diff --git a/Marlin/src/HAL/LPC1768/tft/tft_spi.cpp b/Marlin/src/HAL/LPC1768/tft/tft_spi.cpp
index 440e9f8598d5b..2342de002db78 100644
--- a/Marlin/src/HAL/LPC1768/tft/tft_spi.cpp
+++ b/Marlin/src/HAL/LPC1768/tft/tft_spi.cpp
@@ -63,7 +63,7 @@ uint32_t TFT_SPI::getID() {
   return id;
 }
 
-uint32_t TFT_SPI::readID(uint16_t reg) {
+uint32_t TFT_SPI::readID(const uint16_t inReg) {
   uint32_t data = 0;
 
   #if PIN_EXISTS(TFT_MISO)
@@ -72,7 +72,7 @@ uint32_t TFT_SPI::readID(uint16_t reg) {
     SPIx.setClock(SPI_CLOCK_DIV64);
     SPIx.begin();
     WRITE(TFT_CS_PIN, LOW);
-    writeReg(reg);
+    writeReg(inReg);
 
     for (uint8_t i = 0; i < 4; ++i) {
       SPIx.read((uint8_t*)&d, 1);
diff --git a/Marlin/src/HAL/LPC1768/tft/tft_spi.h b/Marlin/src/HAL/LPC1768/tft/tft_spi.h
index 884bcaed04123..0ebb29dd60f28 100644
--- a/Marlin/src/HAL/LPC1768/tft/tft_spi.h
+++ b/Marlin/src/HAL/LPC1768/tft/tft_spi.h
@@ -56,7 +56,7 @@
 
 class TFT_SPI {
 private:
-  static uint32_t readID(uint16_t reg);
+  static uint32_t readID(const uint16_t inReg);
   static void transmit(uint16_t data);
   static void transmit(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
   static void transmitDMA(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
@@ -74,7 +74,7 @@ class TFT_SPI {
   static void dataTransferAbort();
 
   static void writeData(uint16_t data) { transmit(data); }
-  static void writeReg(uint16_t reg) { WRITE(TFT_DC_PIN, LOW); transmit(reg); WRITE(TFT_DC_PIN, HIGH); }
+  static void writeReg(const uint16_t inReg) { WRITE(TFT_DC_PIN, LOW); transmit(inReg); WRITE(TFT_DC_PIN, HIGH); }
 
   static void writeSequence_DMA(uint16_t *data, uint16_t count) { transmitDMA(DMA_MINC_ENABLE, data, count); }
   static void writeMultiple_DMA(uint16_t color, uint16_t count) { static uint16_t data; data = color; transmitDMA(DMA_MINC_DISABLE, &data, count); }
diff --git a/Marlin/src/HAL/NATIVE_SIM/tft/tft_spi.h b/Marlin/src/HAL/NATIVE_SIM/tft/tft_spi.h
index df7b9420994b9..c388f3288bbc8 100644
--- a/Marlin/src/HAL/NATIVE_SIM/tft/tft_spi.h
+++ b/Marlin/src/HAL/NATIVE_SIM/tft/tft_spi.h
@@ -40,7 +40,7 @@
 
 class TFT_SPI {
 private:
-  static uint32_t readID(uint16_t reg);
+  static uint32_t readID(const uint16_t inReg);
   static void transmit(uint16_t data);
   static void transmitDMA(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
 
@@ -57,7 +57,7 @@ class TFT_SPI {
   static void dataTransferAbort();
 
   static void writeData(uint16_t data);
-  static void writeReg(uint16_t reg);
+  static void writeReg(const uint16_t inReg);
 
   static void writeSequence_DMA(uint16_t *data, uint16_t count) { writeSequence(data, count); }
   static void writeMultiple_DMA(uint16_t color, uint16_t count) { writeMultiple(color, count); }
diff --git a/Marlin/src/HAL/STM32/tft/tft_fsmc.cpp b/Marlin/src/HAL/STM32/tft/tft_fsmc.cpp
index 35606460ac628..8e4f97d0a32e7 100644
--- a/Marlin/src/HAL/STM32/tft/tft_fsmc.cpp
+++ b/Marlin/src/HAL/STM32/tft/tft_fsmc.cpp
@@ -135,11 +135,11 @@ uint32_t TFT_FSMC::getID() {
   return id;
 }
 
