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2020-01-20Updated microcode source to match the changes made to general worker module.Pavel V. Shatov (Meister)
2020-01-20Cosmetic fix that only involves debug output during simulation.Pavel V. Shatov (Meister)
2020-01-20Added two pairs of new wrappers.Pavel V. Shatov (Meister)
2020-01-20Removed old DSP wrappers.Pavel V. Shatov (Meister)
2020-01-20 * DSP slices now have two use modes: MULT and ADD/SUBPavel V. Shatov (Meister)
* cosmetic rename of Verilog include file
2020-01-16This commit modifies the REGULAR_ADD_UNEVEN micro-operation to use DSP slicesPavel V. Shatov (Meister)
for addition instead of fabric logic. This opcode is only necessary when in CRT mode and is executed once per entire exponentiation to recombine the two "easier" exponentiations. This was the final change necessary to get rid of using fabric math in the general worker module.
2020-01-16Reworked modular subtraction micro-operation. Previously it used "two-pass"Pavel V. Shatov (Meister)
bank address space sweep, during the first pass (a-b) and (a-b+n) were computed, during the second pass either the former or the latter quantity was written to the output bank (depending on the very last borrow flag value). This is no longer possible, since the FSM now only generates one "interleaved" address space sweep. The solution is to split one complex modular subtraction operation into simpler sub-operations. Currently modular subtraction is achieved by running a sequence of three micro-operations: * MODULAR_SUBTRACT_X computes (a-b) and latches the final borrow flag * MODULAR_SUBTRACT_Y computes (a-b+n) * MODULAR_SUBTRACT_Z writes either (a-b) or (a-b+n) into the output bank depending on the latched value of the borrow flag Unfortunately we can't compute both (a-b) and (a-b+n) during one address space sweep, since fully pipelined adder/subtractor DSP slice has 2-cycle latency.
2020-01-16Turns out, fabric addition and subtraction in the general worker module arePavel V. Shatov (Meister)
actually in the critical paths of the ModExpNG core and are plaguing the place and route tools. I was barely able to achieve timing closure at 180 MHz even with the highest Map and PaR effort levels. This means that any further clock frequency increase is effectively impossible, moreover any small change in the design may prevent it from meeting timing constants. The obvious solution is to use DSP slices not only for modular multiplication, but also for supporting math operations. When fully pipelined, they can be clocked even faster then the block memory, so there definitely should not be any timing problems with them. The general worker module does three things that currently involve fabric-based math operations: * carry propagation (conversion to non-redundant repsesentation) * modular subtraction * regular addition This commit adds four DSP slice instances and makes the carry propagation opcode use DSP slice products instead of fabric logic.
2020-01-16Had to rework the general worker module to reach 180 MHz core clock. The modulePavel V. Shatov (Meister)
is responsible for doing certain supporting operations (mostly moving operands between banks and doing some simple math operations, such as modular subtraction and regular addition). Depending on the particular operation, one of three bank address space sweep patterns was used: * one-pass (for things like carry propagation) * two-pass (for things like modular subtraction that produce intermediate values in the process) * one-pass interleaved (for copying when only either CRT_?.X or CRT_?.Y is rewritten: we can only write to X and Y simultaneously, so we have to interleave reads from the source bank with reads from the destination bank and overwrite the destination with its just read value, otherwise the second destination operand is lost) I initially coded three FSMs, one for each of the address space sweeps and triggered one of them depending on the opcode, but that turned out too complicated. There's now only one FSM that always does the "one-pass interleaved" pattern, whereas the second read (from the destination bank) is inhibited when not need by the opcode.
2019-11-20Small change to the reductor module to try to get past 180 MHz. Previously BRAMPavel V. Shatov (Meister)
outputs were going directry into a LUT-based ternary adder which was causing timing problems. Added a layer of flip-flops, so instead of BRAM -> LUT -> FF we have BRAM -> FF -> LUT -> FF. This increases core latency by (number_of_supporting_modular_multiplications + number_of_exponent_bits) ticks.
2019-11-19Removed the latch accidentally created while pipelining the uOP engine module.Pavel V. Shatov (Meister)
The FSM previously had four states encoded using two bits, so the next state logic didn't have a default case, since all the possible states were used. Addition of the fifth state required one more state bit, so the FSM now has five states out eight possible and a default case is thus necessary.
2019-11-18Refactored reductor module.Pavel V. Shatov (Meister)
2019-11-16The uOP engine didn't compile at 180 MHz. The pipeline had two stages: FETCHPavel V. Shatov (Meister)
and DECODE. Apparently one clock cycle is not enough to entirely decode an instruction, so decoding now takes two clock cycles (DECODE_1 and DECODE_2). This seems to solve the problem. If we run into more timing violations here, we can add an extra DECODE_3 cycle and register the currently combinatorial uop_opcode_* flags at DECODE_2. This fix increases the core's latency by 59/32 clock cycles (CRT/non-CRT mode) plus two extra clock cycles per each bit of the exponent.
