Annotation of wikisrc/users/rkujawa/g-rex.mdwn, revision 1.1
1.1 ! rkujawa 1: [[!meta title="G-REX"]]
! 3: Programming the G-REX PCI bridge
! 4: version 0 - THIS IS A WORK IN PROGRESS!
! 6: # 0. Introduction
! 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.
! 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.
! 15: In case you've noticed an error in this document please let me know.
! 17: # 1. Theory of operation
! 19: G-REX is an evolution of PCI bridge used previously on CyberVisionPPC and BlizzardVisionPPC cards. These
! 20: products share a lot of similiarities.
! 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.
! 25: # 2. Memory map
! 27: G-REX is configured as multipie AutoConf boards. Confusingly, they all have the same vendor and product ID.
! 29: 0xFFFA0000 - PCI I/O register space, 64KB.
! 30: 0xFFFC0000 - PCI configuration space, 128KB.
! 31: 0xFFFE0000 - Bridge configuration registers, 4kB.
! 33: 0x80000000 - PCI memory space, variable size and number of boards, depending on cards installed.
! 35: # 2a. PCI configuration space
! 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.
! 41: Configuration data for first slot seems to be accessible at +0x1000.
! 43: [TO BE COMPLETED]
! 45: # 2b. PCI I/O registers space
! 47: This space offers access to I/O registers of all PCI cards.
! 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.
! 52: # 2c. PCI memory space
! 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.
! 57: Addresses in this space are treated as absolute. Memory BAR register set to 0x80000000 means it is configured at this
! 58: address.
! 60: # 2d. Bridge configuration registers
! 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)
! 66: No need to fiddle with these registers, as they've been already configured properly by the firmware.
! 68: # 3. Reconfiguring the bus.
! 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).
! 74: # 4. Interrupts
! 76: All interrupts are converted into Amiga INT2 interrupt. There's no such thing as interrupt acknowledge register.
! 78: # 5. DMA
! 80: The bridge is certainly capable of DMA, but it needs further reverse engineering.
! 82: [TO BE COMPLETED]
! 84: There were at least two different revisions of G-REX 1200. Later revision probably does support DMA in all slots.
! 86: G-REX 4000D probably has busmaster DMA capability in all slots.
! 88: # 6. Sample PCI bridge driver implementation
! 90: The NetBSD p5pb driver serves as example driver implementation. It was written using the same knowledge that went
! 91: into this document.
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