From: Eddie Hung <eddie@fpgeh.com>
Date: Fri, 20 Sep 2019 04:57:11 +0000 (-0700)
Subject: Update doc for ice40_dsp
X-Git-Tag: working-ls180~1039^2~69
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=34f9a8ceb285b6b59f24f994d3a877d5f4f09572;p=yosys.git

Update doc for ice40_dsp
---

diff --git a/passes/pmgen/ice40_dsp.cc b/passes/pmgen/ice40_dsp.cc
index ed3577400..2d264a6d1 100644
--- a/passes/pmgen/ice40_dsp.cc
+++ b/passes/pmgen/ice40_dsp.cc
@@ -283,9 +283,18 @@ struct Ice40DspPass : public Pass {
 		log("\n");
 		log("    ice40_dsp [options] [selection]\n");
 		log("\n");
-		log("Map multipliers and multiply-accumulate blocks to iCE40 DSP resources.\n");
+		log("Map multipliers ($mul/SB_MAC16) and multiply-accumulate ($mul/SB_MAC16 + $add)\n");
+		log("cells into iCE40 DSP resources.\n");
 		log("Currently, only the 16x16 multiply mode is supported and not the 2 x 8x8 mode.\n");
 		log("\n");
+		log("Pack input registers (A, B, {C,D}; with optional hold/reset), pipeline registers\n");
+		log("({F,J,K,G}, H; with shared reset), output registers (O; with optional hold/reset),\n");
+		log("and post-adder into the SB_MAC16 resource.\n");
+		log("\n");
+		log("Multiply-accumulate operations using the post-adder with feedback on the {C,D}\n");
+		log("input will be folded into the DSP. In this scenario only, resetting the\n");
+		log("the accumulator to an arbitrary value can be inferred to use the {C,D} input.\n");
+		log("\n");
 	}
 	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
 	{