3 files changed, 30 insertions, 15 deletions

diff --git a/quantum/split_common/matrix.c b/quantum/split_common/matrix.c
index 51bf8b1095..06bab734e7 100644
--- a/quantum/split_common/matrix.c
+++ b/quantum/split_common/matrix.c
@@ -245,48 +245,59 @@ void matrix_init(void) {
     split_post_init();
 }
 
-void matrix_post_scan(void) {
+bool matrix_post_scan(void) {
+    bool changed = false;
     if (is_keyboard_master()) {
         static uint8_t error_count;
 
-        if (!transport_master(matrix + thatHand)) {
+        matrix_row_t slave_matrix[ROWS_PER_HAND] = {0};
+        if (!transport_master(slave_matrix)) {
             error_count++;
 
             if (error_count > ERROR_DISCONNECT_COUNT) {
                 // reset other half if disconnected
                 for (int i = 0; i < ROWS_PER_HAND; ++i) {
-                    matrix[thatHand + i] = 0;
+                    slave_matrix[i] = 0;
                 }
             }
         } else {
             error_count = 0;
         }
 
+        for (int i = 0; i < ROWS_PER_HAND; ++i) {
+            if (matrix[thatHand + i] != slave_matrix[i]) {
+                matrix[thatHand + i] = slave_matrix[i];
+                changed              = true;
+            }
+        }
+
         matrix_scan_quantum();
     } else {
         transport_slave(matrix + thisHand);
 
         matrix_slave_scan_user();
     }
+
+    return changed;
 }
 
 uint8_t matrix_scan(void) {
-    bool changed = false;
+    bool local_changed = false;
 
 #if defined(DIRECT_PINS) || (DIODE_DIRECTION == COL2ROW)
     // Set row, read cols
     for (uint8_t current_row = 0; current_row < ROWS_PER_HAND; current_row++) {
-        changed |= read_cols_on_row(raw_matrix, current_row);
+        local_changed |= read_cols_on_row(raw_matrix, current_row);
     }
 #elif (DIODE_DIRECTION == ROW2COL)
     // Set col, read rows
     for (uint8_t current_col = 0; current_col < MATRIX_COLS; current_col++) {
-        changed |= read_rows_on_col(raw_matrix, current_col);
+        local_changed |= read_rows_on_col(raw_matrix, current_col);
     }
 #endif
 
-    debounce(raw_matrix, matrix + thisHand, ROWS_PER_HAND, changed);
+    debounce(raw_matrix, matrix + thisHand, ROWS_PER_HAND, local_changed);
 
-    matrix_post_scan();
-    return (uint8_t)changed;
+    bool remote_changed = matrix_post_scan();
+    return (uint8_t)(local_changed || remote_changed);
 }
diff --git a/tmk_core/common/keyboard.c b/tmk_core/common/keyboard.c
index a1fbc01da6..aea09169fb 100644
--- a/tmk_core/common/keyboard.c
+++ b/tmk_core/common/keyboard.c
@@ -97,6 +97,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #    include "dip_switch.h"
 #endif
 
+static uint32_t last_matrix_modification_time = 0;
+uint32_t        last_matrix_activity_time(void) { return last_matrix_modification_time; }
+uint32_t        last_matrix_activity_elapsed(void) { return timer_elapsed32(last_matrix_modification_time); }
+
 // Only enable this if console is enabled to print to
 #if defined(DEBUG_MATRIX_SCAN_RATE) && defined(CONSOLE_ENABLE)
 static uint32_t matrix_timer      = 0;
@@ -338,11 +342,8 @@ void keyboard_task(void) {
     housekeeping_task_kb();
     housekeeping_task_user();
 
-#if defined(OLED_DRIVER_ENABLE) && !defined(OLED_DISABLE_TIMEOUT)
-    uint8_t ret = matrix_scan();
-#else
-    matrix_scan();
-#endif
+    uint8_t matrix_changed = matrix_scan();
+    if (matrix_changed) last_matrix_modification_time = timer_read32();
 
     if (should_process_keypress()) {
         for (uint8_t r = 0; r < MATRIX_ROWS; r++) {
@@ -409,7 +410,7 @@ MATRIX_LOOP_END:
     oled_task();
 #    ifndef OLED_DISABLE_TIMEOUT
     // Wake up oled if user is using those fabulous keys!
-    if (ret) oled_on();
+    if (matrix_changed) oled_on();
 #    endif
 #endif
 
diff --git a/tmk_core/common/keyboard.h b/tmk_core/common/keyboard.h
index d04e685cdb..cc5b2e5e42 100644
--- a/tmk_core/common/keyboard.h
+++ b/tmk_core/common/keyboard.h
@@ -73,6 +73,9 @@ void keyboard_post_init_user(void);
 void housekeeping_task_kb(void);
 void housekeeping_task_user(void);
 
+uint32_t last_matrix_activity_time(void);     // Timestamp of the last matrix activity
+uint32_t last_matrix_activity_elapsed(void);  // Number of milliseconds since the last matrix activity
+
 #ifdef __cplusplus
 }
 #endif