[This file is cloned from VesaFB. Thanks go to Gerd Knorr]

what is matroxfb?
=================

This is a driver for a graphic framebuffer for Matrox devices on
Alpha, Intel and PPC boxes.

Advantages:

 * It provides a nice large console (128 cols + 48 lines with 1024x768)
   without using tiny, unreadable fonts.
 * You can run XF68_FBDev on top of /dev/fb0
 * Most important: boot logo :-)

Disadvantages:

 * graphic mode is slower than text mode... but you should not notice
   if you use same resolution as you used in textmode.


How to use it?
==============

Switching modes is done using the video=matrox:vesa=... boot parameter
or using `fbset' program.

You should compile in both vgacon (to boot if you remove you Matrox from
box) and matroxfb (for graphics mode). You should not compile-in vesafb
unless you have primary display on non-Matrox VBE2.0 device (see 
Documentation/vesafb.txt for details).

Currently supported video modes are (through vesa=... interface, PowerMac
has (as addon) compatibility code.

bpp | 640x400  640x480  768x576  800x600  960x720  1024x768 1152x864 1280x1024 1408x1056 1600x1200
----+----------------------------------------------------------------------------------------------
  4 |            0x12             0x102             0x104             0x106
  8 |  0x100    0x101    0x180    0x103    0x188    0x105    0x190    0x107     0x198     0x11C
 15 |           0x110    0x181    0x113    0x189    0x116    0x191    0x119     0x199     0x11D
 16 |           0x111    0x182    0x114    0x18A    0x117    0x192    0x11A     0x19A     0x11E
 24 |           0x1B2    0x184    0x1B5    0x18C    0x1B8    0x194    0x1BB     0x19C     0x1BF
 32 |           0x112    0x183    0x115    0x18B    0x118    0x193    0x11B     0x19B

text | 640x400  640x480  1056x344  1056x400  1056x480
-----+------------------------------------------------
 8x8 |  0x1C0    0x108     0x10A     0x10B     0x10C
8x16 | 2, 3, 7                       0x109

You can enter these number either hexadecimal (leading `0x') or decimal (0x100 = 256). You can also
use value + 512 to achieve compatibility with your old number passed to vesafb.

Non-listed number can be achieved by more complicated command-line, for example
1600x1200x32bpp can be specified by `video=matrox:vesa:0x11C,depth:32'.


X11
===

XF68_FBDev should work just fine, but it is non-accelerated. On non-intel
architectures there are some glitches for 24bpp videomodes. 8, 16 and 32bpp
works fine.

Running another (accelerated) X-Server like XF86_SVGA works too. But (at least)
XFree servers have big troubles in multihead configurations (even on first
head, not even talking about second).


SVGALib
=======

Driver contains SVGALib compatibility code. It is turned on by choosing textual
mode for console. You can do it at boottime by using videomode 2,3,7,0x108-0x10C 
or 0x1C0. At runtime, `fbset -depth 0' does this work.
Unfortunately, after SVGALib application exits, screen contents is corrupted.
Switching to another console and back fixes it. I hope that it is SVGALib and
not mine problem, but I'm not sure.


Configuration
=============

You can pass kernel command line options to vesafb with
`video=matrox:option1,option2:value2,option3' (multiple options should be 
separated by comma, values are separated from options by `:'). 
Accepted options:

