4dbabf1049
- Add Command Completion Coalescing support. - Add SNTF support. - Add two more power management modes (4, 5), implemented on driver level. - Fix interface mode setting. - Reduce interface reset time. - Do not report meaningless protocol/transport versions. - Report CAP2 register content. - Some performance optimizations.
148 lines
5.3 KiB
Groff
148 lines
5.3 KiB
Groff
.\" Copyright (c) 2009 Alexander Motin <mav@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 24, 2009
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.Dt AHCI 4
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.Os
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.Sh NAME
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.Nm ahci
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.Nd Serial ATA Advanced Host Controller Interface driver
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following lines in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device pci"
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.Cd "device scbus"
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.Cd "device ahci"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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ahci_load="YES"
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.Ed
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.Pp
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The following tunables are settable from the loader:
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.Bl -ohang
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.It Va hint.ahci.X.msi
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controls Message Signaled Interrupts (MSI) usage by the specified controller
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.Bl -tag -compact
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.It 0
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MSI disabled;
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.It 1
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single MSI vector used, if supported (default);
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.It 2
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multiple MSI vectors used, if supported;
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.El
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.It Va hint.ahci.X.ccc
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controls Command Completion Coalescing (CCC) usage by the specified controller.
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Non-zero value enables CCC and defines maximum time (in ms), request can wait
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for interrupt, if there are some more requests present on controller queue.
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CCC reduces number of context switches on systems with many parallel requests,
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but it can decrease disk performance on some workloads due to additional
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command latency.
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.It Va hint.ahcich.X.pm_level
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controls SATA interface Power Management for specified channel,
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allowing some power to be saved at the cost of additional command
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latency.
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Possible values:
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.Bl -tag -compact
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.It 0
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interface Power Management is disabled (default);
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.It 1
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device is allowed to initiate PM state change, host is passive;
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.It 2
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host initiates PARTIAL PM state transition every time port becomes idle;
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.It 3
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host initiates SLUMBER PM state transition every time port becomes idle.
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.It 4
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driver initiates PARTIAL PM state transition 1ms after port becomes idle;
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.It 5
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driver initiates SLUMBER PM state transition 125ms after port becomes idle.
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.El
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Some controllers, such as ICH8, do not implement modes 2 and 3 with NCQ used.
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Because of artificial entering latency, performance degradation in modes
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4 and 5 is much smaller then in modes 2 and 3.
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.Pp
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Note that interface Power Management is not compatible with
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device presence detection.
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You will have to reset bus manually on device hot-plug.
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.It Va hint.ahcich.X.sata_rev
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setting to nonzero value limits maximum SATA revision (speed).
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Values 1, 2 and 3 are respectively 1.5, 3 and 6Gbps.
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.El
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.Sh DESCRIPTION
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This driver provides the CAM subsystem with native access to the
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.Tn SATA
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ports of AHCI-compatible controllers.
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Each SATA port found is represented to CAM as a separate bus with one
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target, or, if HBA supports Port Multipliers, 16 targets.
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Most of the bus-management details are handled by the SATA-specific
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transport of CAM.
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Connected ATA disks are handled by the ATA protocol disk peripheral driver
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.Xr ada 4 .
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ATAPI devices are handled by the SCSI protocol peripheral drivers
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.Xr cd 4 ,
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.Xr da 4 ,
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.Xr sa 4 ,
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etc.
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.Pp
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Driver features include support for Serial ATA and ATAPI devices,
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Port Multipliers, hardware command queues (up to 32 commands per port),
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Native Command Queuing, SATA interface Power Management, device hot-plug
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and Message Signaled Interrupts.
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.Pp
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The Port Multiplier FIS Based Switching feature added in the AHCI 1.2
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specification, which is required for effective parallel operation of devices
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behind Port Multipliers, is not yet supported.
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.Pp
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AHCI hardware is also supported by ataahci driver from
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.Xr ata 4
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subsystem. If both drivers are loaded at the same time, this one will be
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given precedence as the more functional of the two.
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.Sh HARDWARE
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The
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.Nm
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driver supports AHCI compatible controllers having PCI class 1 (mass storage),
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subclass 6 (SATA) and programming interface 1 (AHCI).
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.Sh SEE ALSO
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.Xr ada 4 ,
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.Xr cd 4 ,
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.Xr da 4 ,
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.Xr sa 4 ,
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.Xr scsi 4 ,
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.Xr ata 4
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.Sh HISTORY
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The
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.Nm
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driver first appeared in
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.Fx 8.0 .
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.Sh AUTHORS
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.An Alexander Motin Aq mav@FreeBSD.org .
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