esp-idf/components/esp_lcd/src/esp_lcd_rgb_panel.c

/*
 * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <stdlib.h>
#include <sys/cdefs.h>
#include <sys/param.h>
#include <string.h>
#include "sdkconfig.h"
#if CONFIG_LCD_ENABLE_DEBUG_LOG
// The local log level must be defined before including esp_log.h
// Set the maximum log level for this source file
#define LOG_LOCAL_LEVEL ESP_LOG_DEBUG
#endif
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "esp_attr.h"
#include "esp_check.h"
#include "esp_pm.h"
#include "esp_lcd_panel_interface.h"
#include "esp_lcd_panel_rgb.h"
#include "esp_lcd_panel_ops.h"
#include "esp_rom_gpio.h"
#include "soc/soc_caps.h"
#include "esp_private/esp_clk.h"
#include "hal/dma_types.h"
#include "hal/gpio_hal.h"
#include "esp_private/gdma.h"
#include "driver/gpio.h"
#include "esp_private/periph_ctrl.h"
#if CONFIG_SPIRAM
#include "esp_psram.h"
#endif
#include "esp_lcd_common.h"
#include "soc/lcd_periph.h"
#include "hal/lcd_hal.h"
#include "hal/lcd_ll.h"
#include <rom/cache.h>

#if CONFIG_LCD_RGB_ISR_IRAM_SAFE
#define LCD_RGB_INTR_ALLOC_FLAGS     (ESP_INTR_FLAG_IRAM | ESP_INTR_FLAG_INTRDISABLED)
#else
#define LCD_RGB_INTR_ALLOC_FLAGS     ESP_INTR_FLAG_INTRDISABLED
#endif

static const char *TAG = "lcd_panel.rgb";

typedef struct esp_rgb_panel_t esp_rgb_panel_t;


static esp_err_t rgb_panel_del(esp_lcd_panel_t *panel);
static esp_err_t rgb_panel_reset(esp_lcd_panel_t *panel);
static esp_err_t rgb_panel_init(esp_lcd_panel_t *panel);
static esp_err_t rgb_panel_draw_bitmap(esp_lcd_panel_t *panel, int x_start, int y_start, int x_end, int y_end, const void *color_data);
static esp_err_t rgb_panel_invert_color(esp_lcd_panel_t *panel, bool invert_color_data);
static esp_err_t rgb_panel_mirror(esp_lcd_panel_t *panel, bool mirror_x, bool mirror_y);
static esp_err_t rgb_panel_swap_xy(esp_lcd_panel_t *panel, bool swap_axes);
static esp_err_t rgb_panel_set_gap(esp_lcd_panel_t *panel, int x_gap, int y_gap);
static esp_err_t rgb_panel_disp_on_off(esp_lcd_panel_t *panel, bool off);
static esp_err_t lcd_rgb_panel_select_clock_src(esp_rgb_panel_t *panel, lcd_clock_source_t clk_src);
static esp_err_t lcd_rgb_panel_create_trans_link(esp_rgb_panel_t *panel);
static esp_err_t lcd_rgb_panel_configure_gpio(esp_rgb_panel_t *panel, const esp_lcd_rgb_panel_config_t *panel_config);
static void lcd_rgb_panel_start_transmission(esp_rgb_panel_t *rgb_panel);
static void lcd_default_isr_handler(void *args);