mem:X    - size of memory (X can be in megabytes, kilobytes or bytes)
           You can only decrease value determined by driver because of
	   it always probe for memory. Default is to use whole detected
	   memory usable for on-screen display (i.e. max. 8MB).
disabled - do not load driver; you can use also `off', but `disabled'
           is here too.
enabled  - load driver, if you have `video=matrox:disabled' in LILO configuration,
           you can override it by this (you cannot override `off').
	   It is default.
noaccel  - do not use acceleration engine. It does not work on Alphas.
accel    - use acceleration engine. It is default.
nopan    - create initial consoles with vyres = yres, thus disabling virtual
           scrolling.
pan      - create initial consoles as tall as possible (vyres = memory/vxres).
           It is default.
nopciretry - disable PCI retries. It is needed for some broken chipsets,
           it is autodetected for intel's 82437. In this case device does
	   not comply to PCI 2.1 specs (it will not guarantee that every transaction
	   terminate with success or retry in 32 PCLK).
pciretry - enable PCI retries. It is default, except for intel's 82437.
novga    - disables VGA I/O ports. It is default if BIOS did not enable device.
           You should not use this option, some boards then do not restart without
	   power off.
vga      - preserve state of VGA I/O ports. It is default. Driver does not enable
           VGA I/O if BIOS did not it (it is not safe to enable it in most cases).
nobios   - disables BIOS ROM. It is default if BIOS did not enable BIOS itself.
           You should not use this option, some boards then do not restart without
	   power off.
bios     - preserve state of BIOS ROM. It is default. Driver does not enable BIOS
           if BIOS was not enabled before.
noinit   - tells driver, that devices were already initialized. You should use it
           if you have G100 and/or if driver cannot detect memory, you see strange
	   pattern on screen and so on. Devices not enabled by BIOS are still
	   initialized. It is default.
init     - driver initializes every device it knows about.
nomtrr   - disables write combining on frame buffer. This slows down driver but
           there is reported minor incompatibility between GUS DMA and XFree under
	   high loads if write combining is enabled (sound dropouts).
mtrr     - enables write combining on frame buffer. It speeds up video accesses
           much. It is default. You must have MTRR support enabled in kernel and
	   your CPU must have MTRR (f.e. Pentium II have them).
sgram    - tells to driver that you have G200 with SGRAM memory. It has no effect 
           without `init'.
sdram    - tells to driver that you have G200 with SDRAM memory. It is a default.
inv24    - change timings parameters for 24bpp modes on Millenium and Millenium II.
           Specify this if you see strange color shadows around characters.
noinv24  - use standard timmings. It is default.
inverse  - invert colors on screen (for LCD displays)
noinverse - show true colors on screen. It is default.
dev:X    - bind driver to device X. Driver numbers device from 0 up to N, where device
           0 is first `known' device found, 1 second and so on. lspci lists
	   devices in this order.
	   Default is `every' known device for driver with multihead support and
	   first working device (usually dev:0) for driver without multihead support.
nohwcursor - disables hardware cursor (use software cursor instead).
hwcursor - enables hardware cursor. It is default. If you are using non-accelerated mode
           (`noaccel' or `fbset -accel false'), software cursor is used (except for
	   text mode).
noblink  - disables cursor blinking. Cursor in text mode always blinks (hw limitation).
blink    - enables cursor blinking. It is default.
nofastfont - disables fastfont feature. It is default.
fastfont:X - enables fastfont feature. X specifies size of memory reserved for font data,
           it must be >= (fontwidth*fontheight*chars_in_font)/8. It is faster on
	   Gx00 series, but slower on older cards.
grayscale - enable grayscale summing. It works in PSEUDOCOLOR modes (text, 4bpp, 8bpp). In
           DIRECTCOLOR modes it is limited to characters displayed through putc/putcs. Direct
	   accesses to framebuffer can paint colors.
nograyscale - disable grayscale summing. It is default.
cross4MB - enables that pixel line can cross 4MB boundary. It is default for non-Millenium.
nocross4MB - pixel line must not cross 4MB boundary. It is default for Millenium I or II,
           because of these devices have hardware limitations which do not allow this.
	   But this option is incompatible with some (if not all yet released) versions
	   of XF86_FBDev.
vesa:X   - selects startup videomode. X is number from 0 to 0x1FF, see table above
           for detailed explanation. Default is 640x480, 8bpp if driver has 8bpp support.
	   Otherwise first available of 640x350x4bpp, 640x480x15bpp, 640x480x24bpp,
	   640x480x32bpp or 80x25 text (80x25 text is always available).
If you are not satisfied with videomode selected by `vesa' option, you
can modify it with these options:
xres:X   - horizontal resolution, in pixels. Default is derived from `vesa' option.
yres:X   - vertical resolution, in pixel lines. Default is derived from `vesa' option.
upper:X  - top boundary: lines between end of VSYNC pulse and start of first pixel line 
           of picture. Default is derived from `vesa' option.
lower:X  - bottom boundary: lines between end of picture and start of VSYNC pulse.
           Default is derived from `vesa' option.
vslen:X  - length of VSYNC pulse, in lines. Default is derived from `vesa' option.
left:X   - left boundary: pixels between end of HSYNC pulse and first pixel. Default
           is derived from `vesa' option.
right:X  - right boundary: pixels between end of picture and start of HSYNC pulse.
           Default is derived from `vesa' option.
hslen:X  - length of HSYNC pulse, in pixels. Default is derived from `vesa' option.
pixclock:X - dotclocks, in ps (picoseconds). Default is derived from `vesa' option and
           from `fh' and `fv' options.
sync:X   - sync. pulse - bit 0 inverts HSYNC polarity, bit 1 VSYNC polarity.
           If bit 3 (value 0x08) is set, composite sync instead of HSYNC is generated.
	   If bit 5 (value 0x20) is set, sync on green is turned on.
	   Default depends on `vesa'.
depth:X  - Bits per pixel: 0=text, 4,8,15,16,24 or 32. Default depends on `vesa'.
If you know capabilities of your monitor, you can specify some (or all) of `pixclk', `fh'
and `fv'. In this case, `pixclock' is computed so that pixclock <= maxclk, real_fh <= fh
and real_fv <= fv.
maxclk:X - maximum dotclock. X can be specified in MHz, kHz or Hz. Default is `don't care'.
fh:X     - maximum horizontal synchronization frequency. X can be specified in kHz or Hz.
           Default is `don't care'.
fv:X     - maximum vertical frequency. X must be specified in Hz. Default is 70 for modes
           derived from `vesa' with yres <= 400, 60Hz for yres > 400.


