From 5ff098d2fbe85681de996708950db60ea8b4e6d6 Mon Sep 17 00:00:00 2001
From: Silvano Seva <silseva@fastwebnet.it>
Date: Wed, 17 Jan 2024 01:24:20 +0100
Subject: [PATCH] Removed framebuffer from MDx display driver

---
 platform/drivers/display/HX8353_MD3x.cpp    | 21 ++++-----------------
 platform/mcu/STM32F4xx/linker_script_MDx.ld | 18 +++++++++---------
 2 files changed, 13 insertions(+), 26 deletions(-)

diff --git a/platform/drivers/display/HX8353_MD3x.cpp b/platform/drivers/display/HX8353_MD3x.cpp
index fc609574..949858a7 100644
--- a/platform/drivers/display/HX8353_MD3x.cpp
+++ b/platform/drivers/display/HX8353_MD3x.cpp
@@ -87,12 +87,6 @@
 #define LCD_FSMC_ADDR_COMMAND 0x60000000
 #define LCD_FSMC_ADDR_DATA    0x60040000
 
-/*
- * LCD framebuffer, statically allocated and placed in the "large" RAM block
- * starting at 0x20000000 and accessible by the DMA.
- * Pixel format is RGB565, 16 bit per pixel.
- */
-static uint16_t __attribute__((section(".bss2"))) frameBuffer[CONFIG_SCREEN_WIDTH * CONFIG_SCREEN_HEIGHT];
 
 using namespace miosix;
 static Thread *lcdWaiting = 0;
@@ -131,9 +125,6 @@ void display_init()
     /* Initialise backlight driver */
     backlight_init();
 
-    /* Clear framebuffer, setting all pixels to 0x00 makes the screen white */
-    memset(frameBuffer, 0x00, CONFIG_SCREEN_WIDTH * CONFIG_SCREEN_HEIGHT * sizeof(uint16_t));
-
     /*
      * Turn on DMA2 and configure its interrupt. DMA is used to transfer the
      * framebuffer content to the screen without using CPU.
@@ -442,7 +433,7 @@ void display_terminate()
     __DSB();
 }
 
-void display_renderRows(uint8_t startRow, uint8_t endRow)
+void display_renderRows(uint8_t startRow, uint8_t endRow, void *fb)
 {
     /*
      * Put screen data lines back to alternate function mode, since they are in
@@ -465,6 +456,7 @@ void display_renderRows(uint8_t startRow, uint8_t endRow)
      * the CS pin low, in this way user code calling the renderingInProgress
      * function gets true as return value and does not stomp our work.
      */
+    uint16_t *frameBuffer = (uint16_t *) fb;
     for(uint8_t y = startRow; y < endRow; y++)
     {
         for(uint8_t x = 0; x < CONFIG_SCREEN_WIDTH; x++)
@@ -519,14 +511,9 @@ void display_renderRows(uint8_t startRow, uint8_t endRow)
     }
 }
 
-void display_render()
+void display_render(void *fb)
 {
-    display_renderRows(0, CONFIG_SCREEN_HEIGHT);
-}
-
-void *display_getFrameBuffer()
-{
-    return (void *)(frameBuffer);
+    display_renderRows(0, CONFIG_SCREEN_HEIGHT, fb);
 }
 
 void display_setContrast(uint8_t contrast)
diff --git a/platform/mcu/STM32F4xx/linker_script_MDx.ld b/platform/mcu/STM32F4xx/linker_script_MDx.ld
index 87dd7ff4..c544c522 100644
--- a/platform/mcu/STM32F4xx/linker_script_MDx.ld
+++ b/platform/mcu/STM32F4xx/linker_script_MDx.ld
@@ -164,10 +164,18 @@ SECTIONS
     } > smallram AT > flash
     _etext = LOADADDR(.data);
 
+    /* Put the display framebuffer in the "large" RAM, explicitly request to not
+       initialize it */
+    .bss2 (NOLOAD) :
+    {
+        *(.bss.fb)
+        . = ALIGN(8);
+    } > largeram
+
     /* .bss section: uninitialized global variables go to ram */
-    _bss_start = .;
     .bss :
     {
+        _bss_start = .;
         *(.bss)
         *(.bss.*)
         *(.gnu.linkonce.b.*)
@@ -175,14 +183,6 @@ SECTIONS
     } > smallram
     _bss_end = .;
 
-    /* Second BSS section located in the "large" RAM, explicitly request to not
-       initialize it */
-    .bss2 (NOLOAD) :
-    {
-        *(.bss2)
-        . = ALIGN(8);
-    } > largeram
-
     _end = .;
     PROVIDE(end = .);
 }