struct esp_rgb_panel_t {
    esp_lcd_panel_t base;  // Base class of generic lcd panel
    int panel_id;          // LCD panel ID
    lcd_hal_context_t hal; // Hal layer object
    size_t data_width;     // Number of data lines (e.g. for RGB565, the data width is 16)
    size_t sram_trans_align;  // Alignment for framebuffer that allocated in SRAM
    size_t psram_trans_align; // Alignment for framebuffer that allocated in PSRAM
    int disp_gpio_num;     // Display control GPIO, which is used to perform action like "disp_off"
    intr_handle_t intr;    // LCD peripheral interrupt handle
    esp_pm_lock_handle_t pm_lock; // Power management lock
    size_t num_dma_nodes;  // Number of DMA descriptors that used to carry the frame buffer
    uint8_t *fb;           // Frame buffer
    size_t fb_size;        // Size of frame buffer
    int data_gpio_nums[SOC_LCD_RGB_DATA_WIDTH]; // GPIOs used for data lines, we keep these GPIOs for action like "invert_color"
    uint32_t src_clk_hz;   // Peripheral source clock resolution
    esp_lcd_rgb_timing_t timings;   // RGB timing parameters (e.g. pclk, sync pulse, porch width)
    gdma_channel_handle_t dma_chan; // DMA channel handle
    int bounce_buffer_size_bytes;   //If not-zero, the driver uses a bounce buffer in internal memory to DMA from. It's in bytes here.
    uint8_t *bounce_buffer[2];      //Pointer to the bounce buffers
    int bounce_buf_frame_start;     //If frame restarts, which bb has the initial frame data?
    int bounce_pos_px;                 // Position in whatever source material is used for the bounce buffer, in pixels
    esp_lcd_rgb_panel_vsync_cb_t on_vsync; // VSYNC event callback
    esp_lcd_rgb_panel_bounce_buf_fill_cb_t on_bounce_empty; // callback used to fill a bounce buffer rather than copying from the frame buffer
    void *user_ctx;                 // Reserved user's data of callback functions
    int x_gap;                      // Extra gap in x coordinate, it's used when calculate the flush window
    int y_gap;                      // Extra gap in y coordinate, it's used when calculate the flush window
    portMUX_TYPE spinlock;          // to protect panel specific resource from concurrent access (e.g. between task and ISR)
    struct {
        unsigned int disp_en_level: 1; // The level which can turn on the screen by `disp_gpio_num`
        unsigned int stream_mode: 1;   // If set, the LCD transfers data continuously, otherwise, it stops refreshing the LCD when transaction done
        unsigned int fb_in_psram: 1;   // Whether the frame buffer is in PSRAM
        unsigned int need_update_pclk: 1; // Whether to update the PCLK before start a new transaction
        unsigned int bb_do_cache_invalidate: 1; //If we do cache invalidate in bb psram fb mode
    } flags;
    dma_descriptor_t dma_restart_node; //DMA descriptor used to restart the transfer
    dma_descriptor_t dma_nodes[]; // DMA descriptor pool of size `num_dma_nodes`
};




esp_err_t esp_lcd_new_rgb_panel(const esp_lcd_rgb_panel_config_t *rgb_panel_config, esp_lcd_panel_handle_t *ret_panel)
{
#if CONFIG_LCD_ENABLE_DEBUG_LOG
    esp_log_level_set(TAG, ESP_LOG_DEBUG);
#endif
    esp_err_t ret = ESP_OK;
    esp_rgb_panel_t *rgb_panel = NULL;
    ESP_GOTO_ON_FALSE(rgb_panel_config && ret_panel, ESP_ERR_INVALID_ARG, err, TAG, "invalid parameter");
    ESP_GOTO_ON_FALSE(rgb_panel_config->data_width == 16, ESP_ERR_NOT_SUPPORTED, err, TAG,
                      "unsupported data width %d", rgb_panel_config->data_width);
    ESP_GOTO_ON_FALSE(!(rgb_panel_config->bounce_buffer_size_px == 0 && rgb_panel_config->on_bounce_empty != NULL),
                      ESP_ERR_INVALID_ARG, err, TAG, "cannot have bounce empty callback without having a bounce buffer");
    ESP_GOTO_ON_FALSE(!(rgb_panel_config->bounce_buffer_size_px != 0 && rgb_panel_config->on_bounce_empty == NULL &&
                      !rgb_panel_config->flags.fb_in_psram), ESP_ERR_INVALID_ARG, err, TAG,
                      "bounce buffer without callback and main fb not in psram does not make sense");

#if CONFIG_LCD_RGB_ISR_IRAM_SAFE
    if (rgb_panel_config->on_frame_trans_done) {
        ESP_RETURN_ON_FALSE(esp_ptr_in_iram(rgb_panel_config->on_frame_trans_done), ESP_ERR_INVALID_ARG, TAG, "on_frame_trans_done callback not in IRAM");
    }
    if (rgb_panel_config->user_ctx) {
        ESP_RETURN_ON_FALSE(esp_ptr_internal(rgb_panel_config->user_ctx), ESP_ERR_INVALID_ARG, TAG, "user context not in internal RAM");
    }
#endif