-uint32_t TFT_FSMC::readID(tft_data_t reg) {
+uint32_t TFT_FSMC::readID(const tft_data_t inReg) {
   uint32_t id;
-  writeReg(reg);
+  writeReg(inReg);
   id = LCD->RAM; // dummy read
-  id = reg << 24;
+  id = inReg << 24;
   id |= (LCD->RAM & 0x00FF) << 16;
   id |= (LCD->RAM & 0x00FF) << 8;
   id |= LCD->RAM & 0x00FF;
diff --git a/Marlin/src/HAL/STM32/tft/tft_fsmc.h b/Marlin/src/HAL/STM32/tft/tft_fsmc.h
index 1b0a45ff79ac5..e710e5511cf42 100644
--- a/Marlin/src/HAL/STM32/tft/tft_fsmc.h
+++ b/Marlin/src/HAL/STM32/tft/tft_fsmc.h
@@ -62,7 +62,7 @@ class TFT_FSMC {
 
     static LCD_CONTROLLER_TypeDef *LCD;
 
-    static uint32_t readID(tft_data_t reg);
+    static uint32_t readID(const tft_data_t reg);
     static void transmit(tft_data_t data) { LCD->RAM = data; __DSB(); }
     static void transmit(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
     static void transmitDMA(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
@@ -77,7 +77,7 @@ class TFT_FSMC {
     static void dataTransferEnd() {}
 
     static void writeData(uint16_t data) { transmit(tft_data_t(data)); }
-    static void writeReg(uint16_t reg) { LCD->REG = tft_data_t(reg); __DSB(); }
+    static void writeReg(const uint16_t inReg) { LCD->REG = tft_data_t(inReg); __DSB(); }
 
     static void writeSequence_DMA(uint16_t *data, uint16_t count) { transmitDMA(DMA_PINC_ENABLE, data, count); }
     static void writeMultiple_DMA(uint16_t color, uint16_t count) { static uint16_t data; data = color; transmitDMA(DMA_PINC_DISABLE, &data, count); }
diff --git a/Marlin/src/HAL/STM32/tft/tft_ltdc.cpp b/Marlin/src/HAL/STM32/tft/tft_ltdc.cpp
index ce47d2e1ecdfa..3bbc39f20a8fc 100644
--- a/Marlin/src/HAL/STM32/tft/tft_ltdc.cpp
+++ b/Marlin/src/HAL/STM32/tft/tft_ltdc.cpp
@@ -267,7 +267,7 @@ uint32_t TFT_LTDC::getID() {
   return 0xABAB;
 }
 
-uint32_t TFT_LTDC::readID(tft_data_t reg) {
+uint32_t TFT_LTDC::readID(const tft_data_t inReg) {
   return 0xABAB;
 }
 
@@ -352,10 +352,6 @@ void TFT_LTDC::transmit(tft_data_t data) {
   }
 }
 
-void TFT_LTDC::writeReg(uint16_t reg) {
-  reg = reg;
-}
-
 void TFT_LTDC::transmit(uint32_t memoryIncrease, uint16_t *data, uint16_t count) {
 
   while (x_cur != x_min && count) {
diff --git a/Marlin/src/HAL/STM32/tft/tft_ltdc.h b/Marlin/src/HAL/STM32/tft/tft_ltdc.h
index d4a254ba7063b..22c3a13778fc7 100644
--- a/Marlin/src/HAL/STM32/tft/tft_ltdc.h
+++ b/Marlin/src/HAL/STM32/tft/tft_ltdc.h
@@ -43,7 +43,7 @@ class TFT_LTDC {
     static uint16_t x_min, x_max, y_min, y_max, x_cur, y_cur;
     static uint8_t reg;
 
