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firmware: implement DDMTD-based SYSREF/RTIO alignment (draft) 

Mostly works and usually gets the DAC synchronized at 2.4GHz with Urukul across DRTIO.

Needs cleanup and optimization/characterization.
This commit is contained in:
Sebastien Bourdeauducq 2019-01-27 09:51:24 +08:00
parent 8632b553d2
commit f73ffe44f9
1 changed files with 209 additions and 8 deletions
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217
artiq/firmware/libboard_artiq/jesd204sync.rs
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@ -3,6 +3,67 @@ use board_misoc::{csr, clock, config};
use hmc830_7043::hmc7043;
use ad9154;
fn average_2phases(a: i32, b:i32, modulo: i32) -> i32 {
let diff = ((a - b + modulo/2 + modulo) % modulo) - modulo/2;
return (modulo + b + diff/2) % modulo;
}
fn average_phases(phases: &[i32], modulo: i32) -> i32 {
if phases.len() == 1 {
panic!("input array length must be a power of 2");
} else if phases.len() == 2 {
average_2phases(phases[0], phases[1], modulo)
} else {
let cut = phases.len()/2;
average_2phases(
average_phases(&phases[..cut], modulo),
average_phases(&phases[cut..], modulo),
modulo)
}
}
const DDMTD_N_SHIFT: i32 = 6;
const DDMTD_N: i32 = 1 << DDMTD_N_SHIFT;
const SYSREF_SH_PRECISION_SHIFT: i32 = 5;
const SYSREF_SH_PRECISION: i32 = 1 << SYSREF_SH_PRECISION_SHIFT;
const SYSREF_SH_MOD: i32 = 1 << (DDMTD_N_SHIFT + SYSREF_SH_PRECISION_SHIFT);
fn measure_ddmdt_phase_raw() -> i32 {
unsafe { csr::sysref_ddmtd::dt_read() as i32 }
}
fn measure_ddmdt_phase() -> i32 {
let mut measurements = [0; SYSREF_SH_PRECISION as usize];
for i in 0..SYSREF_SH_PRECISION {
measurements[i as usize] = measure_ddmdt_phase_raw() << SYSREF_SH_PRECISION_SHIFT;
clock::spin_us(10);
}
average_phases(&measurements, SYSREF_SH_MOD) >> SYSREF_SH_PRECISION_SHIFT
}
fn test_slip_ddmtd() -> Result<(), &'static str> {
// expected_step = (RTIO clock frequency)*(DDMTD N)/(HMC7043 CLKIN frequency)
let expected_step = 4;
let tolerance = 1;
info!("testing HMC7043 SYSREF slip against DDMTD...");
let mut old_phase = measure_ddmdt_phase();
for _ in 0..1024 {
hmc7043::sysref_slip();
let phase = measure_ddmdt_phase();
let step = (DDMTD_N + old_phase - phase) % DDMTD_N;
if (step - expected_step).abs() > tolerance {
error!(" ...got unexpected step: {}", step);
return Err("HMC7043 SYSREF slip produced unexpected DDMTD step");
}
old_phase = phase;
}
info!(" ...passed");
Ok(())
}
fn sysref_sh_error() -> bool {
unsafe {
csr::sysref_sampler::sh_error_reset_write(1);
@ -13,13 +74,150 @@ fn sysref_sh_error() -> bool {
}
}
pub fn sysref_auto_rtio_align() -> Result<(), &'static str> {
for _ in 0..256 {
#[derive(Default)]
struct SysrefShLimits {
rising_phases: [i32; SYSREF_SH_PRECISION as usize],
falling_phases: [i32; SYSREF_SH_PRECISION as usize],
}
fn measure_sysref_sh_limits() -> Result<SysrefShLimits, &'static str> {
let mut ret = SysrefShLimits::default();
let mut nslips = 0;
let mut rising_n = 0;
let mut falling_n = 0;
let mut previous = sysref_sh_error();
while rising_n < SYSREF_SH_PRECISION || falling_n < SYSREF_SH_PRECISION {
hmc7043::sysref_slip();
let dt = unsafe { csr::sysref_ddmtd::dt_read() };
let sh_error = sysref_sh_error();
info!("dt={} sysref_sh_error={}", dt, sh_error);
nslips += 1;
if nslips > 1024 {
return Err("too many slips and not enough SYSREF S/H error transitions");
}
let current = sysref_sh_error();
let phase = measure_ddmdt_phase();
if current && !previous && rising_n < SYSREF_SH_PRECISION {
ret.rising_phases[rising_n as usize] = phase << SYSREF_SH_PRECISION_SHIFT;
rising_n += 1;
}
if !current && previous && falling_n < SYSREF_SH_PRECISION {
ret.falling_phases[falling_n as usize] = phase << SYSREF_SH_PRECISION_SHIFT;
falling_n += 1;
}
previous = current;
}
Ok(ret)
}
fn max_phase_deviation(average: i32, phases: &[i32]) -> i32 {
let mut ret = 0;
for phase in phases.iter() {
let deviation = (phase - average).abs();
if deviation > ret {
ret = deviation;
}
}
