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version 1.6, 2012/07/06 20:00:55	version 1.9, 2012/07/08 13:37:51
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Programming the G-REX PCI bridge	Programming the G-REX PCI bridge

document version 0.2 - THIS IS A WORK IN PROGRESS!	document version 0.3 - THIS IS A WORK IN PROGRESS!

# 0. Introduction	# 0. Introduction

Line 19 In case you've noticed an error in this	Line 19 In case you've noticed an error in this

# 1. Theory of operation	# 1. Theory of operation

G-REX is an evolution of PCI bridge used previously on CyberVisionPPC and	# 1a. Hardware
BlizzardVisionPPC cards. These products share a lot of similiarities (at
least when it comes to PCI interface). In fact CVPPC/BVPPC can be treated as
a special one-slot version of G-REX. Maybe actually it's the other way around
;-).

Firmware does the dirty job of assigning PCI resources (BARs, interrupt lines,	Three versions of G-REX exist:
etc.) before the OS is running. Therefore G-REX does not need any special
initialization.	* G-REX 1200 (for Amiga 1200 equipped with BlizzardPPC)
	* G-REX 4000D (for Amiga 4000 equipped with CyberStormPPC)
	* G-REX 4000T (for Amiga 4000T equipped with CyberStormPPC)

	There were at least two different revisions of G-REX 1200. Later revision
	(marked "Neue Version") probably does support DMA in first two slots. I'm not
	sure if it is possible to detect revision of the G-REX in software.

	Blizzard PPC hardware revision 0 is not compatible with G-REX
	(revision 2 is certainly compatible, not sure about revision 1).

	There's a rumor that most G-REX 4000T were recalled due to hardware problem.

	G-REX is connected to local expansion slot present on CyberStorm PPC and
	Blizzard PPC. These slots have different physical connectors but signals seem
	to be mostly the same.

	The bridge itself is an evolution of PCI bridge used previously on
	CyberVisionPPC and BlizzardVisionPPC cards. These products share a lot of
	similiarities (at least when it comes to PCI interface). In fact CVPPC/BVPPC
	can be treated as a special one-slot version of G-REX. Maybe actually it's the
	other way around ;-).

All memory spaces of G-REX are directly visible and addressable in Amiga memory	All memory spaces of G-REX are directly visible and addressable in Amiga memory
space, unlike in Mediator. Firmware allocates memory space as needed, depending	space, unlike in Mediator. Firmware allocates memory space as needed, depending
on what cards are installed.	on what cards are installed.

	# 1b. Firmware

	G-REX firmware is a part of Flash ROM present on Blizzard PPC and CyberStorm
	PPC boards. Known CSPPC firmware revisions supporting G-REX include 44.69 and
	44.71.

	It does the dirty job of assigning PCI resources (BARs, interrupt lines,
	etc.) before the OS is running. Therefore G-REX does not need any special
	initialization.

# 2. Memory map	# 2. Memory map

G-REX is configured as multipie AutoConf boards. Confusingly, they all have the same vendor (8512) and product (101).	G-REX is configured as multipie AutoConf boards. Confusingly, they all have the
	same vendor (8512) and product (101).

0xFFFA0000 - PCI I/O register space, 64KB.	0xFFFA0000 - PCI I/O register space, 64KB.

Line 82 Addresses in this space are treated as a	Line 110 Addresses in this space are treated as a

On CVPPC/BVPPC this space is present at different address - 0xE0000000.	On CVPPC/BVPPC this space is present at different address - 0xE0000000.

# 2d. Bridge configuration registers	# 2d. Bridge configuration registers (0xFFFE0000)

Offset - meaning	Offset - meaning

Line 93 Offset - meaning	Line 121 Offset - meaning
No need to fiddle with these registers, as they've been already configured	No need to fiddle with these registers, as they've been already configured
properly by the firmware.	properly by the firmware.

# 3. Reconfiguring the bus	# 3. Detecting the G-REX

	Since AutoConf entries are created by the firmware, it is not possible to
	detect G-REX easily if the correct firmware is not installed.

	Detecting the G-REX is done by looking for Phase5 vendor ID (8512) and product
	ID 101. Keep in mind that there will be more than one such board present, as
	expained above.

	It is possible to misdetect CVPPC/BVPPC as G-REX, since it uses the same vendor
	and product ID if G-REX firmware is installed. With older firmware versions
	these cards have no associated AutoConf entries.

	Differentiating between CVPPC/BVPPC and G-REX in this situation is possible
	by looking for Texas Instruments TVP4020 vendor and product ID at the beginning
	of PCI configuration space. Configuration data for Permedia 2 chip will be
	available at offset 0x0 on CVPPC/BVPPC, but on G-REX first slot is located
	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
	in the NetBSD driver.

	# 4. Reconfiguring the bus

If needed, it's possible to reconfigure bus just by writing new values into	If needed, it's possible to reconfigure bus just by writing new values into
configuration space. Keep in mind that any previously initialized chips will	configuration space. Keep in mind that any previously initialized chips will
need to be reset and initialized again (for example 3Dfx Voodoo 3, which is	need to be reset and initialized again (for example 3Dfx Voodoo 3, which is
initialized by the firmware so it can display early startup menu).	initialized by the firmware so it can display early startup menu).

# 4. Interrupts	# 5. Interrupts

All interrupts are converted into Amiga INT2 interrupt. There's no such thing	All interrupts are converted into Amiga INT2 interrupt. There's no such thing
as interrupt acknowledge register. However, there seems to be an interrupt	as interrupt acknowledge register. However, there seems to be an interrupt
enable register (see "Bridge configuration registers" above).	enable register (see "Bridge configuration registers" above).

# 5. DMA	# 6. DMA

The bridge is certainly capable of real busmaster DMA, but it needs further	The bridge is certainly capable of real busmaster DMA, but it needs further
reverse engineering.	reverse engineering.

[TO BE COMPLETED]	[TO BE COMPLETED]

There were at least two different revisions of G-REX 1200. Later revision
probably does support DMA in first two slots. I'm not sure if it is possible
to detect revision of the G-REX in software.

G-REX 4000D probably has busmaster DMA capability in all slots.	G-REX 4000D probably has busmaster DMA capability in all slots.

# 6. Sample PCI bridge driver implementation	# 7. Sample PCI bridge driver implementation

The NetBSD [[p5pb\|http://netbsd.gw.com/cgi-bin/man-cgi?p5pb+4.amiga+NetBSD-current]]	The NetBSD [[p5pb\|http://netbsd.gw.com/cgi-bin/man-cgi?p5pb+4.amiga+NetBSD-current]]
driver serves as an example driver implementation. It was written using the	driver serves as an example driver implementation. It was written using the
Line 135 The driver consists of several files in	Line 180 The driver consists of several files in

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).	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).

# 7. Thanks	# 8. Thanks

[[AmiBay\|http://www.amibay.com]] users d0pefish and ramborolf helped testing	[[AmiBay\|http://www.amibay.com]] users d0pefish and ramborolf helped testing
early versions of p5pb driver. Without their help this document would not	early versions of p5pb driver. Without their help this document would not

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