zephyr: test: Fix flaky keyboard_scan test

Latent key presses were appearing in a subsequent test, throwing off FFF
expectations. Resolved by adding a test-only helper function to
`keyboard_scan.c` to wipe out the debouncing state between tests. Also
broke out the failing test into two independent ones.

BRANCH=None
BUG=None
TEST=./twister -s drivers/drivers.keyboard_scan

Change-Id: I79f2a6891f36e10a7df87865573348312c5b57d5
Signed-off-by: Tristan Honscheid <honscheid@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4404706
Reviewed-by: Al Semjonovs <asemjonovs@google.com>

3 files changed, 49 insertions, 17 deletions

diff --git a/common/keyboard_scan.c b/common/keyboard_scan.c
index e78d130289..1568f5ae10 100644
--- a/common/keyboard_scan.c
+++ b/common/keyboard_scan.c
@@ -1199,4 +1199,15 @@ __test_only void keyboard_scan_set_print_state_changes(int val)
 {
 	print_state_changes = val;
 }
+
+__test_only void test_keyboard_scan_debounce_reset(void)
+{
+	memset(&debouncing, 0, sizeof(debouncing));
+	memset(&debounced_state, 0, sizeof(debounced_state));
+	memset(&scan_time, 0, sizeof(scan_time));
+	memset(&scan_edge_index, 0, sizeof(scan_edge_index));
+
+	scan_time_index = 0;
+	post_scan_clock_us = 0;
+}
 #endif /* TEST_BUILD */
diff --git a/include/keyboard_scan.h b/include/keyboard_scan.h
index 4138f11ca5..544f973946 100644
--- a/include/keyboard_scan.h
+++ b/include/keyboard_scan.h
@@ -185,6 +185,11 @@ __test_only void keyboard_scan_set_print_state_changes(int val);
  * @return int non-zero if enabled, zero otherwise.
  */
 int keyboard_scan_is_enabled(void);
+
+/**
+ * @brief Reset key debouncing logic
+ */
+void test_keyboard_scan_debounce_reset(void);
 #endif /* TEST_BUILD */
 
 #endif /* __CROS_EC_KEYBOARD_SCAN_H */
diff --git a/zephyr/test/drivers/keyboard_scan/src/keyboard_scan.c b/zephyr/test/drivers/keyboard_scan/src/keyboard_scan.c
index 71961c0a86..30b5e4521c 100644
--- a/zephyr/test/drivers/keyboard_scan/src/keyboard_scan.c
+++ b/zephyr/test/drivers/keyboard_scan/src/keyboard_scan.c
@@ -195,22 +195,16 @@ ZTEST(keyboard_scan, console_command_kbpress__invalid)
  */
 FAKE_VOID_FUNC(key_state_changed, int, int, uint8_t);
 
-ZTEST(keyboard_scan, console_command_kbpress__press_and_release)
+ZTEST(keyboard_scan, test_console_command_kbpress__press)
 {
-	/* Pres and release a key */
+	/* Press and release a key */
 	zassert_ok(shell_execute_cmd(get_ec_shell(), "kbpress 1 2"));
 
-	/* Hold a key down */
-	zassert_ok(shell_execute_cmd(get_ec_shell(), "kbpress 3 4 1"));
-
-	/* Release the key */
-	zassert_ok(shell_execute_cmd(get_ec_shell(), "kbpress 3 4 0"));
-
 	/* Pause a bit to allow the key scan task to process. */
-	k_sleep(K_MSEC(200));
+	k_sleep(K_MSEC(500));
 
-	/* Expect four key events */
-	zassert_equal(4, key_state_changed_fake.call_count);
+	/* Expect two key events */
+	zassert_equal(2, key_state_changed_fake.call_count);
 
 	/* Press col=1,row=2 (state==1) */
 	zassert_equal(1, key_state_changed_fake.arg1_history[0]);
@@ -221,16 +215,33 @@ ZTEST(keyboard_scan, console_command_kbpress__press_and_release)
 	zassert_equal(1, key_state_changed_fake.arg1_history[1]);
 	zassert_equal(2, key_state_changed_fake.arg0_history[1]);
 	zassert_false(key_state_changed_fake.arg2_history[1]);
+}
+
+ZTEST(keyboard_scan, test_console_command_kbpress__down_and_up)
+{
+	/* Hold a key down */
+	zassert_ok(shell_execute_cmd(get_ec_shell(), "kbpress 3 4 1"));
+
+	/* Release the key */
+	zassert_ok(shell_execute_cmd(get_ec_shell(), "kbpress 3 4 0"));
+
+	/* Pause a bit to allow the key scan task to process. */
+	k_sleep(K_MSEC(500));
+
+	/* Expect two key events */
+	zassert_equal(2, key_state_changed_fake.call_count,
+		      "Actual call_count=%d",
+		      key_state_changed_fake.call_count);
 
 	/* Press col=3,row=4 (state==1) */
-	zassert_equal(3, key_state_changed_fake.arg1_history[2]);
-	zassert_equal(4, key_state_changed_fake.arg0_history[2]);
-	zassert_true(key_state_changed_fake.arg2_history[2]);
+	zassert_equal(3, key_state_changed_fake.arg1_history[0]);
+	zassert_equal(4, key_state_changed_fake.arg0_history[0]);
+	zassert_true(key_state_changed_fake.arg2_history[0]);
 
 	/* Release col=3,row=4 (state==0) */
-	zassert_equal(3, key_state_changed_fake.arg1_history[3]);
-	zassert_equal(4, key_state_changed_fake.arg0_history[3]);
-	zassert_false(key_state_changed_fake.arg2_history[3]);
+	zassert_equal(3, key_state_changed_fake.arg1_history[1]);
+	zassert_equal(4, key_state_changed_fake.arg0_history[1]);
+	zassert_false(key_state_changed_fake.arg2_history[1]);
 }
 
 ZTEST(keyboard_scan, host_command_simulate_key__locked)
@@ -380,6 +391,11 @@ static void reset_keyboard(void *data)
 	/* Reset KB emulator */
 	clear_emulated_keys();
 
+	/* Clear debouncing state to prevent latent key presses from appearing
+	 * in a later test.
+	 */
+	test_keyboard_scan_debounce_reset();
+
 	/* Reset all mocks. */
 	RESET_FAKE(key_state_changed);
 	RESET_FAKE(system_is_locked);