return ret;
}
fn reach_sysref_ddmtd_target(target: i32, tolerance: i32) -> Result<(), &'static str> {
let mut phase = measure_ddmdt_phase();
let mut nslips = 0;
while (phase - target).abs() > tolerance {
hmc7043::sysref_slip();
nslips += 1;
if nslips > 1024 {
return Err("failed to reach SYSREF DDMTD phase target");
}
phase = measure_ddmdt_phase();
}
Ok(())
}
fn calibrate_sysref_target(rising_average: i32, falling_average: i32) -> Result<i32, &'static str> {
let coarse_target = (falling_average - 16 + DDMTD_N) % DDMTD_N; // HACK
info!("SYSREF calibration coarse target: {}", coarse_target);
reach_sysref_ddmtd_target(coarse_target, 2)?;
let target = measure_ddmdt_phase();
info!("SYSREF calibrated target: {}", target);
Ok(target)
}
fn sysref_get_sample() -> Result<bool, &'static str> {
if sysref_sh_error() {
return Err("SYSREF failed S/H timing");
}
let ret = unsafe { csr::sysref_sampler::sample_result_read() } != 0;
Ok(ret)
}
fn sysref_slip_rtio_cycle() {
for _ in 0..hmc7043::FPGA_CLK_DIV {
hmc7043::sysref_slip();
}
}
pub fn sysref_rtio_align() -> Result<(), &'static str> {
let mut previous_sample = sysref_get_sample()?;
let mut nslips = 0;
loop {
sysref_slip_rtio_cycle();
let sample = sysref_get_sample()?;
if sample && !previous_sample {
info!("SYSREF aligned with RTIO TSC");
return Ok(())
}
previous_sample = sample;
nslips += 1;
if nslips > hmc7043::SYSREF_DIV/hmc7043::FPGA_CLK_DIV {
return Err("failed to find SYSREF transition aligned with RTIO TSC");
}
}
}
pub fn sysref_auto_rtio_align() -> Result<(), &'static str> {
test_slip_ddmtd()?;
let sysref_sh_limits = measure_sysref_sh_limits()?;
let rising_average = average_phases(&sysref_sh_limits.rising_phases, SYSREF_SH_MOD);
let falling_average = average_phases(&sysref_sh_limits.falling_phases, SYSREF_SH_MOD);
let rising_max_deviation = max_phase_deviation(rising_average, &sysref_sh_limits.rising_phases);
let falling_max_deviation = max_phase_deviation(falling_average, &sysref_sh_limits.falling_phases);
let rising_average = rising_average >> SYSREF_SH_PRECISION_SHIFT;
let falling_average = falling_average >> SYSREF_SH_PRECISION_SHIFT;
let rising_max_deviation = rising_max_deviation >> SYSREF_SH_PRECISION_SHIFT;
let falling_max_deviation = falling_max_deviation >> SYSREF_SH_PRECISION_SHIFT;
info!("SYSREF S/H average limits (DDMTD phases): {} {}", rising_average, falling_average);
info!("SYSREF S/H maximum limit deviation: {} {}", rising_max_deviation, falling_max_deviation);
if rising_max_deviation > 4 || falling_max_deviation > 4 {
return Err("excessive SYSREF S/H limit deviation");
}
let entry = config::read_str("sysref_ddmtd_phase_fpga", |r| r.map(|s| s.parse()));
let target_phase = match entry {
Ok(Ok(phase)) => {
info!("using FPGA SYSREF DDMTD phase target from config: {}", phase);
phase
}
_ => {
let phase = calibrate_sysref_target(rising_average, falling_average)?;
if let Err(e) = config::write_int("sysref_ddmtd_phase_fpga", phase as u32) {
error!("failed to update FPGA SYSREF DDMTD phase target in config: {}", e);
}
phase
}
};
reach_sysref_ddmtd_target(target_phase, 1)?;
if sysref_sh_error() {
return Err("SYSREF does not meet S/H timing at DDMTD phase target");
}
sysref_rtio_align()?;
Ok(())
}
@ -120,12 +318,15 @@ pub fn sysref_auto_dac_align() -> Result<(), &'static str> {
// We assume that DAC SYSREF traces are length-matched so only one phase
// value is needed, and we use DAC-0 as calibration reference.
let entry = config::read_str("sysref_phase_dac", |r| r.map(|s| s.parse()));
let entry = config::read_str("sysref_7043_phase_dac", |r| r.map(|s| s.parse()));
let phase = match entry {
Ok(Ok(phase)) => phase,
Ok(Ok(phase)) => {
info!("using DAC SYSREF phase from config: {}", phase);
phase
},
_ => {
let phase = sysref_cal_dac(0)?;
if let Err(e) = config::write_int("sysref_phase_dac", phase as u32) {
if let Err(e) = config::write_int("sysref_7043_phase_dac", phase as u32) {
error!("failed to update DAC SYSREF phase in config: {}", e);
}
phase