    // calculate the number of DMA descriptors
    size_t fb_size = rgb_panel_config->timings.h_res * rgb_panel_config->timings.v_res * rgb_panel_config->data_width / 8;
    size_t num_dma_nodes;
    int bounce_bytes = 0;
    if (rgb_panel_config->bounce_buffer_size_px == 0) {
        // No bounce buffers. DMA descriptors need to fit entire framebuffer
        num_dma_nodes = (fb_size + DMA_DESCRIPTOR_BUFFER_MAX_SIZE - 1) / DMA_DESCRIPTOR_BUFFER_MAX_SIZE;
    } else {
        //The FB needs to be an integer multiple of the size of a bounce buffer (so
        //we end on the end of the second bounce buffer). Adjust the size of the
        //bounce buffers if it is not.
        int pixel_data_bytes = rgb_panel_config->data_width / 8; //size of one pixel, in bytes
        int no_pixels = rgb_panel_config->timings.h_res * rgb_panel_config->timings.v_res;
        bounce_bytes = rgb_panel_config->bounce_buffer_size_px * pixel_data_bytes;
        if (no_pixels % (rgb_panel_config->bounce_buffer_size_px * pixel_data_bytes)) {
            //Search for some value that does work. Yes, this is a stupidly simple algo, but it only
            //needs to run on startup.
            for (int a=rgb_panel_config->bounce_buffer_size_px; a>0; a--) {
                if ((no_pixels % (a * pixel_data_bytes))==0) {
                    bounce_bytes = a * pixel_data_bytes;
                    ESP_LOGW(TAG, "Frame buffer is not an integer multiple of bounce buffers.");
                    ESP_LOGW(TAG, "Adjusted bounce buffer size from %d to %d pixels to fix this.",
                                rgb_panel_config->bounce_buffer_size_px, bounce_bytes/pixel_data_bytes);
                    break;
                }
            }
        }

