Annotation of wikisrc/users/rkujawa/g-rex.mdwn, revision 1.5

1.1       rkujawa     1: [[!meta title="G-REX"]]
                      2: 
                      3: Programming the G-REX PCI bridge
1.2       rkujawa     4: 
1.5     ! rkujawa     5: document version 0.2 - THIS IS A WORK IN PROGRESS!
1.1       rkujawa     6: 
                      7: # 0. Introduction
                      8: 
1.4       rkujawa     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...
1.1       rkujawa    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: 
1.3       rkujawa    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 
1.4       rkujawa    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: ;-). 
1.3       rkujawa    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.
1.1       rkujawa    31: 
1.5     ! rkujawa    32: All memory spaces of G-REX are directly visible and addressable in Amiga memory
        !            33: space, unlike in Mediator. Firmware allocates memory space as needed, depending
        !            34: on what cards are installed.
        !            35: 
1.1       rkujawa    36: # 2. Memory map
                     37: 
1.3       rkujawa    38: G-REX is configured as multipie AutoConf boards. Confusingly, they all have the same vendor (8512) and product (101).
1.1       rkujawa    39: 
                     40: 0xFFFA0000 - PCI I/O register space, 64KB.
1.2       rkujawa    41: 
1.1       rkujawa    42: 0xFFFC0000 - PCI configuration space, 128KB.
1.2       rkujawa    43: 
1.1       rkujawa    44: 0xFFFE0000 - Bridge configuration registers, 4kB.
                     45: 
                     46: 0x80000000 - PCI memory space, variable size and number of boards, depending on cards installed. 
                     47: 
1.4       rkujawa    48: # 2a. PCI configuration space (0xFFFA0000)
1.1       rkujawa    49: 
1.3       rkujawa    50: Access to configuration space is a bit tricky. Be warned that access to 
                     51: addresses not used by G-REX generates bus error (esp. to configuration 
                     52: locations which are unused because there is no card in the slot). Depending on 
                     53: how these errors are supported in your OS, it may be important to trap them and
                     54: handle correctly. 
1.1       rkujawa    55: 
1.4       rkujawa    56: Configuration data for first slot seems to be accessible at offset +0x1000 (on 
                     57: CVPPC/BVPPC there's aslo a mirror on +0x0).
1.1       rkujawa    58: 
                     59: [TO BE COMPLETED]
                     60: 
1.4       rkujawa    61: # 2b. PCI I/O registers space (0xFFFC0000)
1.1       rkujawa    62: 
                     63: This space offers access to I/O registers of all PCI cards.
                     64: 
1.5     ! rkujawa    65: On G-REX BAR addresses in this space are treated as absolute.
        !            66: 
        !            67: On CVPPC/BVPPC BAR addresses in this space are treated as relative to 
        !            68: 0xFFFA0000. Card with I/O BAR set to 0x100 will actually be available 
        !            69: at 0xFFFA0100. 
1.1       rkujawa    70: 
1.4       rkujawa    71: # 2c. PCI memory space (0x80000000)
1.1       rkujawa    72: 
1.3       rkujawa    73: This space offers access to memory (and memory-mapped registers) of PCI cards. 
                     74: Each PCI memory BAR is assigned a separate AutoConf board during firmware 
1.4       rkujawa    75: initialization.
                     76: 
                     77: For example Voodoo 3, which has two 32MB memory BARs, will be visible as 
                     78: two 8512/101 boards somewhere at 0x80000000 (or later).
1.1       rkujawa    79: 
1.3       rkujawa    80: Addresses in this space are treated as absolute. Memory BAR register set to 
1.5     ! rkujawa    81: 0x80000000 means it is configured at this address.
        !            82: 
        !            83: On CVPPC/BVPPC this space is present at different address - 0xE0000000.
1.1       rkujawa    84: 
                     85: # 2d. Bridge configuration registers
                     86: 
                     87: Offset - meaning
1.3       rkujawa    88: 
1.1       rkujawa    89: 0x0000 - Endianness swapper mode, write 0x02 to switch bridge into big endian mode
1.3       rkujawa    90: 
1.1       rkujawa    91: 0x0010 - Interrupt enable, write 0x01 to enable interrupts (INT2 on Amiga side)
                     92: 
                     93: No need to fiddle with these registers, as they've been already configured properly by the firmware.
                     94: 
1.5     ! rkujawa    95: # 3. Reconfiguring the bus
1.1       rkujawa    96: 
1.3       rkujawa    97: If needed, it's possible to reconfigure bus just by writing new values into 
                     98: configuration space. Keep in mind that any previously initialized chips will 
                     99: need to be reset and initialized again (for example 3Dfx Voodoo 3, which is
1.1       rkujawa   100: initialized by the firmware so it can display early startup menu). 
                    101: 
                    102: # 4. Interrupts
                    103: 
1.3       rkujawa   104: All interrupts are converted into Amiga INT2 interrupt. There's no such thing 
1.5     ! rkujawa   105: as interrupt acknowledge register. However, there seems to be an interrupt 
        !           106: enable register (see "Bridge configuration registers" above).
1.1       rkujawa   107: 
                    108: # 5. DMA
                    109: 
1.5     ! rkujawa   110: The bridge is certainly capable of real busmaster DMA, but it needs further 
        !           111: reverse engineering.
1.1       rkujawa   112: 
                    113: [TO BE COMPLETED]
                    114: 
1.3       rkujawa   115: There were at least two different revisions of G-REX 1200. Later revision 
1.5     ! rkujawa   116: probably does support DMA in first two slots. I'm not sure if it is possible
        !           117: to detect revision of the G-REX in software.
1.1       rkujawa   118: 
                    119: G-REX 4000D probably has busmaster DMA capability in all slots.
                    120: 
                    121: # 6. Sample PCI bridge driver implementation
                    122: 
1.3       rkujawa   123: The NetBSD [[p5pb|http://netbsd.gw.com/cgi-bin/man-cgi?p5pb+4.amiga+NetBSD-current]] 
                    124: driver serves as an example driver implementation. It was written using the 
                    125: same knowledge that went into this document.
                    126: 
                    127: The driver consists of several files in [[src/sys/arch/amiga/pci|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/]] directory.
                    128: 
                    129: p5membar.c - Dummy driver handling AutoConf resources.
                    130: p5membarvar.h - Structures used by the p5membar.
                    131: p5pb.c - Main driver code.
                    132: p5pbreg.h - Inlcude file containing register locations.
                    133: p5pbvar.h - Structures used by the p5pb.
                    134: 
                    135: 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   136: 
1.4       rkujawa   137: # 7. Thanks
                    138: 
                    139: [[AmiBay|http://www.amibay.com]] users d0pefish and ramborolf helped testing 
                    140: early versions of p5pb driver. Without their help this document would not 
                    141: exist.
                    142: 

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