1 .\" Copyright (c) 2009 Alexander Motin <mav@FreeBSD.org>
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33 .Nd Serial ATA Advanced Host Controller Interface driver
35 To compile this driver into the kernel,
36 place the following lines in your
37 kernel configuration file:
38 .Bd -ragged -offset indent
44 Alternatively, to load the driver as a
45 module at boot time, place the following line in
47 .Bd -literal -offset indent
51 The following tunables are settable from the loader:
53 .It Va hint.ahci.X.msi
54 controls Message Signaled Interrupts (MSI) usage by the specified controller
59 single MSI vector used, if supported (default);
61 multiple MSI vectors used, if supported;
63 .It Va hint.ahci.X.ccc
64 controls Command Completion Coalescing (CCC) usage by the specified controller.
65 Non-zero value enables CCC and defines maximum time (in ms), request can wait
66 for interrupt, if there are some more requests present on controller queue.
67 CCC reduces number of context switches on systems with many parallel requests,
68 but it can decrease disk performance on some workloads due to additional
70 .It Va hint.ahcich.X.pm_level
71 controls SATA interface Power Management for specified channel,
72 allowing some power to be saved at the cost of additional command
77 interface Power Management is disabled (default);
79 device is allowed to initiate PM state change, host is passive;
81 host initiates PARTIAL PM state transition every time port becomes idle;
83 host initiates SLUMBER PM state transition every time port becomes idle.
85 driver initiates PARTIAL PM state transition 1ms after port becomes idle;
87 driver initiates SLUMBER PM state transition 125ms after port becomes idle.
89 Some controllers, such as ICH8, do not implement modes 2 and 3 with NCQ used.
90 Because of artificial entering latency, performance degradation in modes
91 4 and 5 is much smaller then in modes 2 and 3.
93 Note that interface Power Management is not compatible with
94 device presence detection.
95 You will have to reset bus manually on device hot-plug.
96 .It Va hint.ahcich.X.sata_rev
97 setting to nonzero value limits maximum SATA revision (speed).
98 Values 1, 2 and 3 are respectively 1.5, 3 and 6Gbps.
101 This driver provides the CAM subsystem with native access to the
103 ports of AHCI-compatible controllers.
104 Each SATA port found is represented to CAM as a separate bus with one
105 target, or, if HBA supports Port Multipliers, 16 targets.
106 Most of the bus-management details are handled by the SATA-specific
108 Connected ATA disks are handled by the ATA protocol disk peripheral driver
110 ATAPI devices are handled by the SCSI protocol peripheral drivers
116 Driver features include support for Serial ATA and ATAPI devices,
117 Port Multipliers, hardware command queues (up to 32 commands per port),
118 Native Command Queuing, SATA interface Power Management, device hot-plug
119 and Message Signaled Interrupts.
121 The Port Multiplier FIS Based Switching feature added in the AHCI 1.2
122 specification, which is required for effective parallel operation of devices
123 behind Port Multipliers, is not yet supported.
125 AHCI hardware is also supported by ataahci driver from
127 subsystem. If both drivers are loaded at the same time, this one will be
128 given precedence as the more functional of the two.
132 driver supports AHCI compatible controllers having PCI class 1 (mass storage),
133 subclass 6 (SATA) and programming interface 1 (AHCI).
144 driver first appeared in
147 .An Alexander Motin Aq mav@FreeBSD.org .