        // DMA descriptors need to fit both bounce buffers
        num_dma_nodes = (bounce_bytes + DMA_DESCRIPTOR_BUFFER_MAX_SIZE - 1) / DMA_DESCRIPTOR_BUFFER_MAX_SIZE;
        num_dma_nodes = num_dma_nodes * 2; //as we have two bounce buffers
    }
    // DMA descriptors must be placed in internal SRAM (requested by DMA)
    rgb_panel = heap_caps_calloc(1, sizeof(esp_rgb_panel_t) + num_dma_nodes * sizeof(dma_descriptor_t), MALLOC_CAP_DMA | MALLOC_CAP_INTERNAL);
    ESP_GOTO_ON_FALSE(rgb_panel, ESP_ERR_NO_MEM, err, TAG, "no mem for rgb panel");
    rgb_panel->num_dma_nodes = num_dma_nodes;
    rgb_panel->panel_id = -1;
    // register to platform
    int panel_id = lcd_com_register_device(LCD_COM_DEVICE_TYPE_RGB, rgb_panel);
    ESP_GOTO_ON_FALSE(panel_id >= 0, ESP_ERR_NOT_FOUND, err, TAG, "no free rgb panel slot");
    rgb_panel->panel_id = panel_id;
    rgb_panel->bounce_buffer_size_bytes = bounce_bytes;
    // enable APB to access LCD registers
    periph_module_enable(lcd_periph_signals.panels[panel_id].module);
    periph_module_reset(lcd_periph_signals.panels[panel_id].module);
    // alloc frame buffer
    bool alloc_from_psram = false;
    // fb_in_psram is only an option, if there's no PSRAM on board, we still alloc from SRAM
    if (rgb_panel_config->flags.fb_in_psram) {
#if CONFIG_SPIRAM_USE_MALLOC || CONFIG_SPIRAM_USE_CAPS_ALLOC
        if (esp_psram_is_initialized()) {
            alloc_from_psram = true;
        }
#endif
    }
    size_t psram_trans_align = rgb_panel_config->psram_trans_align ? rgb_panel_config->psram_trans_align : 64;
    size_t sram_trans_align = rgb_panel_config->sram_trans_align ? rgb_panel_config->sram_trans_align : 4;
    rgb_panel->fb_size = fb_size;
    if (!rgb_panel_config->on_bounce_empty) {
        //We need to allocate a framebuffer.
        if (alloc_from_psram) {
            // the low level malloc function will help check the validation of alignment
            rgb_panel->fb = heap_caps_aligned_calloc(psram_trans_align, 1, fb_size, MALLOC_CAP_SPIRAM | MALLOC_CAP_8BIT);
        } else {
            rgb_panel->fb = heap_caps_aligned_calloc(sram_trans_align, 1, fb_size, MALLOC_CAP_INTERNAL | MALLOC_CAP_DMA);
        }
        ESP_GOTO_ON_FALSE(rgb_panel->fb, ESP_ERR_NO_MEM, err, TAG, "no mem for frame buffer");
        rgb_panel->psram_trans_align = psram_trans_align;
        rgb_panel->sram_trans_align = sram_trans_align;
        rgb_panel->flags.fb_in_psram = alloc_from_psram;
    }
    if (rgb_panel->bounce_buffer_size_bytes) {
        //We need to allocate bounce buffers.
        rgb_panel->bounce_buffer[0] = heap_caps_aligned_calloc(sram_trans_align, 1,
                        rgb_panel->bounce_buffer_size_bytes, MALLOC_CAP_INTERNAL | MALLOC_CAP_DMA);
        rgb_panel->bounce_buffer[1] = heap_caps_aligned_calloc(sram_trans_align, 1,
                        rgb_panel->bounce_buffer_size_bytes, MALLOC_CAP_INTERNAL | MALLOC_CAP_DMA);
    }
    if (rgb_panel_config->on_bounce_empty) {
        rgb_panel->on_bounce_empty = rgb_panel_config->on_bounce_empty;
        rgb_panel->bounce_buffer_cb_user_ctx = rgb_panel_config->bounce_buffer_cb_user_ctx;
    }
    // initialize HAL layer, so we can call LL APIs later
    lcd_hal_init(&rgb_panel->hal, panel_id);
    // enable clock gating
    lcd_ll_enable_clock(rgb_panel->hal.dev, true);
    // set clock source
    ret = lcd_rgb_panel_select_clock_src(rgb_panel, rgb_panel_config->clk_src);
    ESP_GOTO_ON_ERROR(ret, err, TAG, "set source clock failed");
    // install interrupt service, (LCD peripheral shares the interrupt source with Camera by different mask)
    int isr_flags = LCD_RGB_INTR_ALLOC_FLAGS | ESP_INTR_FLAG_SHARED;
    ret = esp_intr_alloc_intrstatus(lcd_periph_signals.panels[panel_id].irq_id, isr_flags,
                                    (uint32_t)lcd_ll_get_interrupt_status_reg(rgb_panel->hal.dev),
                                    LCD_LL_EVENT_VSYNC_END, lcd_default_isr_handler, rgb_panel, &rgb_panel->intr);
    ESP_GOTO_ON_ERROR(ret, err, TAG, "install interrupt failed");
    lcd_ll_enable_interrupt(rgb_panel->hal.dev, LCD_LL_EVENT_VSYNC_END, false); // disable all interrupts
    lcd_ll_clear_interrupt_status(rgb_panel->hal.dev, UINT32_MAX); // clear pending interrupt
    // install DMA service
    rgb_panel->flags.stream_mode = !rgb_panel_config->flags.relax_on_idle;
    ret = lcd_rgb_panel_create_trans_link(rgb_panel);
    ESP_GOTO_ON_ERROR(ret, err, TAG, "install DMA failed");
    // configure GPIO
    ret = lcd_rgb_panel_configure_gpio(rgb_panel, rgb_panel_config);
    ESP_GOTO_ON_ERROR(ret, err, TAG, "configure GPIO failed");
    // fill other rgb panel runtime parameters
    memcpy(rgb_panel->data_gpio_nums, rgb_panel_config->data_gpio_nums, SOC_LCD_RGB_DATA_WIDTH);
    rgb_panel->timings = rgb_panel_config->timings;
    rgb_panel->data_width = rgb_panel_config->data_width;
    rgb_panel->disp_gpio_num = rgb_panel_config->disp_gpio_num;
    rgb_panel->flags.disp_en_level = !rgb_panel_config->flags.disp_active_low;
    rgb_panel->flags.bb_do_cache_invalidate = rgb_panel_config->flags.bb_do_cache_invalidate;
    rgb_panel->on_frame_trans_done = rgb_panel_config->on_frame_trans_done;
    rgb_panel->user_ctx = rgb_panel_config->user_ctx;
    rgb_panel->spinlock = (portMUX_TYPE)portMUX_INITIALIZER_UNLOCKED;
    // fill function table
    rgb_panel->base.del = rgb_panel_del;
    rgb_panel->base.reset = rgb_panel_reset;
    rgb_panel->base.init = rgb_panel_init;
    rgb_panel->base.draw_bitmap = rgb_panel_draw_bitmap;
    rgb_panel->base.disp_on_off = rgb_panel_disp_on_off;
    rgb_panel->base.invert_color = rgb_panel_invert_color;
    rgb_panel->base.mirror = rgb_panel_mirror;
    rgb_panel->base.swap_xy = rgb_panel_swap_xy;
    rgb_panel->base.set_gap = rgb_panel_set_gap;
    // return base class
    *ret_panel = &(rgb_panel->base);
    ESP_LOGD(TAG, "new rgb panel(%d) @%p, fb @%p, size=%zu", rgb_panel->panel_id, rgb_panel, rgb_panel->fb, rgb_panel->fb_size);
    return ESP_OK;

