SAS SMP PHY CONTROL function: PPTV and programmed link rate fields

Elliott, Robert (Server Storage) Elliott at hp.com
Tue Jan 21 14:34:16 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
The SAS SMP PHY CONTROL function request includes 3 major fields:
1. Phy operation (1 byte)
   Selects: NOP, Link Reset, Hard Reset, Disable,
            Clear Error Log, or Clear Affiliation
2. Partial pathway timeout value (4 bits)
3. Programmed minimum and maximum physical lnik rate (4 bits each)

sas-r03 indicates all fields are honored each time the PHY CONTROL
function is used.  However, an application shouldn't have to know the
current settings of these fields just to request an unrelated phy
operation like Clear Affiliation.

Several approaches were discussed in the SAS editor's meeting last
Friday. I'd like to resolve this in next Tuesday's conference call.
Please respond to the t10 list if you want to advocate any particular
approach.


1. New Phy Operations

Create a new Phy Operation to "Set PPTV".
Define that only Link Reset and Hard Reset operations set the programmed
link rates.

Field position options:
1a. Leave the fields in their current locations.  Avoids overlap; fewer
changes to the draft.
1b. Move the fields into a common "Phy operation-dependent data"
location.  Better prepared for new phy operations which need additional
arguments.


2. Make 0h be "maintain"

Define 0h as "maintain current setting" for the programmed link rate
fields.
Define 0h as "maintain current setting" for PPTOV; shift the meaning of
its definition so 0h=keep current setting, 1h=0 usec, 2h=1 usec, Fh=14
usec.  


3. Add "set xyz field" bits

Add "Set PPTV" and "Set Programmed Link Rates" bits in byte 11.
Regardless of Phy Operation, honor the associated fields if the
corresponding Set bit is one; ignore them if the Set bit is zero.

The DISCOVER function would return these bits in byte 11 set to 1 if the
target supports those as writable fields.


4. Other alternatives include making it more like mode pages (add a
"Report Changeable" operation and return a Changeable bit mask in the
response frame), or leaving as-is and requiring the application to put
proper values in the fields at all times.

--
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
https://ecardfile.com/id/RobElliott



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