axi_hdmi_tx: Add parameter to configure the output clock polarity

In order to maximize the window where it is safe to capture data we ideally
want to launch data on the opposite edge to which it is captured. Since the
edge on which data is captured depends on the connected device add a
parameter that allows to configure the launching edge.

Signed-off-by: Lars-Peter Clausen <[email protected]>

library/axi_hdmi_tx/axi_hdmi_tx.v

@@ -105,6 +105,8 @@ module axi_hdmi_tx (
   parameter   PCORE_Cr_Cb_N = 0;
   parameter   PCORE_DEVICE_TYPE = 0;
   parameter   PCORE_EMBEDDED_SYNC = 0;
+  /* 0 = Launch on rising edge, 1 = Launch on falling edge */
+  parameter   OUT_CLK_POLARITY = 0;
 
   localparam  XILINX_7SERIES = 0;
   localparam  XILINX_ULTRASCALE = 1;
@@ -376,8 +378,8 @@ module axi_hdmi_tx (
   if (PCORE_DEVICE_TYPE == XILINX_ULTRASCALE) begin
   ODDRE1 #(.SRVAL(1'b0)) i_clk_oddr (
     .SR (1'b0),
-    .D1 (1'b1),
-    .D2 (1'b0),
+    .D1 (~OUT_CLK_POLARITY),
+    .D2 (OUT_CLK_POLARITY),
     .C (hdmi_clk),
     .Q (hdmi_out_clk));
   end
@@ -389,8 +391,8 @@ module axi_hdmi_tx (
     .sset (1'b0),
     .oe (1'b1),
     .outclocken (1'b1),
-    .datain_h (1'b1),
-    .datain_l (1'b0),
+    .datain_h (~OUT_CLK_POLARITY),
+    .datain_l (OUT_CLK_POLARITY),
     .outclock (hdmi_clk),
     .oe_out (),
     .dataout (hdmi_out_clk));
@@ -400,8 +402,8 @@ module axi_hdmi_tx (
     .R (1'b0),
     .S (1'b0),
     .CE (1'b1),
-    .D1 (1'b1),
-    .D2 (1'b0),
+    .D1 (~OUT_CLK_POLARITY),
+    .D2 (OUT_CLK_POLARITY),
     .C (hdmi_clk),
     .Q (hdmi_out_clk));
   end