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From: Jason Yan <yanaijie@huawei.com>
To: John Garry <john.garry@huawei.com>, <martin.petersen@oracle.com>,
	<jejb@linux.vnet.ibm.com>
Cc: <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<zhaohongjiang@huawei.com>, <hare@suse.com>,
	<dan.j.williams@intel.com>, <jthumshirn@suse.de>, <hch@lst.de>,
	<huangdaode@hisilicon.com>, <chenxiang66@hisilicon.com>,
	<xiexiuqi@huawei.com>, <tj@kernel.org>, <miaoxie@huawei.com>,
	chenqilin <chenqilin2@huawei.com>, Ewan Milne <emilne@redhat.com>,
	Tomas Henzl <thenzl@redhat.com>
Subject: Re: [PATCH 8/8] scsi: libsas: support SATA phy link rate unmatch the pathway
Date: Fri, 1 Jun 2018 09:21:44 +0800	[thread overview]
Message-ID: <5B109FA8.9010402@huawei.com> (raw)
In-Reply-To: <ed533ab2-018d-0bda-568f-0034dac1e332@huawei.com>



On 2018/6/1 0:05, John Garry wrote:
> On 29/05/2018 03:23, Jason Yan wrote:
>> If a SATA disk attached to a expander phy and it's linkrate is greater
>> than the expander host phy's linkrate, the disk will failed to discover.
>> The topology is like below:
>>
>>    +----------+           +----------+
>>    |          |           |          |
>>    |          |-- 3.0 G --|          |-- 6.0 G -- SAS  disk
>>    |          |           |          |
>>    |          |-- 3.0 G --|          |-- 6.0 G -- SAS  disk
>>    |initiator |           |          |
>>    | device   |-- 3.0 G --| Expander |-- 6.0 G -- SAS  disk
>>    |          |           |          |
>>    |          |-- 3.0 G --|          |-- 6.0 G -- SATA disk  -->failed
>> to connect
>>    |          |           |          |
>>    |          |           |          |-- 6.0 G -- SATA disk  -->failed
>> to connect
>>    |          |           |          |
>>    +----------+           +----------+
>>
>> And when we check the sas protocal spec, this scenario is described as
>> this:
>>
>> 7.13 Rate matching
>> ......
>> If an expander phy attached to a SATA phy is using a physical link rate
>> greater than the maximum connection rate supported by the pathway from
>> an STP initiator port, a management application client should use the
>> SMP PHY CONTROL function (see 10.4.3.10) to set the PROGRAMMED MAXIMUM
>> PHYSICAL LINK RATE field of the expander phy to the maximum connection
>> rate supported by the pathway from that STP initiator port.
>>
>> In order to support this scenario, checking the SATA disk's linkrate
>> to see if it is greater than any phy's linkrate it may pass through.
>> Remember the minimum linkrate of the pathway and set the SATA phy
>> linkrate to it using the SMP PHY CONTROL function.
>
> As we (re)discover the tree, can we keep track of the min pathway to the
> root PHY dynamically (per expander), and then take action for any SATA
> devices attached which have a negotiated linkrate greater (than the
> expanders min pathway)? This would be an alternate to your approach of
> finishing discovery and then checking the min pathway as a whole new step.
>

Seems better, I will have a try to see if it works. Thanks.

>
> .
>

  reply	other threads:[~2018-06-01  1:22 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-29  2:23 [PATCH 0/8] libsas: Support swapping disks and SATA phy link rate matching " Jason Yan
2018-05-29  2:23 ` [PATCH 1/8] scsi: libsas: delete dead code in scsi_transport_sas.c Jason Yan
2018-05-29  7:33   ` Johannes Thumshirn
2018-05-31 14:26   ` John Garry
2018-05-29  2:23 ` [PATCH 2/8] scsi: libsas: check the lldd callback correctly Jason Yan
2018-05-29  7:34   ` Johannes Thumshirn
2018-05-31 14:09   ` John Garry
2018-06-01  0:15     ` Jason Yan
2018-05-29  2:23 ` [PATCH 3/8] scsi: libsas: always unregister the old device if going to discover new Jason Yan
2018-05-29  7:37   ` Johannes Thumshirn
2018-05-31 15:09   ` John Garry
2018-06-01  0:28     ` Jason Yan
2018-05-29  2:23 ` [PATCH 4/8] scsi: libsas: trigger a new revalidation to discover the device Jason Yan
2018-05-29  7:43   ` Johannes Thumshirn
2018-05-31 15:42   ` John Garry
2018-06-01  0:59     ` Jason Yan
2018-06-01 10:02       ` John Garry
2018-06-04  1:01         ` Jason Yan
2018-05-29  2:23 ` [PATCH 5/8] scsi: libsas: check if the same sata device when flutter Jason Yan
2018-05-29  2:23 ` [PATCH 6/8] scsi: libsas: reset the phy state and address if discover failed Jason Yan
2018-05-29  2:23 ` [PATCH 7/8] scsi: libsas: fix issue of swapping two sas disks Jason Yan
2018-05-29  2:23 ` [PATCH 8/8] scsi: libsas: support SATA phy link rate unmatch the pathway Jason Yan
2018-05-31 16:05   ` John Garry
2018-06-01  1:21     ` Jason Yan [this message]
2018-06-01 10:13       ` John Garry

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