grabber: add frequency counter

Cameras are a bit obscure about what they output, this can help with troubleshooting.

artiq/firmware/libboard_artiq/grabber.rs

@@ -76,6 +76,13 @@ fn get_last_pixels(g: usize) -> (u16, u16) {
               (csr::GRABBER[g].last_y_read)()) }
 }
 
+fn get_video_clock(g: usize) -> u32 {
+    let freq_count = unsafe {
+        (csr::GRABBER[g].freq_count_read)()
+    } as u32;
+    2*freq_count*(csr::CONFIG_CLOCK_FREQUENCY/1000000)/255
+}
+
 pub fn tick() {
     for g in 0..csr::GRABBER.len() {
         if unsafe { GRABBER_STATE[g] != State::Down } {
@@ -86,8 +93,9 @@ pub fn tick() {
             }
             if unsafe { GRABBER_STATE[g] == State::WaitResolution } {
                 let (last_x, last_y) = get_last_pixels(g);
-                info!("grabber{} detected frame size: {}x{}",
+                info!("grabber{} frame size: {}x{}",
                     g, last_x + 1, last_y + 1);
+                info!("grabber{} video clock: {}MHz", g, get_video_clock(g));
                 unsafe { GRABBER_STATE[g] = State::Up; }
             }
         } else {

artiq/gateware/grabber/core.py

@@ -3,6 +3,34 @@ from migen.genlib.cdc import MultiReg
 from misoc.interconnect.csr import *
 
 
+class FrequencyCounter(Module, AutoCSR):
+    def __init__(self, width=8):
+        self.freq_count = CSRStatus(width)
+
+        # # #
+
+        toggle = Signal(reset_less=True)
+        toggle_sys = Signal()
+        toggle.attr.add("no_retiming")
+        self.sync.cl += toggle.eq(~toggle)
+        self.specials += MultiReg(toggle, toggle_sys)
+
+        timer = Signal(width+1)
+        tick = Signal(reset=1)
+        count = Signal(width)
+        toggle_sys_r = Signal()
+        self.sync += [
+            Cat(timer, tick).eq(timer + 1),
+            toggle_sys_r.eq(toggle_sys),
+            If(tick,
+                self.freq_count.status.eq(count),
+                count.eq(0)
+            ).Else(
+                If(toggle_sys & ~toggle_sys_r, count.eq(count + 1))
+            )
+        ]
+
+
 bitseq = [
     #  0   1   2   3   4   5   6
        6,  5,  4,  3,  2,  1, 27,

artiq/gateware/rtio/phy/grabber.py

@@ -12,8 +12,12 @@ class Grabber(Module):
                                           rtlink.IInterface(10))
 
         self.submodules.deserializer = deserializer_7series.Deserializer(pins)
+        self.submodules.frequency_counter = FrequencyCounter()
         self.submodules.parser = Parser()
         self.comb += self.parser.cl.eq(self.deserializer.q)
 
     def get_csrs(self):
-        return self.deserializer.get_csrs() + self.parser.get_csrs()
+        return (
+            self.deserializer.get_csrs() +
+            self.frequency_counter.get_csrs() +
+            self.parser.get_csrs())