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diff --git a/xorg-server/hw/xfree86/doc/devel/Domain.note b/xorg-server/hw/xfree86/doc/devel/Domain.note new file mode 100644 index 000000000..ce0812b22 --- /dev/null +++ b/xorg-server/hw/xfree86/doc/devel/Domain.note @@ -0,0 +1,159 @@ +The purpose of the changes described here is to implement a more general +framework for multi-head on systems with more than one host-to-PCI bridge. +The changes also implement a basic port of XFree86 to SPARC Solaris. + +These changes are derived from David S. Miller's submission #4653 to the +patch list. David Andrew of Sun Microsystems was also kind enough to +arrange for a hardware loan for development of these changes. + +These changes are known to work on several SPARC SunOS and UltraSPARC +Linux configurations. Linux kernel work is in progress to port these +changes to Linux/PowerPC. + +Several loose ends still need to be addressed before these changes can be +considered stable. The bulk of this note is devoted to enumerating what +remains to be done, along with other notes, broken down into various broad +categories. + +SPARC SunOS (aka Solaris) +------------------------- +- An overview of this XFree86 port is available in README.Solaris. +- The keyboard map code in hw/xfree86/os-support/sunos/sun_kbdEv.c needs + to be extended to handle more than only the sun5 keyboard I targeted it + for. Even for the sun5, the map is incomplete as several keys are not + mapped. What is there is just barely usable. +- On exit, the server will zero out /dev/fb, but that might not be the + right thing to do for all primary adapters. This does however + appear to emulate the behaviour of Sun's commercial servers. It also + eliminates the need for output drivers to save and restore video memory + contents. (They still need to save/restore the mode timing however.) + This also chimes into a long-standing XFree86 policy to not save/restore + video memory contents if the mode on entry is found to be non-VGA, a + policy several existing drivers comply with. +- The SBUS drivers (sunbw2, suncg14, suncg3, suncg6, sunffb, sunleo and + suntcx), the common layer's SBUS code and the fbdev driver have all + only been compile tested. There are likely to be Linux'isms within + them that remain to be dealt with. +- It still needs to be verified whether or not this work adversely + affected support for ix86 Solaris. + +UltraSPARC Linux +---------------- +- Although this code can be compiled using any Linux/SPARC64 kernel, it + can only run successfully using 2.4.12 or later. +- I haven't had time to sufficiently dig into XKB to properly configure it + for sun5 keyboards. Given XFree86 on Linux/SPARC has been around for a + while, it's likely someone has already done this, and I'd appreciate + receiving a copy of a working XF86Config input section. + +PowerPC Linux +------------- +- As mentioned above, kernel work is in progress to port this PCI scheme + to Linux/PowerPC. +- Aside from kernel work, the inX() and outX() definitions in compiler.h + will need to be changed to do something akin to their SPARC definitions, + i.e. consider their port argument to be a virtual address. + +Other Linux ports to multi-domain architectures +----------------------------------------------- +- Comments in os-support/bus/linuxPci.c document the kernel interface + required to port these changes. In short, Linux ports, such as Alpha + and mips, should follow SPARC and PowerPC's lead in providing support to + mmap() PCI devices through their /proc/bus/pci pseudo-files and to treat + such requests for host bridges as requests to mmap() space provided by + these bridges. + +Other OS's +---------- +- In the right hands, either linuxPci.c or sparcPci.c can be used as a + guide for what would need to be done to port this scheme to other OS's. + Perhaps the largest difference between the two (in terms of interface to + the common layer) is that the SunOS port includes internally generated + domain numbers in PCITAG's, whereas the Linux port doesn't need to. The + remainder of the PCI code (which is OS-independent) can handle either + scheme. +- Required entry points are xf86GetPciDomain(), xf86MapDomainMemory(), + xf86MapDomainIO() and xf86ReadDomainMemory(). Replacements for + xf86BusAccWindowsFromOS(), xf86PciBusAccWindowsFromOS() and + xf86AccResFromOS() might also be required. +- Development of these changes has detected the fact that the XFree86 port + to the PowerMax OS is broken, and has been for some time, i.e. since + shortly after its introduction, back in the 3.9* days. + +SPARC PCI (OS-independent) +-------------------------- +- The "Simba" PCI-to-PCI bridge used in SPARC's does not implement VGA + routing, as defined in the PCI specs. Fortunately, OpenPROM seems to + always route VGA resources to the bus with PCI connectors, but this also + causes the common layer to not mark any PCI adapter as primary. + +Multiple PCI domains (architecture- and OS-independent) +------------------------------------------------------- +- This implementation assumes every host-to-PCI bridge provides access to + a separate PCI domain. Each such domain provides three different + "address" spaces: PCI configuration, I/O and memory. The + implementation can also deal with situations where more than one PCI + domain share (different subsets of) the same PCI configuration space. I + have unconfirmed information that suggests it might be necessary to also + allow the sharing of PCI memory spaces. +- This implementation also assumes the CPU's physical address space + includes the entirety of each domain's I/O and memory spaces. I know + this'll need to be changed to deal with the so-called UniNorth bridge, + found on PowerPC's, which allows access to only a subset of the memory + space behind it. +- Ideally, the common layer should mark as primary up to one PCI adapter + per domain. This has yet to be done. +- Something needs to be done about PCI master aborts on primary buses. + For details on this, see my long-winded diatribe in sparcPci.c, and + related comments in linuxPci.c. Suffice it to say here that I see the + eventual implementation of host bridge drivers within XFree86 as + unavoidable at this point. +- DGA is broken on multi-domain platforms. The information passed to the + client to locate the framebuffer still needs to be revised. The best way + to deal with this is to change all drivers' OpenFramebuffer() function to + call a common layer routine to set the device name and displacements to be + returned to the DGA client. + +Output drivers +-------------- +Most drivers currently used on ix86 need(ed) source code changes. +- Calls to xf86ReadBIOS() and xf86MapVidMem() were replaced with calls to + xf86ReadDomainMemory() and xf86MapDomainMemory() respectively. Except + for the "ati" and "atimisc" modules, this has already been done. +- All ix86-style I/O port numbers need to be declared as an IOADDRESS, a + type defined in xf86Pci.h as "unsigned long". Such port numbers also + need to be offset by a displacement which is also defined as an + IOADDRESS. Before a driver's PreInit() is called, the common layer + makes this displacement available in ScrnInfoRec.domainIOBase. For + single-domain architectures, such as ix86, domainIOBase will always be + zero. Current use of vgaHWRec.PIOOffset has also been adjusted + accordingly. Some drivers have been changed to keep a copy of this + displacement in their private structure. Internally, an IOADDRESS is + actually a pointer that has been recasted to an unsigned long, but the + common layer "hides" this fact from the driver ABI, which means that I/O + port numbers, as seen by drivers, remain as integers rather than + addresses. Aside from the ati and atimisc modules, s3, sis and tseng + are the only modules left whose I/O still needs to be converted (I've + temporarily run out of steam). +- Note that these conversions are not necessarily sufficient to produce + drivers that will work on any given multi-domain architecture. A driver + that, for example, had endianness problems, still does. But, at least, + these conversions, along with the supporting common layer changes, make + PCI drivers more widely amenable to porting. +- rdinx(), wrinx(), modinx(), testrg(), testinx() and testinx2() are not + given enough information to allow for the relocation of their I/O. They + are consequently being deleted. The apm and ark drivers, the only + remaining callers of the first three, have been changed to use local + definitions instead. The last three (test*()) were already unused. +- As a temporary measure, these changes completely disable ISA-style + probing on SPARC's and PowerPC's. This means that driver calls to + xf86MatchIsaInstances(), while still valid, will always return detection + failure on SPARC's and PowerPC's. This will be dealt with when a more + general master abort handling scheme is implemented. +- I need to make a decision about the master abort issues mentionned above + before I can convert the "ati" and "atimisc" modules. Consequently, + these modules still need to be compiled with -DAVOID_CPIO on + multi-domain architectures, and support for Mach64 variants as + non-primary heads is not yet available. + +$XFree86$ |