err:
    if (rgb_panel) {
        if (rgb_panel->panel_id >= 0) {
            periph_module_disable(lcd_periph_signals.panels[rgb_panel->panel_id].module);
            lcd_com_remove_device(LCD_COM_DEVICE_TYPE_RGB, rgb_panel->panel_id);
        }
        if (rgb_panel->fb) {
            free(rgb_panel->fb);
        }
        if (rgb_panel->dma_chan) {
            gdma_disconnect(rgb_panel->dma_chan);
            gdma_del_channel(rgb_panel->dma_chan);
        }
        if (rgb_panel->intr) {
            esp_intr_free(rgb_panel->intr);
        }
        if (rgb_panel->pm_lock) {
            esp_pm_lock_release(rgb_panel->pm_lock);
            esp_pm_lock_delete(rgb_panel->pm_lock);
        }
        free(rgb_panel);
    }
    return ret;
}

esp_err_t esp_rgb_panel_set_pclk(esp_lcd_panel_handle_t panel, uint32_t freq_hz)
esp_err_t esp_lcd_rgb_panel_register_event_callbacks(esp_lcd_panel_handle_t panel, const esp_lcd_rgb_panel_event_callbacks_t *callbacks, void *user_ctx)
{
    ESP_RETURN_ON_FALSE(panel && callbacks, ESP_ERR_INVALID_ARG, TAG, "invalid argument");
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
#if CONFIG_LCD_RGB_ISR_IRAM_SAFE
    if (callbacks->on_vsync) {
        ESP_RETURN_ON_FALSE(esp_ptr_in_iram(callbacks->on_vsync), ESP_ERR_INVALID_ARG, TAG, "on_vsync callback not in IRAM");
    }
    if (callbacks->on_bounce_empty) {
        ESP_RETURN_ON_FALSE(esp_ptr_in_iram(callbacks->on_bounce_empty), ESP_ERR_INVALID_ARG, TAG, "on_bounce_empty callback not in IRAM");
    }
    if (user_ctx) {
        ESP_RETURN_ON_FALSE(esp_ptr_internal(user_ctx), ESP_ERR_INVALID_ARG, TAG, "user context not in internal RAM");
    }
#endif // CONFIG_LCD_RGB_ISR_IRAM_SAFE
    rgb_panel->on_vsync = callbacks->on_vsync;
    rgb_panel->on_bounce_empty = callbacks->on_bounce_empty;
    rgb_panel->user_ctx = user_ctx;
    return ESP_OK;
}

{
    ESP_RETURN_ON_FALSE(panel, ESP_ERR_INVALID_ARG, TAG, "invalid argument");
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    // the pclk frequency will be updated in `lcd_rgb_panel_start_transmission()`
    portENTER_CRITICAL(&rgb_panel->spinlock);
    rgb_panel->flags.need_update_pclk = true;
    rgb_panel->timings.pclk_hz = freq_hz;
    portEXIT_CRITICAL(&rgb_panel->spinlock);
    return ESP_OK;
}

