1: [[!meta title="G-REX"]]
3: Programming the G-REX PCI bridge
5: document version 0.2 - THIS IS A WORK IN PROGRESS!
7: # 0. Introduction
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.
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.
18: In case you've noticed an error in this document please let me know.
20: # 1. Theory of operation
22: G-REX is connected to local expansion slot present on CyberStorm PPC and
23: Blizzard PPC.
25: G-REX is an evolution of PCI bridge used previously on CyberVisionPPC and
26: BlizzardVisionPPC cards. These products share a lot of similiarities (at
27: least when it comes to PCI interface). In fact CVPPC/BVPPC can be treated as
28: a special one-slot version of G-REX. Maybe actually it's the other way around
31: Firmware does the dirty job of assigning PCI resources (BARs, interrupt lines,
32: etc.) before the OS is running. Therefore G-REX does not need any special
35: All memory spaces of G-REX are directly visible and addressable in Amiga memory
36: space, unlike in Mediator. Firmware allocates memory space as needed, depending
37: on what cards are installed.
39: Blizzard PPC hardware revision 0 is not compatible with G-REX
40: (which revisions are compatible?).
42: # 2. Memory map
44: G-REX is configured as multipie AutoConf boards. Confusingly, they all have the
45: same vendor (8512) and product (101).
47: 0xFFFA0000 - PCI I/O register space, 64KB.
49: 0xFFFC0000 - PCI configuration space, 128KB.
51: 0xFFFE0000 - Bridge configuration registers, 4kB.
53: 0x80000000 - PCI memory space, variable size and number of boards, depending on cards installed.
55: # 2a. PCI configuration space (0xFFFA0000)
57: Access to configuration space is a bit tricky. Be warned that access to
58: addresses not used by G-REX generates bus error (esp. to configuration
59: locations which are unused because there is no card in the slot). Depending on
60: how these errors are supported in your OS, it may be important to trap them and
61: handle correctly.
63: Configuration data for first slot seems to be accessible at offset +0x1000 (on
64: CVPPC/BVPPC there's aslo a mirror on +0x0).
66: [TO BE COMPLETED]
68: # 2b. PCI I/O registers space (0xFFFC0000)
70: This space offers access to I/O registers of all PCI cards.
72: On G-REX BAR addresses in this space are treated as absolute.
74: On CVPPC/BVPPC BAR addresses in this space are treated as relative to
75: 0xFFFA0000. Card with I/O BAR set to 0x100 will actually be available
76: at 0xFFFA0100.
78: # 2c. PCI memory space (0x80000000)
80: This space offers access to memory (and memory-mapped registers) of PCI cards.
81: Each PCI memory BAR is assigned a separate AutoConf board during firmware
84: For example Voodoo 3, which has two 32MB memory BARs, will be visible as
85: two 8512/101 boards somewhere at 0x80000000 (or later).
87: Addresses in this space are treated as absolute. Memory BAR register set to
88: 0x80000000 means it is configured at this address.
90: On CVPPC/BVPPC this space is present at different address - 0xE0000000.
92: # 2d. Bridge configuration registers
94: Offset - meaning
96: 0x0000 - Endianness swapper mode, write 0x02 to switch bridge into big endian mode
98: 0x0010 - Interrupt enable, write 0x01 to enable interrupts (INT2 on Amiga side)
100: No need to fiddle with these registers, as they've been already configured
101: properly by the firmware.
103: # 3. Detecting the G-REX
105: Since AutoConf entries are created by the firmware, G-REX needs a special
106: firmware for CyberStorm PPC and Blizzard PPC. Known CSPPC firmware revisions
107: supporting G-REX include 44.69 and 44.71.
109: Detecting the G-REX is done by looking for Phase5 vendor ID (8512) and product
110: ID 101. Keep in mind that there will be more than one such board present, as
111: expained above.
113: It is possible to misdetect CVPPC/BVPPC as G-REX, since it uses the same vendor
114: and product ID if G-REX firmware is installed. With older firmware versions
115: these cards have no associated AutoConf entries.
117: Differentiating between CVPPC/BVPPC and G-REX in this situation is possible
118: by looking for Texas Instruments TVP4020 vendor and product ID at the beginning
119: of PCI configuration space. Configuration data for Permedia 2 chip will be
120: available at offset 0x0 on CVPPC/BVPPC, but on G-REX first slot is located
121: at offset 0x1000. See [[p5pb_identify_bridge()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_identify_bridge]] and [[p5pb_cvppc_probe()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_cvppc_probe]] functions
122: in the NetBSD driver.
124: # 4. Reconfiguring the bus
126: If needed, it's possible to reconfigure bus just by writing new values into
127: configuration space. Keep in mind that any previously initialized chips will
128: need to be reset and initialized again (for example 3Dfx Voodoo 3, which is
129: initialized by the firmware so it can display early startup menu).
131: # 5. Interrupts
133: All interrupts are converted into Amiga INT2 interrupt. There's no such thing
134: as interrupt acknowledge register. However, there seems to be an interrupt
135: enable register (see "Bridge configuration registers" above).
137: # 6. DMA
139: The bridge is certainly capable of real busmaster DMA, but it needs further
140: reverse engineering.
142: [TO BE COMPLETED]
144: There were at least two different revisions of G-REX 1200. Later revision
145: probably does support DMA in first two slots. I'm not sure if it is possible
146: to detect revision of the G-REX in software.
148: G-REX 4000D probably has busmaster DMA capability in all slots.
150: # 7. Sample PCI bridge driver implementation
152: The NetBSD [[p5pb|http://netbsd.gw.com/cgi-bin/man-cgi?p5pb+4.amiga+NetBSD-current]]
153: driver serves as an example driver implementation. It was written using the
154: same knowledge that went into this document.
156: The driver consists of several files in [[src/sys/arch/amiga/pci|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/]] directory.
158: * p5membar.c - Dummy driver handling AutoConf resources.
159: * p5membarvar.h - Structures used by the p5membar.
160: * p5pb.c - Main driver code.
161: * p5pbreg.h - Inlcude file containing register locations.
162: * p5pbvar.h - Structures used by the p5pb.
164: 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).
166: # 8. Thanks
168: [[AmiBay|http://www.amibay.com]] users d0pefish and ramborolf helped testing
169: early versions of p5pb driver. Without their help this document would not
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