[PATCH] framebuffer: new driver for cyberblade/i1 graphics core

This is a framebuffer driver for the Cyberblade/i1 graphics core.

Currently tridenfb claims to support the cyberblade/i1 graphics core.  This
is of very limited truth.  Even vesafb is faster and provides more working
modes and a much better quality of the video signal.  There is a great
number of bugs in tridentfb ...  but most often it is impossible to decide
if these bugs are real bugs or if fixing them for the cyberblade/i1 core
would break support for one of the other supported chips.

Tridentfb seems to be unmaintained,and documentation for most of the
supported chips is not available.  So "fixing" cyberblade/i1 support inside
of tridentfb was not an option, it would have caused numerous
if(CYBERBLADEi1) else ...  cases and would have rendered the code to be
almost unmaintainable.

A first version of this driver was published on 2005-07-31.  A fix for a
bug reported by Jochen Hein was integrated as well as some changes
requested by Antonino A.  Daplas.

A message has been added to tridentfb to inform current users of tridentfb
to switch to cyblafb if the cyberblade/i1 graphics core is detected.

This patch is one logical change, but because of the included documentation
it is bigger than 70kb.  Therefore it is not sent to lkml and
linux-fbdev-devel,

Signed-off-by: Knut Petersen <Knut_Petersen@t-online.de>
Cc: Muli Ben-Yehuda <mulix@mulix.org>
Acked-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 206 insertions, 0 deletions

