soc/cores/pwm: Add MultiChannelPWM core reusing PWM module.

Also do minor changes to PWM module to allow reuse.

litex/soc/cores/pwm.py

@@ -19,7 +19,7 @@ class PWM(Module, AutoCSR):
     Pulse Width Modulation can be useful for various purposes: dim leds, regulate a fan, control
     an oscillator. Software can configure the PWM width and period and enable/disable it.
     """
-    def __init__(self, pwm=None, clock_domain="sys", with_csr=True,
+    def __init__(self, pwm=None, clock_domain="sys", counter=None, with_csr=True,
         default_enable = 0,
         default_width  = 0,
         default_period = 0):
@@ -32,30 +32,34 @@ class PWM(Module, AutoCSR):
 
         # # #
 
-        counter = Signal(32, reset_less=True)
-
         sync = getattr(self.sync, clock_domain)
+
+        # PWM Counter/Period logic.
+        if counter is None:
+            self.counter = counter = Signal(32, reset_less=True)
+            sync += [
+                counter.eq(0),
+                If(self.enable & ~self.reset,
+                    If(counter < (self.period - 1),
+                        counter.eq(counter + 1)
+                    )
+                )
+            ]
+
+        # PWM Width logic.
         sync += [
+            pwm.eq(0),
             If(self.enable & ~self.reset,
-                counter.eq(counter + 1),
                 If(counter < self.width,
                     pwm.eq(1)
-                ).Else(
-                    pwm.eq(0)
-                ),
-                If(counter >= (self.period - 1),
-                    counter.eq(0)
                 )
-            ).Else(
-                counter.eq(0),
-                pwm.eq(0)
             )
         ]
 
         if with_csr:
             self.add_csr(clock_domain)
 
-    def add_csr(self, clock_domain):
+    def add_enable_width_csr(self, clock_domain):
         self._enable = CSRStorage(description="""PWM Enable.\n
             Write ``1`` to enable PWM.""",
             reset = self.enable.reset)
@@ -63,13 +67,55 @@ class PWM(Module, AutoCSR):
             Defines the *Duty cycle* of the PWM. PWM is active high for *Width* ``{cd}_clk`` cycles and
             active low for *Period - Width* ``{cd}_clk`` cycles.""".format(cd=clock_domain),
             reset = self.width.reset)
-        self._period = CSRStorage(32, reset_less=True, description="""PWM Period.\n
-            Defines the *Period* of the PWM in ``{cd}_clk`` cycles.""".format(cd=clock_domain),
-            reset = self.period.reset)
 
         n = 0 if clock_domain == "sys" else 2
         self.specials += [
             MultiReg(self._enable.storage, self.enable, n=n),
             MultiReg(self._width.storage,  self.width,  n=n),
-            MultiReg(self._period.storage, self.period, n=n),
         ]
+
+    def add_period_csr(self, clock_domain):
+        self._period = CSRStorage(32, reset_less=True, description="""PWM Period.\n
+            Defines the *Period* of the PWM in ``{cd}_clk`` cycles.""".format(cd=clock_domain),
+            reset = self.period.reset)
+
+        n = 0 if clock_domain == "sys" else 2
+        self.specials += MultiReg(self._period.storage, self.period, n=n)
+
+    def add_csr(self, clock_domain):
+        self.add_enable_width_csr(clock_domain)
+        self.add_period_csr(clock_domain)
+
+# Multi Channel Pulse Width Modulation -------------------------------------------------------------
+
+class MultiChannelPWM(Module, AutoCSR):
+    """Multi-Channel Pulse Width Modulation
+
+    PWM module with Multi-Channel support.
+    """
+    def __init__(self, pads, clock_domain="sys",
+        default_enable = 0,
+        default_width  = 0,
+        default_period = 0):
+
+        # # #
+
+        nchannels = len(pads)
+
+        counter = Signal(32, reset_less=True)
+        for n in range(nchannels):
+            pwm = PWM(
+                pwm            = pads[n],
+                clock_domain   = clock_domain,
+                with_csr       = False,
+                counter        = None if n == 0 else counter,
+                default_enable = default_enable,
+                default_width  = default_width,
+                default_period = default_period,
+            )
+
+            if n == 0:
+                self.comb += counter.eq(pwm.counter)
+                pwm.add_period_csr(clock_domain)
+            pwm.add_enable_width_csr(clock_domain)
+            self.add_module(name=f"channel{n}", module=pwm)