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AHCI(4)		       FreeBSD Kernel Interfaces Manual		       AHCI(4)

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):

	   ahci_load="YES"

     The following tunables are	settable from the loader(8):

     hint.ahci.X.msi
     controls Message Signaled Interrupts (MSI)	usage by the specified con-
     troller.

	   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 con-
     troller.  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	pas-
		 sive;
	   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 detec-
     tion.  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 repre-
     sented 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 Inter-
     rupts.

     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>.

FreeBSD	10.1			 July 25, 2012			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | HARDWARE | FILES | SEE ALSO | HISTORY | AUTHORS

Want to link to this manual page? Use this URL:
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