Jaguar ATX

From LinuxMIPS
Jump to navigationJump to search

General Information

Commit 599ca0fb639ba843da46c3ad1a53590763539750
Date 2007-05-09 (after the 2.6.21 release)
Jaguar ATX support removed
Commit 3dedafcc0cdb8c1c56bae5ff8ded0b3fd398d13f
Date 2007-05-09 (after the 2.6.18 release)

Momentum Jaguar ATX board has a RM9000 processor (internal name Gemini) . This can be single core or dual core. The board has a Marvell Discovery II (MV64340) system controller. Newer versions of the board have a Marvell Discovery III (MV64440) system controller. This new board is called Jaguar-3.

Block Diagram

A detailed block diagram can be found at:

Detailed Description

The board supports upto 384 MB memory with 128 MB supported by the Discovery controller and 256 MB supported by the Rm9000 core. The Discovery controller has three onboard Gigabit Ethernet interfaces, two PCI busses (2 64-bit PCI slots and 2 32-bit PCI slots), serial port (16550 compatible). The board also has a HyperTransport interface.

This board is supported in Linux 2.4 and 2.6 versions (32-bit and 64-bit). The Hypertransport interface is compatible with Alliance Natasha/Sipacket HT-to-PCI-X bridge and the PLX HT-to-PCI-X bridges.

Board Limitations

The board has a complicated DMA architecture. The Discovery system controller is connected to the Rm9000 processor over the SysAD bus. The Discovery controller cannot be a master on this bus. Hence, the Discovery IO devices can only DMA data to the Discovery memory (128 MB). If the board is configured to use 384 MB memory, then the Rm9000 256 MB memory cannot be used by the Discovery controller. The board can operate in the following configurations:

1. 128 MB memory. Use the Discovery memory

2. 384 MB memory. DMA data in the 128 MB Discovery memory has to be moved to the 256 MB Rm9000 memory and vice-versa. One of the methods used in 2.4 Linux was putting the entire dmable memory into ZONE_DMA but this did require modification of many drivers and I/O subsubsystems so wasn't really acceptable.

3. All RM9000 memory configured as highmem. This is the solution used in Linux 2.6. It's the preferable way of doing things because it's consistant with the published internal Linux APIs and doesn't require extensive modifcations. This feature used to be called CONFIG_LIMITED_DMA and the Jaguar ATX was its only user. Therefore it has also been removed when Jaguar ATX support was removed.

Linux support

Supported in Linux 2.4 and 2.6 but suffering from bitrot. The odd DMA restrictions make the board hard to support in Linux and result in the need to maintain an old feature of the generic memory managment which by itself was already scheduled for removal. The board became obsolete also through the availability of supperior SOCs by RM9000 maker PMC-Sierra.