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