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Further extend G-REX doc.

    1: [[!meta title="G-REX"]]
    2: 
    3: Programming the G-REX PCI bridge
    4: 
    5: document version 0.1 - THIS IS A WORK IN PROGRESS!
    6: 
    7: # 0. Introduction
    8: 
    9: This document describes software/hardware interface of the G-REX PCI bridge 
   10: for Amiga computers. What you're reading is a result of reverse engineering, 
   11: which was long and difficult process. 
   12: 
   13: Next time when you're going to buy a hardware product for your Amiga, don't 
   14: forget to ask the vendor to make the programming documentation publicly 
   15: available! Remeber that hardware without software is just a piece of junk...
   16: and you can't write software without hardware documentation.
   17: 
   18: In case you've noticed an error in this document please let me know. 
   19: 
   20: # 1. Theory of operation
   21: 
   22: G-REX is an evolution of PCI bridge used previously on CyberVisionPPC and 
   23: BlizzardVisionPPC cards. These products share a lot of similiarities (at 
   24: least when it comes to PCI interface). In fact CVPPC/BVPPC can be treated as
   25: a special one-slot version of G-REX. Maybe actually it's the other way around
   26: ;-). 
   27: 
   28: Firmware does the dirty job of assigning PCI resources (BARs, interrupt lines, 
   29: etc.) before the OS is running. Therefore G-REX does not need any special 
   30: initialization.
   31: 
   32: # 2. Memory map
   33: 
   34: G-REX is configured as multipie AutoConf boards. Confusingly, they all have the same vendor (8512) and product (101).
   35: 
   36: 0xFFFA0000 - PCI I/O register space, 64KB.
   37: 
   38: 0xFFFC0000 - PCI configuration space, 128KB.
   39: 
   40: 0xFFFE0000 - Bridge configuration registers, 4kB.
   41: 
   42: 0x80000000 - PCI memory space, variable size and number of boards, depending on cards installed. 
   43: 
   44: # 2a. PCI configuration space (0xFFFA0000)
   45: 
   46: Access to configuration space is a bit tricky. Be warned that access to 
   47: addresses not used by G-REX generates bus error (esp. to configuration 
   48: locations which are unused because there is no card in the slot). Depending on 
   49: how these errors are supported in your OS, it may be important to trap them and
   50: handle correctly. 
   51: 
   52: Configuration data for first slot seems to be accessible at offset +0x1000 (on 
   53: CVPPC/BVPPC there's aslo a mirror on +0x0).
   54: 
   55: [TO BE COMPLETED]
   56: 
   57: # 2b. PCI I/O registers space (0xFFFC0000)
   58: 
   59: This space offers access to I/O registers of all PCI cards.
   60: 
   61: BAR addresses in this space are treated as relative to 0xFFFA0000. Card with 
   62: I/O BAR set to 0x100 will actually be available at 0xFFFA0100. 
   63: 
   64: # 2c. PCI memory space (0x80000000)
   65: 
   66: This space offers access to memory (and memory-mapped registers) of PCI cards. 
   67: Each PCI memory BAR is assigned a separate AutoConf board during firmware 
   68: initialization.
   69: 
   70: For example Voodoo 3, which has two 32MB memory BARs, will be visible as 
   71: two 8512/101 boards somewhere at 0x80000000 (or later).
   72: 
   73: Addresses in this space are treated as absolute. Memory BAR register set to 
   74: 0x80000000 means it is configured at this address.  
   75: 
   76: # 2d. Bridge configuration registers
   77: 
   78: Offset - meaning
   79: 
   80: 0x0000 - Endianness swapper mode, write 0x02 to switch bridge into big endian mode
   81: 
   82: 0x0010 - Interrupt enable, write 0x01 to enable interrupts (INT2 on Amiga side)
   83: 
   84: No need to fiddle with these registers, as they've been already configured properly by the firmware.
   85: 
   86: # 3. Reconfiguring the bus.
   87: 
   88: If needed, it's possible to reconfigure bus just by writing new values into 
   89: configuration space. Keep in mind that any previously initialized chips will 
   90: need to be reset and initialized again (for example 3Dfx Voodoo 3, which is
   91: initialized by the firmware so it can display early startup menu). 
   92: 
   93: # 4. Interrupts
   94: 
   95: All interrupts are converted into Amiga INT2 interrupt. There's no such thing 
   96: as interrupt acknowledge register.
   97: 
   98: # 5. DMA
   99: 
  100: The bridge is certainly capable of DMA, but it needs further reverse 
  101: engineering.
  102: 
  103: [TO BE COMPLETED]
  104: 
  105: There were at least two different revisions of G-REX 1200. Later revision 
  106: probably does support DMA in two slots.
  107: 
  108: G-REX 4000D probably has busmaster DMA capability in all slots.
  109: 
  110: # 6. Sample PCI bridge driver implementation
  111: 
  112: The NetBSD [[p5pb|http://netbsd.gw.com/cgi-bin/man-cgi?p5pb+4.amiga+NetBSD-current]] 
  113: driver serves as an example driver implementation. It was written using the 
  114: same knowledge that went into this document.
  115: 
  116: The driver consists of several files in [[src/sys/arch/amiga/pci|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/]] directory.
  117: 
  118: p5membar.c - Dummy driver handling AutoConf resources.
  119: p5membarvar.h - Structures used by the p5membar.
  120: p5pb.c - Main driver code.
  121: p5pbreg.h - Inlcude file containing register locations.
  122: p5pbvar.h - Structures used by the p5pb.
  123: 
  124: The p5pb does attach on top of p5bus, however p5membar drivers attach on top of zbus (since 8512/101 entries are seen as Zorro boards).
  125: 
  126: # 7. Thanks
  127: 
  128: [[AmiBay|http://www.amibay.com]] users d0pefish and ramborolf helped testing 
  129: early versions of p5pb driver. Without their help this document would not 
  130: exist.
  131: