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