-    static uint32_t readID(tft_data_t reg);
+    static uint32_t readID(const tft_data_t inReg);
 
     static uint16_t readPoint(uint16_t x, uint16_t y);
     static void drawPoint(uint16_t x, uint16_t y, uint16_t color);
@@ -62,7 +62,7 @@ class TFT_LTDC {
     static void dataTransferEnd() {};
 
     static void writeData(uint16_t data);
-    static void writeReg(uint16_t reg);
+    static void writeReg(const uint16_t inReg) { reg = inReg; }
 
     // Non-blocking DMA data transfer is not implemented for LTDC interface
     inline static void writeSequence_DMA(uint16_t *data, uint16_t count) { writeSequence(data, count); }
diff --git a/Marlin/src/HAL/STM32/tft/tft_spi.cpp b/Marlin/src/HAL/STM32/tft/tft_spi.cpp
index eebf366b8c38d..eb81a27bf102d 100644
--- a/Marlin/src/HAL/STM32/tft/tft_spi.cpp
+++ b/Marlin/src/HAL/STM32/tft/tft_spi.cpp
@@ -145,7 +145,7 @@ uint32_t TFT_SPI::getID() {
   return id;
 }
 
-uint32_t TFT_SPI::readID(uint16_t reg) {
+uint32_t TFT_SPI::readID(const uint16_t inReg) {
   uint32_t data = 0;
   #if PIN_EXISTS(TFT_MISO)
     uint32_t BaudRatePrescaler = SPIx.Init.BaudRatePrescaler;
@@ -153,7 +153,7 @@ uint32_t TFT_SPI::readID(uint16_t reg) {
 
     SPIx.Init.BaudRatePrescaler = SPIx.Instance == SPI1 ? SPI_BAUDRATEPRESCALER_8 : SPI_BAUDRATEPRESCALER_4;
     dataTransferBegin(DATASIZE_8BIT);
-    writeReg(reg);
+    writeReg(inReg);
 
     if (SPIx.Init.Direction == SPI_DIRECTION_1LINE) SPI_1LINE_RX(&SPIx);
     __HAL_SPI_ENABLE(&SPIx);
diff --git a/Marlin/src/HAL/STM32/tft/tft_spi.h b/Marlin/src/HAL/STM32/tft/tft_spi.h
index 09f0e0810731a..0535113b16854 100644
--- a/Marlin/src/HAL/STM32/tft/tft_spi.h
+++ b/Marlin/src/HAL/STM32/tft/tft_spi.h
@@ -46,7 +46,7 @@ class TFT_SPI {
   static SPI_HandleTypeDef SPIx;
   static DMA_HandleTypeDef DMAtx;
 
-  static uint32_t readID(uint16_t reg);
+  static uint32_t readID(const uint16_t inReg);
   static void transmit(uint16_t data);
   static void transmit(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
   static void transmitDMA(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
@@ -65,7 +65,7 @@ class TFT_SPI {
   static void dataTransferAbort();
 
   static void writeData(uint16_t data) { transmit(data); }
-  static void writeReg(uint16_t reg) { WRITE(TFT_A0_PIN, LOW); transmit(reg); WRITE(TFT_A0_PIN, HIGH); }
+  static void writeReg(const uint16_t inReg) { WRITE(TFT_A0_PIN, LOW); transmit(inReg); WRITE(TFT_A0_PIN, HIGH); }
 
   static void writeSequence_DMA(uint16_t *data, uint16_t count) { transmitDMA(DMA_MINC_ENABLE, data, count); }
   static void writeMultiple_DMA(uint16_t color, uint16_t count) { static uint16_t data; data = color; transmitDMA(DMA_MINC_DISABLE, &data, count); }
diff --git a/Marlin/src/HAL/STM32F1/tft/tft_fsmc.cpp b/Marlin/src/HAL/STM32F1/tft/tft_fsmc.cpp
index a910cd5af080b..51f70b9365276 100644
--- a/Marlin/src/HAL/STM32F1/tft/tft_fsmc.cpp
+++ b/Marlin/src/HAL/STM32F1/tft/tft_fsmc.cpp
@@ -186,8 +186,8 @@ void TFT_FSMC::transmit(uint16_t data) {
   __DSB();
 }
 
-void TFT_FSMC::writeReg(uint16_t reg) {
-  LCD->REG = reg;
+void TFT_FSMC::writeReg(const uint16_t inReg) {
+  LCD->REG = inReg;
   __DSB();
 }
 
@@ -205,11 +205,11 @@ uint32_t TFT_FSMC::getID() {
   return id;
 }
 
- uint32_t TFT_FSMC::readID(uint16_t reg) {
+ uint32_t TFT_FSMC::readID(const uint16_t inReg) {
    uint32_t id;
-   writeReg(reg);
+   writeReg(inReg);
    id = LCD->RAM; // dummy read
-   id = reg << 24;
+   id = inReg << 24;
    id |= (LCD->RAM & 0x00FF) << 16;
    id |= (LCD->RAM & 0x00FF) << 8;
    id |= LCD->RAM & 0x00FF;
diff --git a/Marlin/src/HAL/STM32F1/tft/tft_fsmc.h b/Marlin/src/HAL/STM32F1/tft/tft_fsmc.h
index 0e74ce2c2bd66..67a2b9cd53c11 100644
--- a/Marlin/src/HAL/STM32F1/tft/tft_fsmc.h
+++ b/Marlin/src/HAL/STM32F1/tft/tft_fsmc.h
@@ -54,7 +54,7 @@ class TFT_FSMC {
   private:
     static LCD_CONTROLLER_TypeDef *LCD;
 
-    static uint32_t readID(uint16_t reg);
+    static uint32_t readID(const uint16_t inReg);
     static void transmit(uint16_t data);
     static void transmit(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
     static void transmitDMA(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
@@ -69,7 +69,7 @@ class TFT_FSMC {
     static void dataTransferEnd() {};
 
     static void writeData(uint16_t data) { transmit(data); }
-    static void writeReg(uint16_t reg);
+    static void writeReg(const uint16_t inReg);
 
     static void writeSequence_DMA(uint16_t *data, uint16_t count) { transmitDMA(DMA_PINC_ENABLE, data, count); }
     static void writeMultiple_DMA(uint16_t color, uint16_t count) { static uint16_t data; data = color; transmitDMA(DMA_PINC_DISABLE, &data, count); }
diff --git a/Marlin/src/HAL/STM32F1/tft/tft_spi.cpp b/Marlin/src/HAL/STM32F1/tft/tft_spi.cpp
index 18d5644437614..f26103b25d8df 100644
--- a/Marlin/src/HAL/STM32F1/tft/tft_spi.cpp
+++ b/Marlin/src/HAL/STM32F1/tft/tft_spi.cpp
@@ -93,13 +93,13 @@ uint32_t TFT_SPI::getID() {
   return id;
 }
 
-uint32_t TFT_SPI::readID(uint16_t reg) {
+uint32_t TFT_SPI::readID(const uint16_t inReg) {
   uint32_t data = 0;
 
   #if PIN_EXISTS(TFT_MISO)
     SPIx.setClockDivider(SPI_CLOCK_DIV16);
     dataTransferBegin(DATASIZE_8BIT);
-    writeReg(reg);
+    writeReg(inReg);
 
     for (uint8_t i = 0; i < 4; ++i) {
       uint8_t d;
diff --git a/Marlin/src/HAL/STM32F1/tft/tft_spi.h b/Marlin/src/HAL/STM32F1/tft/tft_spi.h
index d0c2e50486f0d..5a57081c2abd1 100644
--- a/Marlin/src/HAL/STM32F1/tft/tft_spi.h
+++ b/Marlin/src/HAL/STM32F1/tft/tft_spi.h
@@ -63,7 +63,7 @@
 
 class TFT_SPI {
 private:
-  static uint32_t readID(uint16_t reg);
+  static uint32_t readID(const uint16_t inReg);
   static void transmit(uint16_t data);
   static void transmit(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
   static void transmitDMA(uint32_t memoryIncrease, uint16_t *data, uint16_t count);
@@ -81,7 +81,7 @@ class TFT_SPI {
   static void dataTransferAbort();
 
