From: Douglas Gilbert <dgilbert@interlog.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.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 19:23:02 -0500 [thread overview]
Message-ID: <4F4EC166.4010101@interlog.com> (raw)
In-Reply-To: <CABE8wwsQdhg-LhEN=sLoZAsNpOmfMVzHCpvaW5E3A1LuXzTKkw@mail.gmail.com>
On 12-02-29 06:27 PM, Dan Williams wrote:
> On Wed, Feb 29, 2012 at 2:40 PM, Douglas Gilbert<dgilbert@interlog.com> wrote:
>> 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.
>
> At least now (with these pending patches) if you trigger a link-reset
> via the sysfs interface libsas will manage the link recovery like any
> other error-recovery initiated reset.
I can think of 4 cases for link reset. The other end
of the link is:
a) a SAS target: not error recovery situation
b) a SAS expander phy: not error recovery situation
c) a SATA device: error recovery situation
d) a SAS initiator: not sure, probably not
Doug Gilbert
next prev parent reply other threads:[~2012-03-01 0:23 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
2012-02-29 23:27 ` Dan Williams
2012-03-01 0:23 ` Douglas Gilbert [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4F4EC166.4010101@interlog.com \
--to=dgilbert@interlog.com \
--cc=James.Bottomley@hansenpartnership.com \
--cc=dan.j.williams@intel.com \
--cc=jack_wang@usish.com \
--cc=linux-ide@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=ltuikov@yahoo.com \
--cc=yuxiangl@marvell.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.