled by adding the following
130	option when loading the driver:
131	
132	      ep93xx-fb.check_screenpage_bug=0
133	
134	In some cases it may be possible to reconfigure your SDRAM layout to
135	avoid this bug. See section 13 of the EP93xx users' guide for details.
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