Fix oled_render to render all dirty blocks. (#18887)

drivers/oled/ssd1306_sh1106.c

@@ -291,18 +291,18 @@ static void rotate_90(const uint8_t *src, uint8_t *dest) {
 }
 
 void oled_render(void) {
-    if (!oled_initialized) {
-        return;
-    }
-
     // Do we have work to do?
     oled_dirty &= OLED_ALL_BLOCKS_MASK;
-    if (!oled_dirty || oled_scrolling) {
+    if (!oled_dirty || !oled_initialized || oled_scrolling) {
         return;
     }
 
-    // Find first dirty block
+    // Turn on display if it is off
+    oled_on();
+
     uint8_t update_start = 0;
+    while (oled_dirty) { // render all dirty blocks
+        // Find next dirty block
         while (!(oled_dirty & ((OLED_BLOCK_TYPE)1 << update_start))) {
             ++update_start;
         }
@@ -345,11 +345,9 @@ void oled_render(void) {
             }
         }
 
-    // Turn on display if it is off
-    oled_on();
-
-    // Clear dirty flag
+        // Clear dirty flag of just rendered block
         oled_dirty &= ~((OLED_BLOCK_TYPE)1 << update_start);
+    }
 }
 
 void oled_set_cursor(uint8_t col, uint8_t line) {