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/share/man/man4/ahci.4

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  1.\" Copyright (c) 2009-2012 Alexander Motin <mav@FreeBSD.org>
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 25.\" $FreeBSD$
 26.\"
 27.Dd July 25, 2012
 28.Dt AHCI 4
 29.Os
 30.Sh NAME
 31.Nm ahci
 32.Nd Serial ATA Advanced Host Controller Interface driver
 33.Sh SYNOPSIS
 34To compile this driver into the kernel,
 35place the following lines in your
 36kernel configuration file:
 37.Bd -ragged -offset indent
 38.Cd "device pci"
 39.Cd "device scbus"
 40.Cd "device ahci"
 41.Ed
 42.Pp
 43Alternatively, to load the driver as a
 44module at boot time, place the following line in
 45.Xr loader.conf 5 :
 46.Bd -literal -offset indent
 47ahci_load="YES"
 48.Ed
 49.Pp
 50The following tunables are settable from the
 51.Xr loader 8 :
 52.Bl -ohang
 53.It Va hint.ahci. Ns Ar X Ns Va .msi
 54controls Message Signaled Interrupts (MSI) usage by the specified controller.
 55.Pp
 56.Bl -tag -width 4n -offset indent -compact
 57.It 0
 58MSI disabled;
 59.It 1
 60single MSI vector used, if supported (default);
 61.It 2
 62multiple MSI vectors used, if supported;
 63.El
 64.It Va hint.ahci. Ns Ar X Ns Va .ccc
 65controls Command Completion Coalescing (CCC) usage by the specified controller.
 66Non-zero value enables CCC and defines maximum time (in ms), request can wait
 67for interrupt, if there are some more requests present on controller queue.
 68CCC reduces number of context switches on systems with many parallel requests,
 69but it can decrease disk performance on some workloads due to additional
 70command latency.
 71.It Va hint.ahcich. Ns Ar X Ns Va .pm_level
 72controls SATA interface Power Management for the specified channel,
 73allowing some power to be saved at the cost of additional command
 74latency.
 75Possible values:
 76.Pp
 77.Bl -tag -width 4n -offset indent -compact
 78.It 0
 79interface Power Management is disabled (default);
 80.It 1
 81device is allowed to initiate PM state change, host is passive;
 82.It 2
 83host initiates PARTIAL PM state transition every time port becomes idle;
 84.It 3
 85host initiates SLUMBER PM state transition every time port becomes idle.
 86.It 4
 87driver initiates PARTIAL PM state transition 1ms after port becomes idle;
 88.It 5
 89driver initiates SLUMBER PM state transition 125ms after port becomes idle.
 90.El
 91.Pp
 92Some controllers, such as ICH8, do not implement modes 2 and 3 with NCQ used.
 93Because of artificial entering latency, performance degradation in modes
 944 and 5 is much smaller then in modes 2 and 3.
 95.Pp
 96Note that interface Power Management complicates device presence detection.
 97A manual bus reset/rescan may be needed after device hot-plug, unless hardware
 98implements Cold Presence Detection.
 99.It Va hint.ahcich. Ns Ar X Ns Va .sata_rev
100setting to nonzero value limits maximum SATA revision (speed).
101Values 1, 2 and 3 are respectively 1.5, 3 and 6Gbps.
102.It Va hw.ahci.force
103setting to nonzero value forces driver attach to some known AHCI-capable
104chips even if they are configured for legacy IDE emulation.
105Default is 1.
106.El
107.Sh DESCRIPTION
108This driver provides the
109.Xr CAM 4
110subsystem with native access to the
111.Tn SATA
112ports of AHCI-compatible controllers.
113Each SATA port found is represented to CAM as a separate bus with one
114target, or, if HBA supports Port Multipliers, 16 targets.
115Most of the bus-management details are handled by the SATA-specific
116transport of CAM.
117Connected ATA disks are handled by the ATA protocol disk peripheral driver
118.Xr ada 4 .
119ATAPI devices are handled by the SCSI protocol peripheral drivers
120.Xr cd 4 ,
121.Xr da 4 ,
122.Xr sa 4 ,
123etc.
124.Pp
125Driver features include support for Serial ATA and ATAPI devices,
126Port Multipliers (including FIS-based switching, when supported),
127hardware command queues (up to 32 commands per port),
128Native Command Queuing, SATA interface Power Management, device hot-plug
129and Message Signaled Interrupts.
130.Pp
131Driver supports "LED" enclosure management messages, defined by the AHCI.
132When supported by hardware, it allows to control per-port activity, locate
133and fault LEDs via the
134.Xr led 4
135API or emulated
136.Xr ses 4
137device for localization and status reporting purposes.
138Supporting AHCI controllers may transmit that information to the backplane
139controllers via SGPIO interface. Backplane controllers interpret received
140statuses in some way (IBPI standard) to report them using present indicators.
141.Pp
142AHCI hardware is also supported by ataahci driver from
143.Xr ata 4
144subsystem.
145If both drivers are loaded at the same time, this one will be
146given precedence as the more functional of the two.
147.Sh HARDWARE
148The
149.Nm
150driver supports AHCI compatible controllers having PCI class 1 (mass storage),
151subclass 6 (SATA) and programming interface 1 (AHCI).
152.Pp
153Also, in cooperation with atamarvell and atajmicron drivers of ata(4),
154it supports AHCI part of legacy-PATA + AHCI-SATA combined controllers,
155such as JMicron JMB36x and Marvell 88SE61xx.
156.Sh FILES
157.Bl -tag -width /dev/led/ahcich*.locate
158.It Pa /dev/led/ahci*.*.act
159activity LED device nodes
160.It Pa /dev/led/ahci*.*.fault
161fault LED device nodes
162.It Pa /dev/led/ahci*.*.locate
163locate LED device nodes
164.El
165.Sh SEE ALSO
166.Xr ada 4 ,
167.Xr ata 4 ,
168.Xr cam 4 ,
169.Xr cd 4 ,
170.Xr da 4 ,
171.Xr sa 4 ,
172.Xr ses 4
173.Sh HISTORY
174The
175.Nm
176driver first appeared in
177.Fx 8.0 .
178.Sh AUTHORS
179.An Alexander Motin Aq mav@FreeBSD.org .