sayma: support external RTM clocking

artiq/firmware/libboard_artiq/ad9154.rs

@@ -33,10 +33,9 @@ fn read(addr: u16) -> u8 {
     }
 }
 
-pub fn jesd_unreset() {
+pub fn jesd_reset(reset: bool) {
     unsafe {
-        csr::ad9154_crg::ibuf_disable_write(0);
-        csr::ad9154_crg::jreset_write(0);
+        csr::ad9154_crg::jreset_write(if reset { 1 }  else { 0 });
     }
 }
 

artiq/firmware/libboard_artiq/hmc830_7043.rs

@@ -367,6 +367,18 @@ pub mod hmc7043 {
         Ok(())
     }
 
+    pub fn enable_fpga_ibuf() {
+        /*
+         * Never missing an opportunity to be awful, the HMC7043 produces broadband noise
+         * prior to intialization, which can upset the FPGA.
+         * One mitigation technique is to disable the input buffer until the HMC7043 is
+         * slightly better behaved.
+         */
+        unsafe {
+            csr::ad9154_crg::ibuf_disable_write(0);
+        }
+    }
+
     pub fn sysref_offset_dac(dacno: u8, phase_offset: u16) {
         /*  Analog delay resolution: 25ps
          *  Digital delay resolution: 1/2 input clock cycle = 416ps for 1.2GHz
@@ -427,6 +439,7 @@ pub fn init() -> Result<(), &'static str> {
     hmc7043::init();
     hmc7043::test_gpo()?;
     hmc7043::check_phased()?;
+    hmc7043::enable_fpga_ibuf();
 
     Ok(())
 }

artiq/firmware/runtime/main.rs

@@ -111,7 +111,7 @@ fn startup() {
     board_artiq::hmc830_7043::init().expect("cannot initialize HMC830/7043");
     #[cfg(has_ad9154)]
     {
-        board_artiq::ad9154::jesd_unreset();
+        board_artiq::ad9154::jesd_reset(false);
         board_artiq::ad9154::init();
         if let Err(e) = board_artiq::jesd204sync::sysref_auto_rtio_align() {
             error!("failed to align SYSREF at FPGA: {}", e);

artiq/firmware/satman/main.rs

@@ -273,11 +273,6 @@ pub extern fn main() -> i32 {
         csr::drtio_transceiver::stable_clkin_write(1);
     }
 
-    #[cfg(has_ad9154)]
-    {
-        board_artiq::ad9154::jesd_unreset();
-        board_artiq::ad9154::init();
-    }
     #[cfg(has_allaki_atts)]
     board_artiq::hmc542::program_all(8/*=4dB*/);
 
@@ -285,12 +280,34 @@ pub extern fn main() -> i32 {
         while !drtio_link_rx_up() {
             process_errors();
         }
+
         info!("link is up, switching to recovered clock");
         si5324::siphaser::select_recovered_clock(true).expect("failed to switch clocks");
         si5324::siphaser::calibrate_skew(SIPHASER_PHASE).expect("failed to calibrate skew");
+
+        #[cfg(has_ad9154)]
+        {
+            /*
+             * One side of the JESD204 elastic buffer is clocked by the Si5324, the other
+             * by the RTM.
+             * The elastic buffer can operate only when those two clocks are derived from
+             * the same oscillator.
+             * This is the case when either of those conditions is true:
+             * (1) The DRTIO master and the RTM are clocked directly from a common external
+             *     source, *and* the Si5324 has locked to the recovered clock.
+             *     This clocking scheme provides less noise and phase drift at the DACs.
+             * (2) The RTM clock is connected to the Si5324 output.
+             * To handle those cases, we simply keep the JESD204 core in reset unless the
+             * Si5324 is locked to the recovered clock.
+             */
+            board_artiq::ad9154::jesd_reset(false);
+            board_artiq::ad9154::init();
+        }
+
         drtioaux::reset(0);
         drtio_reset(false);
         drtio_reset_phy(false);
+
         while drtio_link_rx_up() {
             process_errors();
             process_aux_packets();
@@ -309,6 +326,10 @@ pub extern fn main() -> i32 {
                 }
             }
         }
+
+        #[cfg(has_ad9154)]
+        board_artiq::ad9154::jesd_reset(true);
+
         drtio_reset_phy(true);
         drtio_reset(true);
         drtio_tsc_loaded();

artiq/gateware/targets/sayma_amc.py

@@ -577,7 +577,7 @@ class Satellite(BaseSoC, RTMCommon):
 
         self.comb += platform.request("sfp_tx_disable", 0).eq(0)
         self.submodules.drtio_transceiver = gth_ultrascale.GTH(
-            clock_pads=self.ad9154_crg.refclk,
+            clock_pads=platform.request("si5324_clkout"),
             data_pads=[platform.request("sfp", 0)],
             sys_clk_freq=self.clk_freq,
             rtio_clk_freq=rtio_clk_freq)
@@ -599,7 +599,7 @@ class Satellite(BaseSoC, RTMCommon):
         self.config["RTIO_FREQUENCY"] = str(rtio_clk_freq/1e6)
         self.submodules.siphaser = SiPhaser7Series(
             si5324_clkin=platform.request("si5324_clkin"),
-            si5324_clkout_fabric=platform.request("adc_sysref"))
+            si5324_clkout_fabric=platform.request("si5324_clkout_fabric"))
         platform.add_platform_command("set_property CLOCK_DEDICATED_ROUTE FALSE [get_nets {mmcm_ps}]",
             mmcm_ps=self.siphaser.mmcm_ps_output)
         platform.add_false_path_constraints(
@@ -612,11 +612,6 @@ class Satellite(BaseSoC, RTMCommon):
         self.csr_devices.append("i2c")
         self.config["I2C_BUS_COUNT"] = 1
         self.config["HAS_SI5324"] = None
-        # ensure pins are properly biased and terminated
-        si5324_clkout = platform.request("si5324_clkout", 0)
-        self.specials += Instance(
-            "IBUFDS_GTE3", i_CEB=0, i_I=si5324_clkout.p, i_IB=si5324_clkout.n,
-            attr={("DONT_TOUCH", "true")})
 
         self.submodules.sysref_sampler = jesd204_tools.SysrefSampler(
             self.drtio0.coarse_ts, self.ad9154_crg.jref)