DMA2D signals transfer completion too soon?

[_Nick]

I used STM32CubeIDE to create the LCD_DSI_CmdMode_DoubleBuffer for the STM32F769I-DISCOVERY board. It works fine, but I made some modifications to just draw a rectangle: 

if 1
  BSP_LCD_SetTextColor(LCD_COLOR_RED);
  BSP_LCD_FillRect(0, 0, 800, 240);
#else
  /* Display example brief   */
  LCD_BriefDisplay();

  /* Copy Buffer 0 into buffer 1, so only image area to be redrawn later */
  CopyBuffer((uint32_t *)Buffers[0], (uint32_t *)Buffers[1], 0, 0, 800, 480);

  /*Draw first image */
  CopyBuffer((uint32_t *)Images[ImageIndex++], (uint32_t *)Buffers[front_buffer], 240, 160, 320, 240);
  pend_buffer = 0;
#endif

  /* Send Display On DCS Command to display */
  HAL_DSI_ShortWrite(&(hdsi_discovery),
                     0,
                     DSI_DCS_SHORT_PKT_WRITE_P1,
                     OTM8009A_CMD_DISPON,
                     0x00);

  /* Refresh the LCD display*/
  HAL_DSI_Refresh(&hdsi_discovery);

#if 1
  /* Infinite loop */
  while (1);
#else
  /* Infinite loop */
  while (1)
  {
    if(pend_buffer < 0)
    {
      /* Prepare back buffer */
      CopyBuffer((uint32_t *)Images[ImageIndex++], (uint32_t *)Buffers[1- front_buffer], 240, 160, 320, 240);
      pend_buffer = 1- front_buffer;

      if(ImageIndex >= 2)
      {
        ImageIndex = 0;
      }

      /* Refresh the display */
      HAL_DSI_Refresh(&hdsi_discovery);

      /* Wait some time before switching to next stage */
      HAL_Delay(2000);
    }
  }
#endif

 However the red rectangle is only partially drawn (it's supposed to take up half the screen): 

If I put a HAL_Delay before the refresh, it draws the whole rectangle. This suggests the DMA2D isn't finishing the transfer to the framebuffer even though it says it is (HAL_DMA2D_PollForTransfer() is returning in LL_FillBuffer()), but I'm really not sure as I'm pretty new to this stuff.

Thanks in advance.

 

[_Nick · Accepted solution]

Turns out if I add a delay right after turning on the display, it works fine: 

  /* Send Display On DCS Command to display */
  HAL_DSI_ShortWrite(&(hdsi_discovery),
                     0,
                     DSI_DCS_SHORT_PKT_WRITE_P1,
                     OTM8009A_CMD_DISPON,
                     0x00);
  HAL_Delay(1);

  BSP_LCD_SetTextColor(LCD_COLOR_BLUE);
  BSP_LCD_FillRect(0, 0, 800, 240);

  /* Refresh the LCD display*/
  HAL_DSI_Refresh(&hdsi_discovery);

 My guess is that there's an issue with the refresh occurring so soon after turning on the display.