static esp_err_t rgb_panel_del(esp_lcd_panel_t *panel)
{
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    int panel_id = rgb_panel->panel_id;
    gdma_disconnect(rgb_panel->dma_chan);
    gdma_del_channel(rgb_panel->dma_chan);
    esp_intr_free(rgb_panel->intr);
    lcd_ll_enable_clock(rgb_panel->hal.dev, false);
    periph_module_disable(lcd_periph_signals.panels[panel_id].module);
    lcd_com_remove_device(LCD_COM_DEVICE_TYPE_RGB, rgb_panel->panel_id);
    free(rgb_panel->bounce_buffer[0]);
    free(rgb_panel->bounce_buffer[1]);
    free(rgb_panel->fb);
    if (rgb_panel->pm_lock) {
        esp_pm_lock_release(rgb_panel->pm_lock);
        esp_pm_lock_delete(rgb_panel->pm_lock);
    }
    free(rgb_panel);
    ESP_LOGD(TAG, "del rgb panel(%d)", panel_id);
    return ESP_OK;
}

static esp_err_t rgb_panel_reset(esp_lcd_panel_t *panel)
{
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    lcd_ll_fifo_reset(rgb_panel->hal.dev);
    lcd_ll_reset(rgb_panel->hal.dev);
    return ESP_OK;
}

static esp_err_t rgb_panel_init(esp_lcd_panel_t *panel)
{
    esp_err_t ret = ESP_OK;
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    // set pixel clock frequency
    rgb_panel->timings.pclk_hz = lcd_hal_cal_pclk_freq(&rgb_panel->hal, rgb_panel->src_clk_hz, rgb_panel->timings.pclk_hz);
    // pixel clock phase and polarity
    lcd_ll_set_clock_idle_level(rgb_panel->hal.dev, rgb_panel->timings.flags.pclk_idle_high);
    lcd_ll_set_pixel_clock_edge(rgb_panel->hal.dev, rgb_panel->timings.flags.pclk_active_neg);
    // enable RGB mode and set data width
    lcd_ll_enable_rgb_mode(rgb_panel->hal.dev, true);
    lcd_ll_set_data_width(rgb_panel->hal.dev, rgb_panel->data_width);
    lcd_ll_set_phase_cycles(rgb_panel->hal.dev, 0, 0, 1); // enable data phase only
    // number of data cycles is controlled by DMA buffer size
    lcd_ll_enable_output_always_on(rgb_panel->hal.dev, true);
    // configure HSYNC, VSYNC, DE signal idle state level
    lcd_ll_set_idle_level(rgb_panel->hal.dev, !rgb_panel->timings.flags.hsync_idle_low,
                          !rgb_panel->timings.flags.vsync_idle_low, rgb_panel->timings.flags.de_idle_high);
    // configure blank region timing
    lcd_ll_set_blank_cycles(rgb_panel->hal.dev, 1, 1); // RGB panel always has a front and back blank (porch region)
    lcd_ll_set_horizontal_timing(rgb_panel->hal.dev, rgb_panel->timings.hsync_pulse_width,
                                 rgb_panel->timings.hsync_back_porch, rgb_panel->timings.h_res,
                                 rgb_panel->timings.hsync_front_porch);
    lcd_ll_set_vertical_timing(rgb_panel->hal.dev, rgb_panel->timings.vsync_pulse_width,
                               rgb_panel->timings.vsync_back_porch, rgb_panel->timings.v_res,
                               rgb_panel->timings.vsync_front_porch);
    // output hsync even in porch region
    lcd_ll_enable_output_hsync_in_porch_region(rgb_panel->hal.dev, true);
    // generate the hsync at the very begining of line
    lcd_ll_set_hsync_position(rgb_panel->hal.dev, 0);
    // restart flush by hardware has some limitation, instead, the driver will restart the flush in the VSYNC end interrupt by software
    lcd_ll_enable_auto_next_frame(rgb_panel->hal.dev, false);
    // trigger interrupt on the end of frame
    lcd_ll_enable_interrupt(rgb_panel->hal.dev, LCD_LL_EVENT_VSYNC_END, true);
    // enable intr
    esp_intr_enable(rgb_panel->intr);
    // start transmission
    if (rgb_panel->flags.stream_mode) {
        lcd_rgb_panel_start_transmission(rgb_panel);
    }
    ESP_LOGD(TAG, "rgb panel(%d) start, pclk=%uHz", rgb_panel->panel_id, rgb_panel->timings.pclk_hz);
    return ret;
}

