Linux Drivers Page

Adaptec Aic7xxx driver

Change Log

Description

This driver provides access to the SCSI bus(es) connected to Adaptec AIC7770, AIC7850, AIC7856, AIC7860, AIC7870, AIC7880, AIC7890, AIC7891, AIC7892, AIC7895, AIC7896, AIC7897 and AIC7899 host adapter chips. These chips are found on many motherboards as well as the following Adaptec SCSI controller cards: 274X(W), 274X(T), 284X, 2902, 2904, 2906, 2910, 2915, 2920, 2930C, 2930U2, 2940, 2940U, 2940AU, 2940UW, 2940UW Dual, 2940UW Pro, 2940U2W, 2940U2B, 2950U2W, 2950U2B, 19160B, 29160B, 29160N, 3940, 3940U, 3940AU, 3940UW, 3940AUW, 3940U2W, 3950U2, 3960, 39160, 3985, and 4944UW.

Driver features include support for twin and wide busses, fast, ultra, ultra2, and double transition(U160) synchronous transfers depending on controller type, and tagged queuing. The driver can support target mode in Operating System environments such as facilities exist in the SCSI layer.

Per target configuration performed in the SCSI-Select menu, accessible at boot in non-EISA models, or through an EISA configuration utility for EISA models, is honored by this driver. This includes synchronous/asynchronous transfers, maximum synchronous negotiation rate, wide transfers, disconnection, the host adapter's SCSI ID, and, PCI controllers, the primary channel selection. For systems that store non-volatile settings in a system specific manner rather than a serial eeprom directly connected to the aic7xxx controller, the BIOS must be enabled for the driver to access this information. This restriction applies to all EISA and many motherboard configurations.

Note that I/O addresses are determined automatically by the probe routines, but care should be taken when using a 284x (VESA local bus controller) in an EISA system. The jumpers setting the I/O area for the 284x should match the EISA slot into which the card is inserted to prevent conflicts with other EISA cards.

Performance and feature sets vary throughout the aic7xxx product line. The following table provides a comparison of the different chips supported by the ahc driver. Note that wide and twin channel features, although always supported by a particular chip, may be disabled in a particular motherboard or card design.

Chip	MIPS	Bus	MaxSync	MaxWidth	SCBs	Features
aic7770	10	EISA/VL	10MHz	16Bit	4	1
aic7850	10	PCI/32	10MHz	8Bit	3
aic7860	10	PCI/32	20MHz	8Bit	3
aic7870	10	PCI/32	10MHz	16Bit	16
aic7880	10	PCI/32	20MHz	16Bit	16
aic7890	20	PCI/32	40MHz	16Bit	32	3 4 5 6 7 8
aic7891	20	PCI/64	40MHz	16Bit	32	3 4 5 6 7 8
aic7892	20	PCI/64	80MHz	16Bit	32	3 4 5 6 7 8
aic7895	10/15/20	PCI/32	20MHz	16Bit	32	2 3 4 5
aic7895C	10/15/20	PCI/32	20MHz	16Bit	32	2 3 4 5 8
aic7896	20	PCI/32	40MHz	16Bit	32	2 3 4 5 6 7 8
aic7897	20	PCI/64	40MHz	16Bit	32	2 3 4 5 6 7 8
aic7899	20	PCI/64	80MHz	16Bit	32	2 3 4 5 6 7 8

1. Multiplexed Twin Channel Device - One controller servicing two busses.
2. Multi-function Twin Channel Device - Two controllers on one chip.
3. Command Channel Secondary DMA Engine - Allows scatter gather list and SCB prefetch.
4. 64 Byte SCB Support. Standard SCB size is 32 bytes. The driver currently operates all controllers using standard sized SCBs unless external sram is available. The extra space is used to optimize untagged-I/O. By using standard sized SCBs, the number of SCBs is doubled, thereby improving performance. All SCB numbers listed for these controllers are for standard sized SCBs.
5. Block Move Instruction Support - Single instruction running at higher clock speed to move multiple bytes of data.
6. `Bayonet' style Scatter Gather Engine - Improves DMA performance by seemlessly stiching DMA across S/G boundaries.
7. Queuing Registers - Allows queuing of new transactions without pausing the sequencer.
8. Multiple Target IDs - Allows the controller to respond to se- lection as a target on multiple SCSI IDs.

Linux Driver Configuration

SCSI Control Blocks (SCBs)

Every transaction sent to a device on the SCSI bus is assigned a `SCSI Control Block' (SCB). The SCB contains all of the information required by the controller to process a transaction. The chip feature table lists the number of SCBs that can be stored in on-chip memory. All chips with model numbers greater than or equal to 7870 allow for the on chip SCB space to be augmented with external SRAM up to a maximum of 253 SCBs. Very few Adaptec controller configurations have external SRAM.

If external SRAM is not available, SCBs are a limited resource. Using the SCBs in a straight forward manner would only allow the driver to handle as many concurrent transactions as there are physical SCBs. To fully utilize the SCSI bus and the devices on it, requires much more concurrency. The solution to this problem is SCB Paging, a concept similar to memory paging. SCB paging takes advantage of the fact that devices usually disconnect from the SCSI bus for long periods of time without talking to the controller. The SCBs for disconnected transactions are only of use to the controller when the transfer is resumed. When the host queues another transaction for the controller to execute, the controller firmware will use a free SCB if one is available. Otherwise, the state of the most recently disconnected (and therefor most likely to stay disconnected) SCB is saved, via dma, to host memory, and the local SCB reused to start the new transaction. This allows the controller to queue up to 253 transactions regardless of the amount of SCB space. Since the local SCB space serves as a cache for disconnected transactions, the more SCB space available, the less host bus traffic consumed saving and restoring SCB data.

Installation

The driver is currently available in three forms: RPM, Driver Update diskettes, and as a tar file that contains only the aic7xxx driver files. The DUD and RPM methods of installation are preferred to the source method as the source tar file will not contain all of the Makefile and other system patches that are required for the driver to function.

RPM Releases

Driver Update Diskette Releases

Source File Releases