frameline GW: fix gearbox on 10bits

src/gateware/cxp_frame_pipeline.py

@@ -401,7 +401,7 @@ class Frame_Header_Decoder(Module):
 
 class Custom_Pixel_Gearbox(Module):
     def __init__(self, size):
-        assert size in [8, 16]
+        assert size in [8, 10, 16]
 
         self.x_size = Signal(3*char_width)
 
@@ -421,19 +421,19 @@ class Custom_Pixel_Gearbox(Module):
         # Control interface
 
         reset_reg = Signal()
-        level = Signal(max=shift_reg_size)
         we = Signal()
         re = Signal()
+        self.level = Signal(max=shift_reg_size)
         self.w_cnt = Signal(max=shift_reg_size//sink_dw)
         self.r_cnt = Signal(max=shift_reg_size//source_dw)
 
         self.sync += [
             If(reset_reg,
-                level.eq(level.reset),
+                self.level.eq(self.level.reset),
             ).Else(
-                If(we & ~re, level.eq(level + sink_dw)),
+                If(we & ~re, self.level.eq(self.level + sink_dw)),
-                If(~we & re, level.eq(level - source_dw)),
+                If(~we & re, self.level.eq(self.level - source_dw)),
-                If(we & re, level.eq(level + sink_dw - source_dw)),
+                If(we & re, self.level.eq(self.level + sink_dw - source_dw)),
             ),
 
             If(reset_reg,
@@ -457,27 +457,80 @@ class Custom_Pixel_Gearbox(Module):
             )
         ]
          
+        # FIXME: handle linebreak properly for all bits
+        # 1) the COPY may or may not stb data out
+        # 2) the NEWLINE may stb too much
+        # FIXME: the fsm need to be intellgent enough to know whether it need to stb twice or once at eop
+        # need a better generic solution
+        # FIXME: handle last line when the word also are aligned to 4x pixel
         
-        self.submodules.fsm = fsm = FSM(reset_state="COPY")
+        # FACT:
+        # - self.level is only useful for normal ops (i.e. non-linebreak)
+        #   - it should not be used for last pixels
+        # - extra_stb should be reserved for non aligned data only
+        # - after last word, fsm may need to stb 0-2 times
+        #   - which are determined by x_size (varies) & pix size (constant)
+        # - self.valid should be used instead of extra stb when aligned
+         
+        extra_stb = Signal()
+        match size: 
+            case 8 | 16:
+                # no need for extra stb as they are aligned to word boundary no matter what
+                pass
+            case 10:
+                stb_cases = {
+                  5: extra_stb.eq(1),
+                  6: extra_stb.eq(1),
+                  9: extra_stb.eq(1),
+                }
+                # mod 16
+                self.sync += Case(self.x_size[:4], stb_cases)
+            # case 12:
+            #     stb_cases = {
+            #       5: extra_stb.eq(1),
+            #     }
+            #     # mod 8
+            #     self.sync += Case(self.x_size[:3], stb_cases)
+
+
+        # NOTE: 
+        # access to levels -> know when 4x pixels are
+        # access to x_size -> know which pixel at last stb are valid
+        # access to eop -> know when end of line ares
+
+        self.submodules.fsm = fsm = FSM(reset_state="COPY_ALIGNED")
 
         fsm.act(
-            "COPY",
+            "COPY_ALIGNED",
             self.sink.ack.eq(1),
-            self.source.stb.eq(level >= source_dw),
+            self.source.stb.eq(self.level >= source_dw),
             we.eq(self.sink.stb),
             re.eq((self.source.stb & self.source.ack)),
             If(self.sink.stb & self.sink.eop,
-                NextState("NEWLINE"),
+                If(extra_stb,
+                    NextState("EXTRA_STB"),
+                ).Else(
+                    NextState("NEWLINE"),
+                )
             ),
         )
 
+        fsm.act(
+            "EXTRA_STB",
+            self.source.stb.eq(self.level >= source_dw),
+            re.eq((self.source.stb & self.source.ack)),
+            NextState("NEWLINE"),
+        )
+
+        # determine to stb 1 or 2 times
+        # only the last stb will use valid_stb
         valid_stb = Signal()
         fsm.act(
             "NEWLINE",
+            self.source.stb.eq(1),
             reset_reg.eq(1),
             valid_stb.eq(1),
-            self.source.stb.eq(1),
+            NextState("COPY_ALIGNED"),
-            NextState("COPY"),
         )
 
         # Data path
@@ -533,7 +586,10 @@ class Frame_Deserializer(Module):
         self.sync += eol_inserter.l_size.eq(self.l_size),
 
 
-        self.submodules.gearbox = gearbox = Custom_Pixel_Gearbox(16)
+        # TODO: fix the edge case where 5 x_size is not working
+        # the issue arises when the 4th pixel is sent with eop (e.g. 10bits & x_size = 5,6)
+        # eating the rest of the bits
+        self.submodules.gearbox = gearbox = Custom_Pixel_Gearbox(12)
         self.sync += gearbox.x_size.eq(self.x_size),
 
         self.comb += eol_inserter.source.connect(gearbox.sink)