2D Direct Memory Access (DMA2D) Support

The DMA2D peripheral of chips like the ESP32-P4 copies 2-D data without CPU intervention. The Espressif LVGL port uses it to move rendered buffers to the display.

Overview

Some Espressif chips, such as the ESP32-P4 family, feature a peripheral that speeds up copying 2-D data from one place to another, including sending that 2-D data to other peripherals.

This peripheral is the 2-D direct memory access, or DMA2D. ESP-IDF offers a full-featured driver for it that is automatically enabled on the supported chips.

One of its primary roles is to support the Pixel Processing Accelerator (PPA): it copies the source image data to the desired PPA client, splitting the data into fixed size blocks called bursts. The DMA2D is also used to pick the output chunks from the PPA client and copy them to the destination buffer, or the display frame buffer.

More information about PPA can be found in: PPA (Pixel Processing Accelerator) Support.

Interacting with the DMA2D

LVGL does not interact with the DMA2D directly. Instead, the display driver of the Espressif LVGL port component uses the DMA2D to copy the drawn buffer to the display buffer without CPU intervention. This has to be enabled explicitly on the display driver of the port component.

To enable it, set CONFIG_BSP_DISPLAY_LVGL_AVOID_TEAR in your sdkconfig.defaults, which tells the driver to use the DMA2D to optimize the transfer.

If you configure the display manually, the DMA2D can be enabled at runtime by setting the DMA2D flag to true:

/* Gets the default configuration for the MIPI display controller */
esp_lcd_dpi_panel_config_t dpi_config = EK79007_1024_600_PANEL_60HZ_CONFIG(LCD_COLOR_PIXEL_FORMAT_RGB888);

/* Explicitly set the DMA2D to assist the buffer transfer */
dpi_config.flags.use_dma2d = true;

ek79007_vendor_config_t vendor_config = {
    .mipi_config = {
        .dsi_bus = mipi_dsi_bus,
        .dpi_config = &dpi_config,
    },
};

esp_lcd_panel_dev_config_t lcd_dev_config = {
    .reset_gpio_num = UI_FIRMWARE_PIN_NUM_LCD_RST,
    .rgb_ele_order = LCD_RGB_ELEMENT_ORDER_RGB,
    .bits_per_pixel = 24,
    .vendor_config = &vendor_config,
};

/* Configures and enable the display */
ESP_ERROR_CHECK(esp_lcd_new_panel_ek79007(mipi_dbi_io, &lcd_dev_config, &mipi_dpi_panel));