During host reset there is a chance that the Port number allocated by the
firmware for the attached devices may change. Also, it may be possible that
some HBA phy's can go down/come up after reset. As a result, the driver
can't just trust the HBA Port table that it has populated before host reset
as valid. Instead it has to update the HBA Port table in such a way that it
shouldn't disturb the drives which are still accessible even after host
reset.

Use the following algorithm to update the HBA Port table during host reset:

I. After host reset operation and before marking the devices as
   responding/non-responding, create a temporary Port table called "New
   Port table" by parsing each of the HBA phy's Phy data info read from SAS
   IOUnit Page0:

   a. Check whether Phy's negotiated link rate is greater than 1.5Gbps, if
      not go to next Phy;

   b. Get the SAS Address of the attached device;

   c. Create a new entry in the "New Port table" with SAS Address field
      filled with attached device's SAS Address, port number with Phy's
      Port number (read from SAS IOUnit Page0) and enable bit in the 'Phy
      mask' field corresponding to current Phy number.  New entry is
      created only if the driver can't find an entry in the "New Port
      table" which matches with attached device 'SAS Address' & 'Port
      Number'. If it finds an entry with matches with attached device 'SAS
      Address' & 'Port Number' then the driver takes that matched entry and
      will enable current Phy number bit in the 'Phy mask' field;

   d. After parsing all the HBA phy's info, the driver will have complete
      Port table info in "New Port table".

II. Mark all the existing sas_device & sas_expander device structures as
    'dirty'.

III. Mark each entry of the HBA Port lists as 'dirty'.

IV. Take each entry from 'New Port table' one by one and check whether the
    entry has any corresponding matched entry (which is marked as 'dirty')
    in the HBA Port table or not.  While looking for a corresponding
    matched entry, look for matched entry in the sequence from top row to
    bottom row listed in the following table. If you find any matched entry
    (according to any of the rules tabulated below) then perform the action
    mentioned in the 'Action' column in that matched rule.

    ===========================================================================
    |Search  |SAS     | Phy Mask | Port    | Possibilities| Action            |
    |every   |Address |    or    | Number  |              | required          |
    |entry   |matched?| subset of| matched?|              |                   |
    |in below|        | phy mask |         |              |                   |
    |sequence|        | matched? |         |              |                   |
    ===========================================================================
    |  1     |matched | matched  | matched | nothing      |* unmark HBA port  |
    |        |        |          |         | changed      |table entry as     |
    |        |        |          |         |              |dirty              |
    ---------------------------------------------------------------------------
    |  2     |matched | matched  | not     | port number  |* Update port      |
    |        |        |          | matched | is changed   |number in the      |
    |        |        |          |         |              |matched port table |
    |        |        |          |         |              |entry              |
    |        |        |          |         |              |* unmask HBA port  |
    |        |        |          |         |              |table entry as     |
    |        |        |          |         |              |dirty              |
    ---------------------------------------------------------------------------
    |  3.a   |matched | subset of| matched |some phys     |* Add these new    |
    |        |        | phy mask | (or)    |might have    |phys to current    |
    |        |        | matched  | not     |enabled which |port in STL        |
    |        |        |          | matched |are previously|* Update phy mask  |
    |        |        |          | (but    |disabled      |field in HBA's port|
    |        |        |          | first   |              |table's matched    |
    |        |        |          | look for|              |entry,             |
    |        |        |          | matched |              |* Update port      |
    |        |        |          | one)    |              |number in the      |
    |	     |	      |		 | 	   |		  |matched port       |
    |        |        |          |         |              |table entry (if    |
    |        |        |          |         |              |port number is     |
    |        |        |          |         |              |changed),          |
    |        |        |          |         |              |* Unmask HBA port  |
    |        |        |          |         |              |table entry as     |
    |        |        |          |         |              |dirty              |
    ---------------------------------------------------------------------------
    |  3.b   |matched | subset of| matched |some phys     |*Remove these phys |
    |        |        | phy mask | (or)    |might have    |from current port  |
    |        |        | matched  | not     |disabled which|in STL             |
    |        |        |          | matched |are previously|* Update phy mask  |
    |        |        |          | (but    |enabled       |field in HBA's port|
    |        |        |          | first   |              |tables's matched   |
    |        |        |          | look for|              |entry,             |
    |        |        |          | matched |              |*Update port number|
    |        |        |          | one)    |              |in the matched port|
    |        |        |          |         |              |table entry (if    |
    |        |        |          |         |              |port number is     |
    |        |        |          |         |              |changed),          |
    |        |        |          |         |              |* Unmask HBA port  |
    |        |        |          |         |              |table entry as     |
    |        |        |          |         |              |dirty              |
    ---------------------------------------------------------------------------
    |  4     |matched | not      | matched |A cable       |*Remove old phys & |
    |        |        | matched  | (or)    |attached to an|new phys to current|
    |        |        |          | not     |expander is   |port in STL        |
    |        |        |          | matched |changed to    |* Update phy mask  |
    |        |        |          |         |another HBA   |field in HBA's port|
    |        |        |          |         |port during   |tables's matched   |
    |        |        |          |         |reset         |entry,             |
    |        |        |          |         |              |*Update port number|
    |        |        |          |         |              |in the matched port|
    |        |        |          |         |              |table entry (if    |
    |        |        |          |         |              |port number is     |
    |        |        |          |         |              |changed),          |
    |        |        |          |         |              |* Unmask HBA port  |
    |        |        |          |         |              |table entry as     |
    |        |        |          |         |              |dirty              |
    ---------------------------------------------------------------------------

V. Delete the hba_port objects which are still marked as dirty.

Link: https://lore.kernel.org/r/20201027130847.9962-9-sreekanth.reddy@broadcom.comReported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>