Avoid 8-bit timer overflows in debounce algorithms (#12240)

* Add fast_timer_t that is 16-bit or 32-bit based on architecture

A 16-bit timer will overflow sooner but be faster to compare on AVR.

* Avoid 8-bit timer overflows in debounce algorithms

Count down remaining elapsed time instead of trying to do 8-bit timer
comparisons.

Add a "none" implementation that is automatically used if DEBOUNCE is
0 otherwise it will break the _pk/_pr count down.

* Avoid unnecessary polling of the entire matrix in sym_eager_pk

The matrix only needs to be updated when a debounce timer expires.

* Avoid unnecessary polling of the entire matrix in sym_eager_pr

The matrix only needs to be updated when a debounce timer expires.

The use of the "needed_update" variable is trying to do what
"matrix_need_update" was added to fix but didn't work because it only
applied when all keys finished debouncing.

* Fix sym_defer_g timing inconsistency compared to other debounce algorithms

DEBOUNCE=5 should process the key after 5ms, not 6ms

* Add debounce tests

1 files changed, 13 insertions, 13 deletions

diff --git a/quantum/debounce/sym_defer_g.c b/quantum/debounce/sym_defer_g.c
index 3ed9055d2a..fbefd55ede 100644
--- a/quantum/debounce/sym_defer_g.c
+++ b/quantum/debounce/sym_defer_g.c
@@ -1,5 +1,6 @@
 /*
 Copyright 2017 Alex Ong<the.onga@gmail.com>
+Copyright 2021 Simon Arlott
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 2 of the License, or
@@ -23,30 +24,29 @@ When no state changes have occured for DEBOUNCE milliseconds, we push the state.
 #    define DEBOUNCE 5
 #endif
 
-void        debounce_init(uint8_t num_rows) {}
+#if DEBOUNCE > 0
 static bool debouncing = false;
+static fast_timer_t debouncing_time;
 
-#if DEBOUNCE > 0
-static uint16_t debouncing_time;
-void            debounce(matrix_row_t raw[], matrix_row_t cooked[], uint8_t num_rows, bool changed) {
+void debounce_init(uint8_t num_rows) {}
+
+void debounce(matrix_row_t raw[], matrix_row_t cooked[], uint8_t num_rows, bool changed) {
     if (changed) {
         debouncing      = true;
-        debouncing_time = timer_read();
+        debouncing_time = timer_read_fast();
     }
 
-    if (debouncing && timer_elapsed(debouncing_time) > DEBOUNCE) {
+    if (debouncing && timer_elapsed_fast(debouncing_time) >= DEBOUNCE) {
         for (int i = 0; i < num_rows; i++) {
             cooked[i] = raw[i];
         }
         debouncing = false;
     }
 }
-#else  // no debouncing.
-void debounce(matrix_row_t raw[], matrix_row_t cooked[], uint8_t num_rows, bool changed) {
-    for (int i = 0; i < num_rows; i++) {
-        cooked[i] = raw[i];
-    }
-}
-#endif
 
 bool debounce_active(void) { return debouncing; }
+
+void debounce_free(void) {}
+#else  // no debouncing.
+#    include "none.c"
+#endif