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