From: Douglas Gilbert <dgilbert@interlog.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org,
Jack Wang <jack_wang@usish.com>, Luben Tuikov <ltuikov@yahoo.com>,
Xiangliang Yu <yuxiangl@marvell.com>
Subject: Re: [PATCH v8 08/13] libsas: libsas.force_hard_reset module parameter
Date: Wed, 29 Feb 2012 17:40:54 -0500 [thread overview]
Message-ID: <4F4EA976.4010607@interlog.com> (raw)
In-Reply-To: <1330552551.8846.24.camel@dabdike>
On 12-02-29 04:55 PM, James Bottomley wrote:
> On Fri, 2012-02-10 at 00:45 -0800, Dan Williams wrote:
>> It is possible for a host to get "locked out" from talking to sata
>> devices in the domain if, for example, its sas address changes but the
>> expander topology has existing affiliations with the old address. If
>> the system is booted userspace can write to
>> /sys/class/sas_phy/<phy-X>/hard_reset to clear the affiliation, however
>> if this condition exists for the root device the module parameter can be
>> used to promote all ata resets to hard resets.
A point of order: SAS has link resets and hard resets. The
hard reset is a superset of link reset. A "link reset sequence
serves as a hard reset for SATA devices" and hence is
sufficient to reset a SATA device. To reset a SAS device
(e.g. a SAS disk) you need a SAS hard reset. Therefore a link
reset is the appropriately sized "gun" to reset a SATA device.
I have a SAS-2 expander that annoyingly powers up with the
programmed maximum physical link rate of its phys at 3 Gbps
even though its hardware maximum rate is 6 Gbps. For expander
phys connected to SAS-2 disks I can up the programmed maximum
value to 6 Gbps on the expander phy then do a link reset on
that phy. So without upsetting Linux (or any other OS) I can
switch that path from 3 Gbps to 6 Gbps. Can't do that with a
SATA disk without the OS finding out.
Also to clear a SATA affiliation you should be using a SMP
PHY CONTROL (phy_op=6) function.
Doug Gilbert
next prev parent reply other threads:[~2012-02-29 22:41 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-10 8:44 [PATCH v8 00/13] libsas error handling + discovery v8 Dan Williams
2012-02-10 8:44 ` [PATCH v8 01/13] libsas: close scsi_remove_target() vs libata-eh race Dan Williams
2012-02-10 18:32 ` Jeff Garzik
2012-02-10 19:09 ` Dan Williams
2012-02-10 8:44 ` [PATCH v8 02/13] libsas: improve debug statements Dan Williams
2012-02-10 8:44 ` [PATCH v8 03/13] libsas: async ata scanning Dan Williams
2012-02-10 18:34 ` Jeff Garzik
2012-02-10 8:45 ` [PATCH v8 04/13] libsas: set attached device type and target protocols for local phys Dan Williams
2012-02-10 8:45 ` [PATCH v8 05/13] libsas: fixup target_port_protocols for expanders that don't report sata Dan Williams
2012-02-10 8:45 ` [PATCH v8 06/13] libsas: don't recover end devices attached to disabled phys Dan Williams
2012-02-10 8:45 ` [PATCH v8 07/13] scsi_transport_sas: 'enable' phys on reset Dan Williams
2012-02-10 8:45 ` [PATCH v8 08/13] libsas: libsas.force_hard_reset module parameter Dan Williams
2012-02-29 21:55 ` James Bottomley
2012-02-29 22:40 ` Douglas Gilbert [this message]
2012-02-29 23:27 ` Dan Williams
2012-03-01 0:23 ` Douglas Gilbert
2012-03-01 0:35 ` Dan Williams
2012-02-29 23:22 ` Dan Williams
2012-03-01 14:27 ` James Bottomley
2012-02-10 8:45 ` [PATCH v8 09/13] libsas: enforce eh strategy handlers only in eh context Dan Williams
2012-02-29 22:05 ` James Bottomley
2012-03-01 0:28 ` Dan Williams
2012-03-01 14:29 ` James Bottomley
2012-03-06 19:17 ` Dan Williams
2012-02-10 8:45 ` [PATCH v8 10/13] libsas: add sas_eh_abort_handler Dan Williams
2012-02-10 8:45 ` [PATCH v8 11/13] libsas: use ->lldd_I_T_nexus_reset for ->eh_bus_reset_handler Dan Williams
2012-02-10 8:45 ` [PATCH v8 12/13] isci: use sas eh strategy handlers Dan Williams
2012-02-10 8:45 ` [PATCH v8 13/13] libsas: trim sas_task of slow path infrastructure Dan Williams
2012-02-15 1:09 ` Jack Wang
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