Limitations
===========

There are known and unknown bugs, features and misfeatures.
Currently there are following known bugs:
 + G100 support does not work as expected, I'm still investigating this one.
   Using `noinit' option works, but only for `first' head :-(
 + SVGALib does not restore screen on exit
 + generic fbcon-cfbX procedures do not work on Alphas. Due to this,
   `noaccel' (and cfb4 accel) driver does not work on Alpha. So everyone
   with access to /dev/fb* on Alpha can hang machine (you should restrict
   access to /dev/fb* - everyone with access to this device can destroy
   your monitor, believe me...).
 + 24bpp does not support correctly XF-FBDev on big-endian architectures.
 + interlaced text mode is not supported; it looks like hardware limitiation,
   but I'm not sure.
 + G200 SGRAM/SDRAM is not autodetected.
 + maybe more...
And following misfeatures:
 + SVGALib does not restore screen on exit.
 + pixclock for text modes is limited by hardware to
    83MHz on G200
    66MHz on Millenium I
    60MHz on Millenium II
   Because of I have not access to other devices, I do not know specific
   frequencies for them. So driver does not check this and allows you to
   set frequency higher that this. It cause sparks, black holes and other
   pretty effects on screen. Device was not destroyed during tests :-)
 + my Millenium G200 oscillator has frequency range from 35MHz to 380MHz
   (and it works with 8bpp on about 320MHz dotclocks (and changed mclk)).
   But Matrox says on product sheet that VCO limit is 50-250MHz, so I believe
   them (maybe that chip overheates, but it has very big cooler (G100 has
   not one), so it should work).
 + special mixed video/graphics videomodes of Mystique and Gx00 - 2G8V16 and
   G16V16 are not supported
 + color keying is not supported
 + feature connector of Mystique and Gx00 is set to VGA mode (it is disabled
   by BIOS)
 + DCC (monitor detection) protocol is not implemented
 + some check for input values are not so strict how it should be (you can
   specify vslen=4000 and so on).
 + maybe more...
And following features:
 + 4bpp is available only on Millenium I and Millenium II. It is hardware
   limitiation.
 + current fbset is not able to set 15bpp videomode: you must specify
   depth==16 and green.length==5. fbset does not allow you to set 
   green.length.
 + hardware cursor is available only in accelerated videomodes. Maybe that
   this is misfeature and not feature.
 + text mode uses 6 bit VGA palette instead of 8 bit (one of 262144 colors
   instead of one of 16M colors). It is due to hardware limitation of 
   MilleniumI/II and SVGALib compatibility.


Benchmarks
==========
It is time to redraw whole screen 1000 times in 1024x768, 60Hz. It is
time for draw 6144000 characters on screen through /dev/vcsa
(for 32bpp it is about 3GB of data (exactly 3000 MB); for 8x16 font in 
16 seconds, i.e. 187MBps).
Times were obtained from one older version of driver, now they are about 3%
faster, it is kernel-space only time on P-II/350MHz, Millenium I in 33MHz
PCI slot, G200 in AGP 2x slot. I did not test vgacon.

NOACCEL
        8x16                 12x22
        MilleniumI   G200    MilleniumI   G200
8bpp    16.42         9.54   12.33         9.13
16bpp   21.00        15.70   19.11        15.02
24bpp   36.66        36.66   35.00        35.00
32bpp   35.00        30.00   33.85        28.66

ACCEL, nofastfont
        8x16                 12x22                6x11
	MilleniumI   G200    MilleniumI   G200    MilleniumI   G200
8bpp     7.79         7.24   13.55         7.78   30.00        21.01
16bpp    9.13         7.78   16.16         7.78   30.00        21.01
24bpp   14.17        10.72   18.69        10.24   34.99        21.01
32bpp   16.15	     16.16   18.73        13.09   34.99        21.01

ACCEL, fastfont
        8x16                 12x22                6x11
	MilleniumI   G200    MilleniumI   G200    MilleniumI   G200
8bpp     8.41         6.01    6.54         4.37   16.00        10.51
16bpp    9.54         9.12    8.76         6.17   17.52        14.01
24bpp   15.00        12.36   11.67        10.00   22.01        18.32
32bpp   16.18        18.29*  12.71        12.74   24.44        21.00

TEXT
        8x16
	MilleniumI   G200
TEXT     3.29         1.50

	
* Yes, it is slower than Millenium I.
--
Petr Vandrovec <vandrove@vc.cvut.cz>