   static void writeData(uint16_t data) { transmit(data); }
-  static void writeReg(uint16_t reg) { WRITE(TFT_DC_PIN, LOW); transmit(reg); WRITE(TFT_DC_PIN, HIGH); }
+  static void writeReg(const uint16_t inReg) { WRITE(TFT_DC_PIN, LOW); transmit(inReg); WRITE(TFT_DC_PIN, HIGH); }
 
   static void writeSequence_DMA(uint16_t *data, uint16_t count) { transmitDMA(DMA_MINC_ENABLE, data, count); }
   static void writeMultiple_DMA(uint16_t color, uint16_t count) { static uint16_t data; data = color; transmitDMA(DMA_MINC_DISABLE, &data, count); }
diff --git a/Marlin/src/lcd/dogm/u8g_dev_tft_upscale_from_128x64.cpp b/Marlin/src/lcd/dogm/u8g_dev_tft_upscale_from_128x64.cpp
index d16693cee4ee6..160ee44122082 100644
--- a/Marlin/src/lcd/dogm/u8g_dev_tft_upscale_from_128x64.cpp
+++ b/Marlin/src/lcd/dogm/u8g_dev_tft_upscale_from_128x64.cpp
@@ -136,8 +136,8 @@ TFT_IO tftio;
   #define TFT_BTOKMENU_COLOR COLOR_RED
 #endif
 
-static void setWindow(u8g_t *u8g, u8g_dev_t *dev, uint16_t Xmin, uint16_t Ymin, uint16_t Xmax, uint16_t Ymax) {
-  tftio.set_window(Xmin, Ymin, Xmax, Ymax);
+static void setWindow(u8g_t *u8g, u8g_dev_t *dev, uint16_t xMin, uint16_t yMin, uint16_t xMax, uint16_t yMax) {
+  tftio.set_window(xMin, yMin, xMax, yMax);
 }
 
 #if HAS_TOUCH_BUTTONS
diff --git a/Marlin/src/lcd/tft/tft.h b/Marlin/src/lcd/tft/tft.h
index 4a1d1d83044e7..15464cb0459d6 100644
--- a/Marlin/src/lcd/tft/tft.h
+++ b/Marlin/src/lcd/tft/tft.h
@@ -72,7 +72,7 @@ class TFT {
     static void abort() { io.abort(); }
     static void write_multiple(uint16_t data, uint16_t count) { io.WriteMultipleDMA(data, count); }
     static void write_sequence(uint16_t *data, uint16_t count) { io.writeSequenceDMA(data, count); }
-    static void set_window(uint16_t Xmin, uint16_t Ymin, uint16_t Xmax, uint16_t Ymax) { io.set_window(Xmin, Ymin, Xmax, Ymax); }
+    static void set_window(uint16_t xMin, uint16_t yMin, uint16_t xMax, uint16_t yMax) { io.set_window(xMin, yMin, xMax, yMax); }
 
     static void fill(uint16_t x, uint16_t y, uint16_t width, uint16_t height, uint16_t color) { queue.fill(x, y, width, height, color); }
     static void canvas(uint16_t x, uint16_t y, uint16_t width, uint16_t height) { queue.canvas(x, y, width, height); }
diff --git a/Marlin/src/lcd/tft_io/tft_io.h b/Marlin/src/lcd/tft_io/tft_io.h
index cbe554436e961..b0d942120239a 100644
--- a/Marlin/src/lcd/tft_io/tft_io.h
+++ b/Marlin/src/lcd/tft_io/tft_io.h
@@ -64,7 +64,7 @@ class TFT_IO {
   inline static void dataTransferEnd() { io.dataTransferEnd(); }
 
   inline static void writeData(uint16_t data) { io.writeData(data); }
-  inline static void writeReg(uint16_t reg) { io.writeReg(reg); }
+  inline static void writeReg(const uint16_t inReg) { io.writeReg(inReg); }
 
   // Blocking IO used by TFT_CLASSIC_UI and TFT_LVGL_UI
   // These functions start data transfer and WAIT for data transfer completion