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// ========== Copyright Header Begin ==========================================

// 

// OpenSPARC T1 Processor File: lsu_rrobin_picker2.v

// Copyright (c) 2006 Sun Microsystems, Inc.  All Rights Reserved.

// DO NOT ALTER OR REMOVE COPYRIGHT NOTICES.

// 

// The above named program is free software; you can redistribute it and/or

// modify it under the terms of the GNU General Public

// License version 2 as published by the Free Software Foundation.

// 

// The above named program is distributed in the hope that it will be 

// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

// General Public License for more details.

// 

// You should have received a copy of the GNU General Public

// License along with this work; if not, write to the Free Software

// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.

// 

// ========== Copyright Header End ============================================

////////////////////////////////////////////////////////////////////////

/*

//      Description:    Round-Robin Picker for 4 eventss.

//                      (see description of picker at the end of this file)

*/

////////////////////////////////////////////////////////////////////////

// Global header file includes

////////////////////////////////////////////////////////////////////////

`include        "sys.h" // system level definition file which contains the

                                        // time scale definition

////////////////////////////////////////////////////////////////////////

// Local header file includes / local defines

////////////////////////////////////////////////////////////////////////    

module lsu_rrobin_picker2 (/*AUTOARG*/

   // Outputs

   so, pick_one_hot,

   // Inputs

   rclk, grst_l, arst_l, si, se, events, events_picked, thread_force

   );

input           rclk ;

input           grst_l;

input           arst_l;

input           si;

input           se;

output          so;

input   [3:0]    events ;                // multi-hot; events that could be chosen

input   [3:0]    events_picked ;         // one-hot; events that were picked - same cycle as pick

input   [3:0]    thread_force ;          // multi-hot; thread events that have high priority

output  [3:0]    pick_one_hot ;          // one-hot

wire         clk;

wire         reset,dbb_reset_l ;

wire  [3:0]  thread_force_pe_mask ;

wire  [3:0]  pick_thread_force_1hot ;

wire         thread_force_events_sel ;

wire  [3:0]  pick_rrobin_1hot, pick_rev_rrobin_1hot, pick_rrobin_1hot_mx ;

wire         events_pick_dir_d1 ;

wire         events_pick_dir ;

wire  [3:0]  pick_rrobin_status_or_one_hot ;

wire  [3:0]  pick_rrobin_din ;

wire  [3:0]  pick_rrobin ;

wire         pick_rrobin_reset ;

wire         pick_rrobin_dir_upd ;

wire  [3:0]  pick_rrobin_events ;

    dffrl_async rstff(.din (grst_l),

                        .q   (dbb_reset_l),

                        .clk (clk), .se(se), .si(), .so(),

                        .rst_l (arst_l));

assign  reset =  ~dbb_reset_l;

assign  clk = rclk;

//*******************************************************************************************************

//PICK  

//*******************************************************************************************************

   //pick for thread force events

assign  thread_force_events_sel = |(events[3:0] & thread_force[3:0]) ;

assign  thread_force_pe_mask[3:0]  =  events[3:0] & thread_force[3:0] ;

assign  pick_thread_force_1hot[0] = thread_force_pe_mask[0] ;

assign  pick_thread_force_1hot[1] = thread_force_pe_mask[1] & ~thread_force_pe_mask[0] ;

assign  pick_thread_force_1hot[2] = thread_force_pe_mask[2] & ~|thread_force_pe_mask[1:0] ;

assign  pick_thread_force_1hot[3] = thread_force_pe_mask[3] & ~|thread_force_pe_mask[2:0] ;

   //pick for round robin events

assign  pick_rrobin_events[3:0]  =  events[3:0] & ~pick_rrobin[3:0] ;

assign  pick_rrobin_1hot[0] = ~events_pick_dir_d1 & pick_rrobin_events[0] ;

assign  pick_rrobin_1hot[1] = ~events_pick_dir_d1 & pick_rrobin_events[1] & ~pick_rrobin_events[0] ;

assign  pick_rrobin_1hot[2] = ~events_pick_dir_d1 & pick_rrobin_events[2] & ~|pick_rrobin_events[1:0] ;

assign  pick_rrobin_1hot[3] = ~events_pick_dir_d1 & pick_rrobin_events[3] & ~|pick_rrobin_events[2:0] ;

   //pick for reverse round robin events

assign  pick_rev_rrobin_1hot[0] = events_pick_dir_d1 & pick_rrobin_events[0] & ~|pick_rrobin_events[3:1] ;

assign  pick_rev_rrobin_1hot[1] = events_pick_dir_d1 & pick_rrobin_events[1] & ~|pick_rrobin_events[3:2] ;

assign  pick_rev_rrobin_1hot[2] = events_pick_dir_d1 & pick_rrobin_events[2] & ~|pick_rrobin_events[3] ;

assign  pick_rev_rrobin_1hot[3] = events_pick_dir_d1 & pick_rrobin_events[3] ;

assign  pick_rrobin_1hot_mx[3:0]  =  pick_rev_rrobin_1hot[3:0] | pick_rrobin_1hot[3:0] ;

assign  pick_one_hot[3:0]    =  thread_force_events_sel ? pick_thread_force_1hot[3:0] :

                                                          pick_rrobin_1hot_mx[3:0] ;

//*******************************************************************************************************

//*******************************************************************************************************

//PICK ROUND ROBIN (bug4814)

//*******************************************************************************************************

// this is used if there are no requests to be picked based on pick_status[3:0]

assign pick_rrobin_status_or_one_hot[3:0] = pick_rrobin[3:0] | events_picked[3:0] ;

assign pick_rrobin_reset = reset | ~|(events[3:0] & ~pick_rrobin_status_or_one_hot[3:0]) ;

   //change direction bit only when events are non-zero

assign pick_rrobin_dir_upd = |events[3:0] & (~|(events[3:0] & ~pick_rrobin_status_or_one_hot[3:0])) ;

   // make reset dominant

assign pick_rrobin_din[3:0] = pick_rrobin_status_or_one_hot[3:0] & ~{4{pick_rrobin_reset}};

dff_s   #(4) ff_pick_rrobin (

           .din    (pick_rrobin_din[3:0]),

           .q      (pick_rrobin[3:0]    ),

           .clk    (clk),

           .se     (1'b0),       .si (),          .so ()

            );

//*******************************************************************************************************

//*******************************************************************************************************

// PICK DIRECTION

//*******************************************************************************************************

   //bug4609 - change direction of pick all events are picked in round robin pick

   //          this is needed when the condition below occurs. assuming misc is less frequent

   //          this should pick load/store in round robin fashion

   //-------------------------------------------------------

   // cycle                 0   1   2

   //-------------------------------------------------------

   // history{misc,st,ld}  010 011 011

   // vld{misc,st,ld}      011 011 011

   //-------------------------------------------------------

assign events_pick_dir  =  ~reset &

                           (( ~pick_rrobin_dir_upd & events_pick_dir_d1) |              //hold

                            (  pick_rrobin_dir_upd & ~events_pick_dir_d1)) ;            //set - invert direction

   dff_s   #(1) ff_events_pick_dir (

        .din    (events_pick_dir),

        .q      (events_pick_dir_d1),

        .clk    (clk),

        .se     (1'b0),       .si (),          .so ()

        );

//*******************************************************************************************************

endmodule