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jamey.hick |
//This is a simple round robin memory scheduler. It's kind of bad because it's a CAM, but hey, don't have so many clients
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package mkPriorityRoundRobinMemScheduler;
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import MemControllerTypes::*;
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import IMemScheduler::*;
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import Vector::*;
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module mkPriorityRoundRobinMemScheduler (IMemScheduler#(number_clients, address_type))
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provisos
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(Bits#(address_type, addr_p),
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Eq#(address_type),
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Bits#(MemReqType#(address_type), mem_req_type_p),
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Eq#(MemReqType#(address_type))
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);
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Reg#(Bit#((TAdd#(1, TLog#(number_clients))))) first_index <- mkReg(0);
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function Bit#(TAdd#(1, TLog#(number_clients))) next_index ( Bit#(TAdd#(1, TLog#(number_clients))) curr_index );
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next_index = (curr_index < fromInteger(valueof(number_clients) - 1)) ? (curr_index + 1):(0);
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endfunction: next_index
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function Bit#(TAdd#(1, TLog#(number_clients))) prev_index ( Bit#(TAdd#(1, TLog#(number_clients))) curr_index );
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prev_index = (curr_index > 0) ? (curr_index - 1):(fromInteger(valueof(number_clients) - 1));
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endfunction: prev_index
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method ActionValue#(Maybe#(Bit#(TAdd#(1, TLog#(number_clients))))) choose_client(Vector#(number_clients, MemReqType#(address_type)) req_vec);
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Maybe#(Bit#(TAdd#(1,(TLog#(number_clients))))) target_index = tagged Invalid;
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PRIORITY_LEVEL prio = 0; //The lowest priority
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// Loop through command indicies backwards... this enables us to get the highest priority
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// command.
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for(Bit#((TAdd#(1, TLog#(number_clients)))) curr_index = prev_index(first_index), int count = 0;
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count < fromInteger(valueof(number_clients));
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curr_index = prev_index(curr_index), count = count + 1)
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begin
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if(req_vec[curr_index].req != tagged Nop)
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begin
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if(target_index matches tagged Valid .op )
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begin
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if(req_vec[curr_index].prio >= prio)
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begin
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target_index = tagged Valid curr_index;
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prio = req_vec[curr_index].prio;
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end
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end
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else
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begin
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target_index = tagged Valid curr_index;
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prio = req_vec[curr_index].prio;
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end
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end
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end
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// set the next "high priority" index.
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if(target_index matches tagged Valid .v)
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begin
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first_index <= next_index(v);
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end
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return target_index;
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endmethod
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endmodule
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endpackage
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