HAL_ChibiOS: fixed cork/push

[tridge]

ensure that period[] array is not updated until we push
this fixes the stuttering motors on tilt quadplanes, and may fix other issues
this is an alternative to #29518

[andyp1per]

I mean shouldn't this always be the case? Couldn't you just assert on the non-corked case?

[tridge]

there could be special cases where we write non-corked, for something going into 4.6.0 I wouldn't want to rule out non-corked output on some weird vehicle setup
one example would be ReplayGyroFFT
another in toy_mode test code
for 4.7.0 I'd be happy to enforce corked only, starting with SITL

[tpwrules]

So the problem is that the period[] array was read by the dshot_send function and values were sent out before the push? Does the memcpy create any tearing problems?

Should read see the pre-push or post-push value? It wasn't involved in the issue was it?

[andyp1per]

So the problem is that the period[] array was read by the dshot_send function and values were sent out before the push? Does the memcpy create any tearing problems?

Should read see the pre-push or post-push value? It wasn't involved in the issue was it?

Once corked, no updates should be seen until push has been called. so read should see the post-pushed or pre-corked values

[IamPete1]

We could also remove the output here:

ardupilot/libraries/SRV_Channel/SRV_Channel_aux.cpp

Line 351 in 83b2a25

channels[i].output_ch();

So the value is not written to the hal.

[andyp1per]

This incurs about a 0.1% CPU cost @2k and 0.2% @4k

[andyp1per]

Briefly tested on my fast rate quad without issue

[IamPete1]

LGTM.