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HAL_ChibiOS: prevent long timeouts in DShot 

this prevents bad calculated timeouts in DShot. The timeout would
sometimes come out as 0xFFFFFFFF, which led to an assert and could
block the thread

This fix is meant to be minimilistic to allow it to be merged easily
into 4.2. A better fix would fix all the uint32_t wrap handling in
DShot
This commit is contained in:
Andrew Tridgell 2022-04-02 19:05:30 +11:00
parent 061b0580b3
commit 8055ba9837
1 changed files with 13 additions and 4 deletions
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17
libraries/AP_HAL_ChibiOS/RCOutput.cpp
View File

@ -237,14 +237,23 @@ void RCOutput::dshot_collect_dma_locks(uint32_t time_out_us)
// if we have time left wait for the event // if we have time left wait for the event
eventmask_t mask = 0; eventmask_t mask = 0;
const uint32_t pulse_elapsed_us = now - group.last_dmar_send_us; const uint32_t pulse_elapsed_us = now - group.last_dmar_send_us;
uint32_t wait_us = 0;
if (now < time_out_us) { if (now < time_out_us) {
mask = chEvtWaitOneTimeout(group.dshot_event_mask, wait_us = MAX(time_out_us - now, group.dshot_pulse_send_time_us - pulse_elapsed_us);
chTimeUS2I(MAX(time_out_us - now, group.dshot_pulse_send_time_us - pulse_elapsed_us)));
} else if (pulse_elapsed_us < group.dshot_pulse_send_time_us) { } else if (pulse_elapsed_us < group.dshot_pulse_send_time_us) {
// better to let the burst write in progress complete rather than cancelling mid way through // better to let the burst write in progress complete rather than cancelling mid way through
mask = chEvtWaitOneTimeout(group.dshot_event_mask, wait_us = group.dshot_pulse_send_time_us - pulse_elapsed_us;
chTimeUS2I(group.dshot_pulse_send_time_us - pulse_elapsed_us));
} }
// waiting for a very short period of time can cause a
// timer wrap with ChibiOS timers. Use CH_CFG_ST_TIMEDELTA
// as minimum. Don't allow for a very long delay (over 1200us)
// to prevent bugs in handling timer wrap
const uint32_t max_delay_us = 1200;
const uint32_t min_delay_us = 10; // matches our CH_CFG_ST_TIMEDELTA
wait_us = constrain_uint32(wait_us, min_delay_us, max_delay_us);
mask = chEvtWaitOneTimeout(group.dshot_event_mask, chTimeUS2I(wait_us));
// no time left cancel and restart // no time left cancel and restart
if (!mask) { if (!mask) {
dma_cancel(group); dma_cancel(group);