2019-10-23Added missing copyright headers.Pavel V. Shatov (Meister)
2019-10-23Fixed port width mismatch warning.Pavel V. Shatov (Meister)
2019-10-23Added simulation-only code to measure multiplier load.Pavel V. Shatov (Meister)
2019-10-21Reworked testbench, clk_sys and clk_core can now have any ratio, notPavel V. Shatov (Meister)
necessarily 1:2. Fixed compile-time issue where ISE fails to place two DSP slices next to each other, if A and/or B cascade path(s) between then are partially connected. Basically, if cascade is used, entire bus must be connected.
2019-10-21Further work:Pavel V. Shatov (Meister)
- added core wrapper - fixed module resets across entire core (all the resets are now consistently active-low) - continued refactoring
2019-10-21Added support for non-CRT mode. Further refactoring.Pavel V. Shatov (Meister)
2019-10-21Redesigned the testbench. Core clock does not necessarily need to be twicePavel V. Shatov (Meister)
faster than the bus clock now. It can be the same, or say four times faster.
2019-10-21Entire CRT signature algorithm works by now.Pavel V. Shatov (Meister)
Moved micro-operations handler into a separate module file, this way we don't have any synthesized stuff in the top-level module, just instantiations. This is more consistent from the design partitioning point of view. Btw, Xilinx claims their tools work better that way too, but who knows... Added optional simulation-only code to assist debugging. Un-comment the ENABLE_DEBUG `define in 'rtl/modexpng_parameters.vh' to use, but don't ever try to synthesize the core with debugging enabled.
2019-10-21Added the regular (not modular) addition operation required during the finalPavel V. Shatov (Meister)
step of the Garner's formula algorithm. Note, that the addition is "uneven" in the sense, that the first operand is full-size (as wide as the modulus), while the second one is only half the size. The adder internally banks the second input port during the second half of the addition.
2019-10-21Added "MERGE_LH" micro-operation. To be able to do Garner's formula we needPavel V. Shatov (Meister)
regular (not modular) multiplication. We're doing this by telling the modular multiplier to stop after the "square" step, which computes A*B. The problem is that the multiplier stores the lower part of the product in the internal bank L and the upper part in the internal bank H, but we need to be able to do operations on the product as a whole. MERGE_LH that combines the two halves of the product into one bank.
2019-10-21Refactored general worker modulePavel V. Shatov (Meister)
Added modular subtraction micro-operation
2019-10-03Added more micro-operations, entire Montgomery exponentiation ladder works now.Pavel V. Shatov (Meister)
2019-10-03Added more micro-operations, also added "general worker" module. The worker ↵Pavel V. Shatov (Meister)
is basically a block memory data mover, but it can also do some supporting operations required for the Garner's formula part of the exponentiation.
2019-10-03Expanded micro-operation parameters (added dedicated control bit to force ↵Pavel V. Shatov (Meister)
the B input of the modular multiplier to 1, this is necessary to bring numbers out of Montgomery domain).
2019-10-03Reworked storage architecture (moved I/O memory to a separate module, since ↵Pavel V. Shatov (Meister)
there's only one instance of input/output values, while storage manager has dual storage space for P and Q multipliers). Started working on microcoded layer, added input operation and modular multiplication.
2019-10-03Redesigned storage modules, added top-level module, added I/O storage space.Pavel V. Shatov (Meister)
2019-10-01Redesigned core architecture, unified bank structure. All storage blocks nowPavel V. Shatov (Meister)
have eight 4kbit entries and occupy one 36K BRAM tile.
2019-10-01Major rewrite (different core hierarchy, buses, wrappers, etc).Pavel V. Shatov (Meister)
2019-10-01Implemented the final stage of the Montgomery modular multiplication, i.e.Pavel V. Shatov (Meister)
addition of AB and M then reduction by right-shift.
2019-10-01Further work on the Montgomery modular multiplier. Added the thirdPavel V. Shatov (Meister)
"rectangular" stage of the multiplication process, i.e. computation of how many copies of the modulus N to add to the intermediate product AB to zeroize the lower half: M = Q * N.
2019-10-01Further work on the Montgomery modular multiplier. Can now to the "triangular"Pavel V. Shatov (Meister)
part of multiplication, i.e. compute the "magic" reduction coefficient Q = LSB(AB) * N_COEFF.
2019-10-01Started working on the pipelined Montgomery modular multiplier. Currently canPavel V. Shatov (Meister)
do the "square" part of the multiplication, i.e. compute the twice larger intermediate product AB = A * B.