The Storage Command Line Tool (StorCLI) is the command line management software designed for the MegaRAID® product line. Here are the commands to show and set PHY layer.

storcli /cx/px|pall show

This command shows the basic PHY layer information.
Example:

# storcli64 /c0/pall show     
Controller = 0
Status = Success
Description = None

PhyInfo :
=======

-----------------------------------------------------------------------------
PhyNo SAS_Addr           Phy_Identifier Link_Speed Device_Type   Description
-----------------------------------------------------------------------------
    0 0x5F01FAF0FD39307F             52 No limit   Edge Expander -           
    1 0x5F01FAF0FD39307F             54 No limit   Edge Expander -           
...        
    6 0x5F01FAF0FD39307F             64 No limit   Edge Expander -           
    7 0x5F01FAF0FD39307F             66 No limit   Edge Expander -           
-----------------------------------------------------------------------------

storcli /cx/px|pall show all

This command shows all the PHY layer information.

# storcli64 /c0/p0 show all
Controller = 0
Status = Success
Description = None

PhyInfo :
=======

-----------------------------------------------------------------------------
PhyNo SAS_Addr           Phy_Identifier Link_Speed Device_Type   Description
-----------------------------------------------------------------------------
    0 0x5F01FAF0FD39307F             52 No limit   Edge Expander -           
-----------------------------------------------------------------------------

Phy Error Counters :
==================

-----------------------------------------------------------------------
Phy_No Invld_Dwrd_Cnt Dis_Prt_Err_Cnt Ls_Dwrd_Syn_Cnt Phy_Rst_Prbl_Cnt
-----------------------------------------------------------------------
     0              0               0               0                0
-----------------------------------------------------------------------

Invld_Dwrd_Cnt=Invalid DWord Count|
Dis_Prt_Err_Cnt=Running Disparity Error Count|
Ls_Dwrd_Syn_Cnt=Loss of DWord Synch Count|
Phy_Rst_Prbl_Cnt=Phy Reset problem Count|

storcli /cx/px|pall set linkspeed=0(auto)|1.5|3|6|12

This command sets the PHY link speed. You can set the speed to 1.5 Gb/s, 3 Gb/s, 6 Gb/s, or 12 Gb/s. The linkspeed is set to auto when you specify linkspeed = 0.
Example:

storcli /c0/p0 set linkspeed=12