1: [[!meta title="G-REX"]]
3: Programming the G-REX PCI bridge
5: document version 0.4
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: # 1a. Hardware
24: Three versions of G-REX exist:
26: * G-REX 1200 (for Amiga 1200 equipped with BlizzardPPC)
27: * G-REX 4000D (for Amiga 4000 equipped with CyberStormPPC)
28: * G-REX 4000T (for Amiga 4000T equipped with CyberStormPPC)
30: There were at least two different revisions of G-REX 1200. Later revision
31: (marked "Neue Version") probably does support DMA in first two slots. I'm not
32: sure if it is possible to detect revision of the G-REX in software.
34: Blizzard PPC hardware revision 0 is not compatible with G-REX
35: (revision 2 is certainly compatible, not sure about revision 1).
37: There's a rumor that most G-REX 4000T were recalled due to hardware problem.
39: G-REX is connected to local expansion slot present on CyberStorm PPC and
40: Blizzard PPC. These slots have different physical connectors but signals seem
41: to be mostly the same.
43: The bridge itself is an evolution of PCI bridge used previously on
44: CyberVisionPPC and BlizzardVisionPPC cards. These products share a lot of
45: similiarities (at least when it comes to PCI interface). In fact CVPPC/BVPPC
46: can be treated as a special one-slot version of G-REX. Maybe actually it's the
47: other way around ;-).
49: All memory spaces of G-REX are directly visible and addressable in Amiga memory
50: space, unlike in Mediator. Firmware allocates memory space as needed, depending
51: on what cards are installed.
53: # 1b. Firmware
55: G-REX firmware is a part of Flash ROM present on Blizzard PPC and CyberStorm
56: PPC boards. Known CSPPC firmware revisions supporting G-REX include 44.69 and
59: It does the dirty job of assigning PCI resources (BARs, interrupt lines,
60: etc.) before the OS is running. Therefore G-REX does not need any special
63: # 2. Memory map
65: G-REX is configured as multipie AutoConf boards. Confusingly, they all have the
66: same vendor (8512) and product (101).
68: 0xFFFA0000 - PCI I/O register space, 64KB.
70: 0xFFFC0000 - PCI configuration space, 128KB.
72: 0xFFFE0000 - Bridge configuration registers, 4kB.
74: 0x80000000 - PCI memory space, variable size and number of boards, depending on cards installed.
76: # 2a. PCI configuration space (0xFFFC0000)
78: Access to configuration space is a bit tricky. Be warned that access to
79: addresses not used by G-REX generates bus error (esp. to configuration
80: locations which are unused because there is no card in the slot). Depending on
81: how these errors are supported in your OS, it may be important to trap them and
82: handle correctly.
84: Configuration data for first slot (device 0) is accessible at offset +0x1000,
85: location for the next slots can be obtained by shifting the bit:
87: Configuration space address + (offset << device number)
89: For example to obtain configuration space for the second slot (device 1):
91: 0xFFFC0000 + (0x1000 << 1) = 0xFFFC2000
93: For the third slot (device 2):
95: 0xFFFC0000 + (0x1000 << 2) = 0xFFFC4000
97: and so on.
99: How to access device functions is not well analyzed, however funtion 0 is
100: always available at address computed by the above equation. Function 1 is
101: available at offset +0x100. One could assume that accessing the next
102: device functions is possible by shifting the bit (as with device access),
103: but that was not tested, becasue cards with more than two functions are not
106: On CVPPC/BVPPC configuration space is accessible at offset +0x0 (but there
107: are also mirrors through whole configuration space).
109: See [[p5pb_pci_conf_read()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_pci_conf_read]] and [[p5pb_pci_conf_write()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_pci_conf_read]] functions.
111: # 2b. PCI I/O registers space (0xFFFA0000)
113: This space offers access to I/O registers of all PCI cards.
115: On G-REX BAR addresses in this space are treated as absolute.
