On 01/06/2018 02:21, Jason Yan wrote:
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.
Fine, it seems the tricky part here is to figure out when to issue the
linkrate change request.