diff --git a/Documentation/fb/cyblafb/usage b/Documentation/fb/cyblafb/usage
new file mode 100644
index 000000000000..e627c8f54211
--- /dev/null
+++ b/Documentation/fb/cyblafb/usage
@@ -0,0 +1,206 @@
+CyBlaFB is a framebuffer driver for the Cyberblade/i1 graphics core integrated
+into the VIA Apollo PLE133 (aka vt8601) south bridge. It is developed and
+tested using a VIA EPIA 5000 board.
+
+Cyblafb - compiled into the kernel or as a module?
+==================================================
+
+You might compile cyblafb either as a module or compile it permanently into the
+kernel.
+
+Unless you have a real reason to do so you should not compile both vesafb and
+cyblafb permanently into the kernel. It's possible and it helps during the
+developement cycle, but it's useless and will at least block some otherwise
+usefull memory for ordinary users.
+
+Selecting Modes
+===============
+
+        Startup Mode
+        ============
+
+        First of all, you might use the "vga=???" boot parameter as it is
+        documented in vesafb.txt and svga.txt. Cyblafb will detect the video
+        mode selected and will use the geometry and timings found by
+        inspecting the hardware registers.
+
+                video=cyblafb vga=0x317
+
+        Alternatively you might use a combination of the mode, ref and bpp
+        parameters. If you compiled the driver into the kernel, add something
+        like this to the kernel command line:
+
+                video=cyblafb:1280x1024,bpp=16,ref=50 ...
+
+        If you compiled the driver as a module, the same mode would be
+        selected by the following command:
+
+                modprobe cyblafb mode=1280x1024 bpp=16 ref=50 ...
+
+        None of the modes possible to select as startup modes are affected by
+        the problems described at the end of the next subsection.
+
+        Mode changes using fbset
+        ========================
+
+        You might use fbset to change the video mode, see "man fbset". Cyblafb
+        generally does assume that you know what you are doing. But it does
+        some checks, especially those that are needed to prevent you from
+        damaging your hardware.
+
+                - only 8, 16, 24 and 32 bpp video modes are accepted
+                - interlaced video modes are not accepted
+                - double scan video modes are not accepted
+                - if a flat panel is found, cyblafb does not allow you
+                  to program a resolution higher than the physical
+                  resolution of the flat panel monitor
+                - cyblafb does not allow xres to differ from xres_virtual
+                - cyblafb does not allow vclk to exceed 230 MHz. As 32 bpp
+                  and (currently) 24 bit modes use a doubled vclk internally,
+                  the dotclock limit as seen by fbset is 115 MHz for those
+                  modes and 230 MHz for 8 and 16 bpp modes.
+
+        Any request that violates the rules given above will be ignored and
+        fbset will return an error.
+
+        If you program a virtual y resolution higher than the hardware limit,
+        cyblafb will silently decrease that value to the highest possible
+        value.
+
+        Attempts to disable acceleration are ignored.
+
+        Some video modes that should work do not work as expected. If you use
+        the standard fb.modes, fbset 640x480-60 will program that mode, but
+        you will see a vertical area, about two characters wide, with only
+        much darker characters than the other characters on the screen.
+        Cyblafb does allow that mode to be set, as it does not violate the
+        official specifications. It would need a lot of code to reliably sort
+        out all invalid modes, playing around with the margin values will
+        give a valid mode quickly. And if cyblafb would detect such an invalid
+        mode, should it silently alter the requested values or should it
+        report an error? Both options have some pros and cons. As stated
+        above, none of the startup modes are affected, and if you set
+        verbosity to 1 or higher, cyblafb will print the fbset command that
+        would be needed to program that mode using fbset.
+
+
+Other Parameters
+================
+
+
+crt             don't autodetect, assume monitor connected to
+                standard VGA connector
+
+fp              don't autodetect, assume flat panel display
+                connected to flat panel monitor interface
+
+nativex         inform driver about native x resolution of
+                flat panel monitor connected to special
+                interface (should be autodetected)
+
+stretch         stretch image to adapt low resolution modes to
+                higer resolutions of flat panel monitors
+                connected to special interface
+
+center          center image to adapt low resolution modes to
+                higer resolutions of flat panel monitors
+                connected to special interface
+
+memsize         use if autodetected memsize is wrong ...
+                should never be necessary
+
+nopcirr         disable PCI read retry
+nopciwr         disable PCI write retry
+nopcirb         disable PCI read bursts
+nopciwb         disable PCI write bursts
+
+bpp             bpp for specified modes
+                valid values: 8 || 16 || 24 || 32
+
+ref             refresh rate for specified mode
+                valid values: 50 <= ref <= 85
+
+mode            640x480 or 800x600 or 1024x768 or 1280x1024
+                if not specified, the startup mode will be detected
+                and used, so you might also use the vga=??? parameter
+                described in vesafb.txt. If you do not specify a mode,
+                bpp and ref parameters are ignored.
+
+verbosity       0 is the default, increase to at least 2 for every
+                bug report!
+
+vesafb          allows cyblafb to be loaded after vesafb has been
+                loaded. See sections "Module unloading ...".
+
+
+Development hints
+=================
+
+It's much faster do compile a module and to load the new version after
+unloading the old module than to compile a new kernel and to reboot. So if you
+try to work on cyblafb, it might be a good idea to use cyblafb as a module.
+In real life, fast often means dangerous, and that's also the case here. If
+you introduce a serious bug when cyblafb is compiled into the kernel, the
+kernel will lock or oops with a high probability before the file system is
+mounted, and the danger for your data is low. If you load a broken own version
+of cyblafb on a running system, the danger for the integrity of the file
+system is much higher as you might need a hard reset afterwards. Decide
+yourself.
+
+Module unloading, the vfb method
+================================
+
+If you want to unload/reload cyblafb using the virtual framebuffer, you need
+to enable vfb support in the kernel first. After that, load the modules as
+shown below:
+
+        modprobe vfb vfb_enable=1
+        modprobe fbcon
+        modprobe cyblafb
+        fbset -fb /dev/fb1 1280x1024-60 -vyres 2662
+        con2fb /dev/fb1 /dev/tty1
+        ...
+
+If you now made some changes to cyblafb and want to reload it, you might do it
+as show below:
+
+        con2fb /dev/fb0 /dev/tty1
+        ...
+        rmmod cyblafb
+        modprobe cyblafb
+        con2fb /dev/fb1 /dev/tty1
+        ...
+
+Of course, you might choose another mode, and most certainly you also want to
+map some other /dev/tty* to the real framebuffer device. You might also choose
+to compile fbcon as a kernel module or place it permanently in the kernel.
+
+I do not know of any way to unload fbcon, and fbcon will prevent the
+framebuffer device loaded first from unloading. [If there is a way, then
+please add a description here!]
+
+Module unloading, the vesafb method
+===================================
+
+Configure the kernel:
+
+        <*> Support for frame buffer devices
+        [*]   VESA VGA graphics support
+        <M>   Cyberblade/i1 support
+
+Add e.g. "video=vesafb:ypan vga=0x307" to the kernel parameters. The ypan
+parameter is important, choose any vga parameter you like as long as it is
+a graphics mode.
+
+After booting, load cyblafb without any mode and bpp parameter and assign
+cyblafb to individual ttys using con2fb, e.g.:
+
+        modprobe cyblafb vesafb=1
+        con2fb /dev/fb1 /dev/tty1
+
+Unloading cyblafb works without problems after you assign vesafb to all
+ttys again, e.g.:
+
+        con2fb /dev/fb0 /dev/tty1
+        rmmod cyblafb
+