Commit | Line | Data |
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9fa68eae KP |
1 | I tried the following framebuffer drivers: |
2 | ||
3 | - TRIDENTFB is full of bugs. Acceleration is broken for Blade3D | |
4 | graphics cores like the cyberblade/i1. It claims to support a great | |
5 | number of devices, but documentation for most of these devices is | |
6 | unfortunately not available. There is _no_ reason to use tridentfb | |
7 | for cyberblade/i1 + CRT users. VESAFB is faster, and the one | |
8 | advantage, mode switching, is broken in tridentfb. | |
9 | ||
10 | - VESAFB is used by many distributions as a standard. Vesafb does | |
11 | not support mode switching. VESAFB is a bit faster than the working | |
12 | configurations of TRIDENTFB, but it is still too slow, even if you | |
13 | use ypan. | |
14 | ||
15 | - EPIAFB (you'll find it on sourceforge) supports the Cyberblade/i1 | |
16 | graphics core, but it still has serious bugs and developement seems | |
17 | to have stopped. This is the one driver with TV-out support. If you | |
18 | do need this feature, try epiafb. | |
19 | ||
20 | None of these drivers was a real option for me. | |
21 | ||
22 | I believe that is unreasonable to change code that announces to support 20 | |
23 | devices if I only have more or less sufficient documentation for exactly one | |
24 | of these. The risk of breaking device foo while fixing device bar is too high. | |
25 | ||
26 | So I decided to start CyBlaFB as a stripped down tridentfb. | |
27 | ||
28 | All code specific to other Trident chips has been removed. After that there | |
29 | were a lot of cosmetic changes to increase the readability of the code. All | |
30 | register names were changed to those mnemonics used in the datasheet. Function | |
31 | and macro names were changed if they hindered easy understanding of the code. | |
32 | ||
33 | After that I debugged the code and implemented some new features. I'll try to | |
34 | give a little summary of the main changes: | |
35 | ||
36 | - calculation of vertical and horizontal timings was fixed | |
37 | ||
38 | - video signal quality has been improved dramatically | |
39 | ||
40 | - acceleration: | |
41 | ||
42 | - fillrect and copyarea were fixed and reenabled | |
43 | ||
44 | - color expanding imageblit was newly implemented, color | |
45 | imageblit (only used to draw the penguine) still uses the | |
46 | generic code. | |
47 | ||
48 | - init of the acceleration engine was improved and moved to a | |
49 | place where it really works ... | |
50 | ||
51 | - sync function has a timeout now and tries to reset and | |
52 | reinit the accel engine if necessary | |
53 | ||
54 | - fewer slow copyarea calls when doing ypan scrolling by using | |
55 | undocumented bit d21 of screen start address stored in | |
56 | CR2B[5]. BIOS does use it also, so this should be safe. | |
57 | ||
58 | - cyblafb rejects any attempt to set modes that would cause vclk | |
59 | values above reasonable 230 MHz. 32bit modes use a clock | |
60 | multiplicator of 2, so fbset does show the correct values for | |
61 | pixclock but not for vclk in this case. The fbset limit is 115 MHz | |
62 | for 32 bpp modes. | |
63 | ||
64 | - cyblafb rejects modes known to be broken or unimplemented (all | |
65 | interlaced modes, all doublescan modes for now) | |
66 | ||
67 | - cyblafb now works independant of the video mode in effect at startup | |
68 | time (tridentfb does not init all needed registers to reasonable | |
69 | values) | |
70 | ||
71 | - switching between video modes does work reliably now | |
72 | ||
73 | - the first video mode now is the one selected on startup using the | |
74 | vga=???? mechanism or any of | |
75 | - 640x480, 800x600, 1024x768, 1280x1024 | |
76 | - 8, 16, 24 or 32 bpp | |
77 | - refresh between 50 Hz and 85 Hz, 1 Hz steps (1280x1024-32 | |
78 | is limited to 63Hz) | |
79 | ||
80 | - pci retry and pci burst mode are settable (try to disable if you | |
81 | experience latency problems) | |
82 | ||
83 | - built as a module cyblafb might be unloaded and reloaded using | |
84 | the vfb module and con2vt or might be used together with vesafb | |
85 |