Add an increment to tcc_refcount to allow deinit to work correctly

[DavePutz]

Issue#2894. When adding to a previously allocated tcc channel the tcc_refcount was not being incremented. This led to a deinit of the PWMOut not releasing properly, and so eventually running out of timers.

[tannewt]

Thanks for looking into this @DavePutz ! Could further explain the cause of this? If we didn't increment enough, I'd expect it to release too early but not cause us to run out of timers. Thanks!

[DavePutz]

Hi Scott, The issue is that in common_hal_pulseio_pwmout_deinit() we have: ```c tcc_refcount[t->index]--; tcc_channels[t->index] &= ~(1 << tcc_channel(t)); if (tcc_refcount[t->index] == 0) { ``` What I saw in a debugger was that refcount was going to 255; i.e. being decremented even though it was already at 0 (due to not being incremented properly). Since it was not then == 0, the code in the if statement would not be run, and the timer not properly released. Hope this helps, -Dave

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On Thu, May 21, 2020 at 12:21 PM Scott Shawcroft ***@***.***> wrote: Thanks for looking into this @DavePutz <https://github.com/DavePutz> ! Could further explain the cause of this? If we didn't increment enough, I'd expect it to release too early but not cause us to run out of timers. Thanks! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#2938 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFNJKEU5LCEVYLBI5436GQTRSVPIXANCNFSM4NG6ZMEQ> .

[tannewt]

Ah! Ok. Thanks!