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sdram: simplify read level scan

This commit is contained in:
Robert Jördens 2018-03-19 18:41:56 +00:00
parent 845784c180
commit 4b3f408143
1 changed files with 35 additions and 35 deletions
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28
artiq/firmware/libboard/sdram.rs
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@ -316,11 +316,14 @@ mod ddr {
for n in 0..DQS_SIGNAL_COUNT {
ddrphy::dly_sel_write(1 << (DQS_SIGNAL_COUNT - n - 1));
let find_edge = |which| {
// Find the first (which=true) or last (which=false) tap that leads to a
// sufficiently high number of correct reads.
let mut last_valid = 0;
let mut min_delay = 0;
let mut have_min_delay = false;
let mut max_delay = 0;
ddrphy::rdly_dq_rst_write(1);
for delay in 0..DDRPHY_MAX_DELAY {
let mut valid = true;
for _ in 0..256 {
@ -340,26 +343,23 @@ mod ddr {
}
if valid {
last_valid = delay;
if which {
break;
if !have_min_delay {
min_delay = delay;
have_min_delay = true;
}
max_delay = delay;
}
ddrphy::rdly_dq_inc_write(1);
}
last_valid
};
// Find smallest working delay
let min_delay = find_edge(true);
let max_delay = find_edge(false);
log!(logger, "{}:{:02}-{:02} ", DQS_SIGNAL_COUNT - n - 1,
min_delay, max_delay);
let mean_delay = (min_delay + max_delay) / 2;
log!(logger, "{}: {} ({} wide), ",
DQS_SIGNAL_COUNT - n - 1, mean_delay,
max_delay - min_delay);
// Set delay to the middle
ddrphy::rdly_dq_rst_write(1);
for _ in 0..(min_delay + max_delay) / 2 {
for _ in 0..mean_delay {
ddrphy::rdly_dq_inc_write(1);
}
}