NAME¶
ahci
—
Serial ATA Advanced Host Controller Interface
driver
SYNOPSIS¶
To compile this driver into the kernel, place the following lines in your kernel
configuration file:
device pci
device scbus
device ahci
Alternatively, to load the driver as a module at boot time, place the following
line in
loader.conf(5):
The following tunables are settable from the
loader(8):
- hint.ahci.X.msi
- controls Message Signaled Interrupts (MSI) usage by the specified
controller.
- 0
- MSI disabled;
- 1
- single MSI vector used, if supported (default);
- 2
- multiple MSI vectors used, if supported;
- hint.ahci.X.ccc
- controls Command Completion Coalescing (CCC) usage by the specified
controller. Non-zero value enables CCC and defines maximum time (in ms),
request can wait for interrupt, if there are some more requests present on
controller queue. CCC reduces number of context switches on systems with
many parallel requests, but it can decrease disk performance on some
workloads due to additional command latency.
- hint.ahcich.X.pm_level
- controls SATA interface Power Management for the specified channel,
allowing some power to be saved at the cost of additional command latency.
Possible values:
- 0
- interface Power Management is disabled (default);
- 1
- device is allowed to initiate PM state change, host is passive;
- 2
- host initiates PARTIAL PM state transition every time port becomes
idle;
- 3
- host initiates SLUMBER PM state transition every time port becomes
idle.
- 4
- driver initiates PARTIAL PM state transition 1ms after port becomes
idle;
- 5
- driver initiates SLUMBER PM state transition 125ms after port becomes
idle.
Some controllers, such as ICH8, do not implement modes 2 and 3 with NCQ
used. Because of artificial entering latency, performance degradation in
modes 4 and 5 is much smaller then in modes 2 and 3.
Note that interface Power Management complicates device presence detection.
A manual bus reset/rescan may be needed after device hot-plug, unless
hardware implements Cold Presence Detection.
- hint.ahcich.X.sata_rev
- setting to nonzero value limits maximum SATA revision (speed). Values 1, 2
and 3 are respectively 1.5, 3 and 6Gbps.
- hw.ahci.force
- setting to nonzero value forces driver attach to some known AHCI-capable
chips even if they are configured for legacy IDE emulation. Default is
1.
DESCRIPTION¶
This driver provides the
CAM(4) subsystem with
native access to the SATA ports of AHCI-compatible controllers. Each SATA port
found is represented to CAM as a separate bus with one target, or, if HBA
supports Port Multipliers, 16 targets. Most of the bus-management details are
handled by the SATA-specific transport of CAM. Connected ATA disks are handled
by the ATA protocol disk peripheral driver
ada(4). ATAPI devices are handled by the SCSI
protocol peripheral drivers
cd(4),
da(4),
sa(4), etc.
Driver features include support for Serial ATA and ATAPI devices, Port
Multipliers (including FIS-based switching, when supported), hardware command
queues (up to 32 commands per port), Native Command Queuing, SATA interface
Power Management, device hot-plug and Message Signaled Interrupts.
Driver supports "LED" enclosure management messages, defined by the
AHCI. When supported by hardware, it allows to control per-port activity,
locate and fault LEDs via the
led(4) API or
emulated
ses(4) device for localization and
status reporting purposes. Supporting AHCI controllers may transmit that
information to the backplane controllers via SGPIO interface. Backplane
controllers interpret received statuses in some way (IBPI standard) to report
them using present indicators.
AHCI hardware is also supported by ataahci driver from
ata(4) subsystem. If both drivers are loaded at
the same time, this one will be given precedence as the more functional of the
two.
HARDWARE¶
The
ahci
driver supports AHCI compatible
controllers having PCI class 1 (mass storage), subclass 6 (SATA) and
programming interface 1 (AHCI).
Also, in cooperation with atamarvell and atajmicron drivers of
ata(4), it
supports AHCI part of legacy-PATA + AHCI-SATA combined controllers, such as
JMicron JMB36x and Marvell 88SE61xx.
FILES¶
- /dev/led/ahci*.*.act
- activity LED device nodes
- /dev/led/ahci*.*.fault
- fault LED device nodes
- /dev/led/ahci*.*.locate
- locate LED device nodes
SEE ALSO¶
ada(4),
ata(4),
cam(4),
cd(4),
da(4),
sa(4),
ses(4)
HISTORY¶
The
ahci
driver first appeared in
FreeBSD 8.0.
AUTHORS¶
Alexander Motin
⟨mav@FreeBSD.org⟩.