117: On CVPPC/BVPPC BAR addresses in this space are treated as relative to
118: 0xFFFA0000. Card with I/O BAR set to 0x100 will actually be available
119: at 0xFFFA0100.
121: # 2c. PCI memory space (0x80000000)
123: This space offers access to memory (and memory-mapped registers) of PCI cards.
124: Each PCI memory BAR is assigned a separate AutoConf board during firmware
127: For example Voodoo 3, which has two 32MB memory BARs, will be visible as
128: two 8512/101 boards somewhere at 0x80000000 (or later).
130: Addresses in this space are treated as absolute. Memory BAR register set to
131: 0x80000000 means it is configured at this address.
133: On CVPPC/BVPPC this space is present at different address - 0xE0000000.
135: # 2d. Bridge configuration registers (0xFFFE0000)
137: Offset - meaning
139: 0x0000 - Endianness swapper mode, write 0x02 to switch bridge into
140: big endian mode
142: 0x0010 - Interrupt enable, write 0x01 to enable interrupts (INT2 on Amiga side)
144: No need to fiddle with these registers, as they've been already configured
145: properly by the firmware.
147: # 3. Detecting the G-REX
149: Since AutoConf entries are created by the firmware, it is not possible to
150: detect G-REX easily if the correct firmware is not installed.
152: Detecting the G-REX is done by looking for Phase5 vendor ID (8512) and product
153: ID 101. Keep in mind that there will be more than one such board present, as
154: expained above.
156: It is possible to misdetect CVPPC/BVPPC as G-REX, since it uses the same vendor
157: and product ID if G-REX firmware is installed. With older firmware versions
158: these cards have no associated AutoConf entries.
160: Differentiating between CVPPC/BVPPC and G-REX in this situation is possible
161: by looking for Texas Instruments TVP4020 vendor and product ID at the beginning
162: of PCI configuration space. Configuration data for Permedia 2 chip will be
163: available at offset 0x0 on CVPPC/BVPPC, but on G-REX first slot is located
164: at offset 0x1000. See [[p5pb_identify_bridge()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_identify_bridge]]
165: and [[p5pb_cvppc_probe()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_cvppc_probe]] functions
166: in the NetBSD driver.
168: # 4. Reconfiguring the bus
170: If needed, it's possible to reconfigure bus just by writing new values into
171: configuration space. Keep in mind that any previously initialized chips will
172: need to be reset and initialized again (for example 3Dfx Voodoo 3, which is
173: initialized by the firmware so it can display early startup menu).
175: # 5. Interrupts
177: All interrupts are converted into Amiga INT2 interrupt. There's no such thing
178: as interrupt acknowledge register. However, there seems to be an interrupt
179: enable register (see "Bridge configuration registers" above).
181: # 6. DMA
183: The bridge is certainly capable of real busmaster DMA, but it needs further
184: reverse engineering.
186: [TO BE COMPLETED]
189: G-REX 4000D probably has busmaster DMA capability in all slots. G-REX 1200 has
190: busmaster DMA in first or two first slots depending on hardware revision.
192: # 7. Sample PCI bridge driver implementation
194: The NetBSD [[p5pb|http://netbsd.gw.com/cgi-bin/man-cgi?p5pb+4.amiga+NetBSD-current]]
195: driver serves as an example driver implementation. It was written using the
196: same knowledge that went into this document.
198: The driver consists of several files in [[src/sys/arch/amiga/pci|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/]] directory.
200: * p5membar.c - Dummy driver handling AutoConf resources.
201: * p5membarvar.h - Structures used by the p5membar.
202: * p5pb.c - Main driver code.
203: * p5pbreg.h - Inlcude file containing register locations.
204: * p5pbvar.h - Structures used by the p5pb.
206: 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).
208: # 8. Thanks
210: [[AmiBay|http://www.amibay.com]] users d0pefish, ramborolf and hese helped
211: testing early versions of p5pb driver. Without their help this document would
212: not exist.
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