xref: /openbmc/linux/Documentation/fb/intelfb.rst (revision da1d9caf)
1=============================================================
2Intel 830M/845G/852GM/855GM/865G/915G/945G Framebuffer driver
3=============================================================
4
5A. Introduction
6===============
7
8This is a framebuffer driver for various Intel 8xx/9xx compatible
9graphics devices.  These would include:
10
11	- Intel 830M
12	- Intel 845G
13	- Intel 852GM
14	- Intel 855GM
15	- Intel 865G
16	- Intel 915G
17	- Intel 915GM
18	- Intel 945G
19	- Intel 945GM
20	- Intel 945GME
21	- Intel 965G
22	- Intel 965GM
23
24B.  List of available options
25=============================
26
27   a. "video=intelfb"
28	enables the intelfb driver
29
30	Recommendation: required
31
32   b. "mode=<xres>x<yres>[-<bpp>][@<refresh>]"
33	select mode
34
35	Recommendation: user preference
36	(default = 1024x768-32@70)
37
38   c. "vram=<value>"
39	select amount of system RAM in MB to allocate for the video memory
40	if not enough RAM was already allocated by the BIOS.
41
42	Recommendation: 1 - 4 MB.
43	(default = 4 MB)
44
45   d. "voffset=<value>"
46	select at what offset in MB of the logical memory to allocate the
47	framebuffer memory.  The intent is to avoid the memory blocks
48	used by standard graphics applications (XFree86). Depending on your
49	usage, adjust the value up or down, (0 for maximum usage, 63/127 MB
50	for the least amount).  Note, an arbitrary setting may conflict
51	with XFree86.
52
53	Recommendation: do not set
54	(default = 48 MB)
55
56   e. "accel"
57	enable text acceleration.  This can be enabled/reenabled anytime
58	by using 'fbset -accel true/false'.
59
60	Recommendation: enable
61	(default = set)
62
63   f. "hwcursor"
64	enable cursor acceleration.
65
66	Recommendation: enable
67	(default = set)
68
69   g. "mtrr"
70	enable MTRR.  This allows data transfers to the framebuffer memory
71	to occur in bursts which can significantly increase performance.
72	Not very helpful with the intel chips because of 'shared memory'.
73
74	Recommendation: set
75	(default = set)
76
77   h. "fixed"
78	disable mode switching.
79
80	Recommendation: do not set
81	(default = not set)
82
83   The binary parameters can be unset with a "no" prefix, example "noaccel".
84   The default parameter (not named) is the mode.
85
86C. Kernel booting
87=================
88
89Separate each option/option-pair by commas (,) and the option from its value
90with an equals sign (=) as in the following::
91
92	video=intelfb:option1,option2=value2
93
94Sample Usage
95------------
96
97In /etc/lilo.conf, add the line::
98
99	append="video=intelfb:mode=800x600-32@75,accel,hwcursor,vram=8"
100
101This will initialize the framebuffer to 800x600 at 32bpp and 75Hz. The
102framebuffer will use 8 MB of System RAM. hw acceleration of text and cursor
103will be enabled.
104
105Remarks
106-------
107
108If setting this parameter doesn't work (you stay in a 80x25 text-mode),
109you might need to set the "vga=<mode>" parameter too - see vesafb.txt
110in this directory.
111
112
113D.  Module options
114==================
115
116The module parameters are essentially similar to the kernel
117parameters. The main difference is that you need to include a Boolean value
118(1 for TRUE, and 0 for FALSE) for those options which don't need a value.
119
120Example, to enable MTRR, include "mtrr=1".
121
122Sample Usage
123------------
124
125Using the same setup as described above, load the module like this::
126
127	modprobe intelfb mode=800x600-32@75 vram=8 accel=1 hwcursor=1
128
129Or just add the following to a configuration file in /etc/modprobe.d/::
130
131	options intelfb mode=800x600-32@75 vram=8 accel=1 hwcursor=1
132
133and just do a::
134
135	modprobe intelfb
136
137
138E.  Acknowledgment:
139===================
140
141	1.  Geert Uytterhoeven - his excellent howto and the virtual
142	    framebuffer driver code made this possible.
143
144	2.  Jeff Hartmann for his agpgart code.
145
146	3.  David Dawes for his original kernel 2.4 code.
147
148	4.  The X developers.  Insights were provided just by reading the
149	    XFree86 source code.
150
151	5.  Antonino A. Daplas for his inspiring i810fb driver.
152
153	6.  Andrew Morton for his kernel patches maintenance.
154
155Sylvain
156