xref: /freebsd/share/man/man4/ahci.4 (revision a5921bc3653e2e286715e6fe8d473ec0d02da38c)
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25.\" $FreeBSD$
26.\"
27.Dd October 22, 2013
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;
61.It 2
62multiple MSI vectors used, if supported (default);
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.ahci. Ns Ar X Ns Va .direct
72controls whether the driver should use direct command completion from
73interrupt thread(s), or queue them to CAM completion threads.
74Default value depends on number of MSI interrupts supported and number of
75implemented SATA ports.
76.It Va hint.ahcich. Ns Ar X Ns Va .pm_level
77controls SATA interface Power Management for the specified channel,
78allowing some power to be saved at the cost of additional command
79latency.
80Possible values:
81.Pp
82.Bl -tag -width 4n -offset indent -compact
83.It 0
84interface Power Management is disabled (default);
85.It 1
86device is allowed to initiate PM state change, host is passive;
87.It 2
88host initiates PARTIAL PM state transition every time port becomes idle;
89.It 3
90host initiates SLUMBER PM state transition every time port becomes idle.
91.It 4
92driver initiates PARTIAL PM state transition 1ms after port becomes idle;
93.It 5
94driver initiates SLUMBER PM state transition 125ms after port becomes idle.
95.El
96.Pp
97Some controllers, such as ICH8, do not implement modes 2 and 3 with NCQ used.
98Because of artificial entering latency, performance degradation in modes
994 and 5 is much smaller then in modes 2 and 3.
100.Pp
101Note that interface Power Management complicates device presence detection.
102A manual bus reset/rescan may be needed after device hot-plug, unless hardware
103implements Cold Presence Detection.
104.It Va hint.ahcich. Ns Ar X Ns Va .sata_rev
105setting to nonzero value limits maximum SATA revision (speed).
106Values 1, 2 and 3 are respectively 1.5, 3 and 6Gbps.
107.It Va hw.ahci.force
108setting to nonzero value forces driver attach to some known AHCI-capable
109chips even if they are configured for legacy IDE emulation.
110Default is 1.
111.El
112.Sh DESCRIPTION
113This driver provides the
114.Xr CAM 4
115subsystem with native access to the
116.Tn SATA
117ports of AHCI-compatible controllers.
118Each SATA port found is represented to CAM as a separate bus with one
119target, or, if HBA supports Port Multipliers, 16 targets.
120Most of the bus-management details are handled by the SATA-specific
121transport of CAM.
122Connected ATA disks are handled by the ATA protocol disk peripheral driver
123.Xr ada 4 .
124ATAPI devices are handled by the SCSI protocol peripheral drivers
125.Xr cd 4 ,
126.Xr da 4 ,
127.Xr sa 4 ,
128etc.
129.Pp
130Driver features include support for Serial ATA and ATAPI devices,
131Port Multipliers (including FIS-based switching, when supported),
132hardware command queues (up to 32 commands per port),
133Native Command Queuing, SATA interface Power Management, device hot-plug
134and Message Signaled Interrupts.
135.Pp
136Driver supports "LED" enclosure management messages, defined by the AHCI.
137When supported by hardware, it allows to control per-port activity, locate
138and fault LEDs via the
139.Xr led 4
140API or emulated
141.Xr ses 4
142device for localization and status reporting purposes.
143Supporting AHCI controllers may transmit that information to the backplane
144controllers via SGPIO interface. Backplane controllers interpret received
145statuses in some way (IBPI standard) to report them using present indicators.
146.Sh HARDWARE
147The
148.Nm
149driver supports AHCI compatible controllers having PCI class 1 (mass storage),
150subclass 6 (SATA) and programming interface 1 (AHCI).
151.Pp
152Also, in cooperation with atamarvell and atajmicron drivers of ata(4),
153it supports AHCI part of legacy-PATA + AHCI-SATA combined controllers,
154such as JMicron JMB36x and Marvell 88SE61xx.
155.Sh FILES
156.Bl -tag -width /dev/led/ahcich*.locate
157.It Pa /dev/led/ahci*.*.act
158activity LED device nodes
159.It Pa /dev/led/ahci*.*.fault
160fault LED device nodes
161.It Pa /dev/led/ahci*.*.locate
162locate LED device nodes
163.El
164.Sh SEE ALSO
165.Xr ada 4 ,
166.Xr ata 4 ,
167.Xr cam 4 ,
168.Xr cd 4 ,
169.Xr da 4 ,
170.Xr sa 4 ,
171.Xr ses 4
172.Sh HISTORY
173The
174.Nm
175driver first appeared in
176.Fx 8.0 .
177.Sh AUTHORS
178.An Alexander Motin Aq Mt mav@FreeBSD.org
179