static esp_err_t rgb_panel_draw_bitmap(esp_lcd_panel_t *panel, int x_start, int y_start, int x_end, int y_end, const void *color_data)
{
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    if (rgb_panel->fb == NULL) {
        //Can't draw a bitmap to a non-existing framebuffer.
        //This happens when e.g. we use an external callback to refill the bounce buffers.
        return ESP_ERR_NOT_SUPPORTED;
    }
    assert((x_start < x_end) && (y_start < y_end) && "start position must be smaller than end position");
    // adjust the flush window by adding extra gap
    x_start += rgb_panel->x_gap;
    y_start += rgb_panel->y_gap;
    x_end += rgb_panel->x_gap;
    y_end += rgb_panel->y_gap;
    // round the boundary
    x_start = MIN(x_start, rgb_panel->timings.h_res);
    x_end = MIN(x_end, rgb_panel->timings.h_res);
    y_start = MIN(y_start, rgb_panel->timings.v_res);
    y_end = MIN(y_end, rgb_panel->timings.v_res);

    // convert the frame buffer to 3D array
    int bytes_per_pixel = rgb_panel->data_width / 8;
    int pixels_per_line = rgb_panel->timings.h_res;
    uint32_t bytes_per_line = bytes_per_pixel * pixels_per_line;
    const uint8_t *from = (const uint8_t *)color_data;
    // manipulate the frame buffer
    uint32_t copy_bytes_per_line = (x_end - x_start) * bytes_per_pixel;
    uint8_t *to = rgb_panel->fb + (y_start * pixels_per_line + x_start) * bytes_per_pixel;
    for (int y = y_start; y < y_end; y++) {
        memcpy(to, from, copy_bytes_per_line);
        to += bytes_per_line;
        from += copy_bytes_per_line;
    }
    if (rgb_panel->flags.fb_in_psram && !rgb_panel->bounce_buffer_size_bytes) {
        // CPU writes data to PSRAM through DCache, data in PSRAM might not get updated, so write back
        // Note that if we use a bounce buffer, the data gets read by the CPU as well so no need to write back.
        uint32_t bytes_to_flush = (y_end - y_start) * bytes_per_line;
        Cache_WriteBack_Addr((uint32_t)(rgb_panel->fb + y_start * bytes_per_line), bytes_to_flush);
    }

    // restart the new transmission
    if (!rgb_panel->flags.stream_mode) {
        lcd_rgb_panel_start_transmission(rgb_panel);
    }

    return ESP_OK;
}

static esp_err_t rgb_panel_invert_color(esp_lcd_panel_t *panel, bool invert_color_data)
{
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    int panel_id = rgb_panel->panel_id;
    // inverting the data line by GPIO matrix
    for (int i = 0; i < rgb_panel->data_width; i++) {
        esp_rom_gpio_connect_out_signal(rgb_panel->data_gpio_nums[i], lcd_periph_signals.panels[panel_id].data_sigs[i],
                                        invert_color_data, false);
    }
    return ESP_OK;
}

static esp_err_t rgb_panel_mirror(esp_lcd_panel_t *panel, bool mirror_x, bool mirror_y)
{
    return ESP_ERR_NOT_SUPPORTED;
}

static esp_err_t rgb_panel_swap_xy(esp_lcd_panel_t *panel, bool swap_axes)
{
    return ESP_ERR_NOT_SUPPORTED;
}

static esp_err_t rgb_panel_set_gap(esp_lcd_panel_t *panel, int x_gap, int y_gap)
{
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    rgb_panel->x_gap = x_gap;
    rgb_panel->x_gap = y_gap;
    return ESP_OK;
}

static esp_err_t rgb_panel_disp_on_off(esp_lcd_panel_t *panel, bool on_off)
{
    esp_rgb_panel_t *rgb_panel = __containerof(panel, esp_rgb_panel_t, base);
    if (rgb_panel->disp_gpio_num < 0) {
        return ESP_ERR_NOT_SUPPORTED;
    }
    if (!on_off) { // turn off screen
        gpio_set_level(rgb_panel->disp_gpio_num, !rgb_panel->flags.disp_en_level);
    } else { // turn on screen
        gpio_set_level(rgb_panel->disp_gpio_num, rgb_panel->flags.disp_en_level);
    }
    return ESP_OK;
}

static esp_err_t lcd_rgb_panel_configure_gpio(esp_rgb_panel_t *panel, const esp_lcd_rgb_panel_config_t *panel_config)
{
    int panel_id = panel->panel_id;
    // check validation of GPIO number
    bool valid_gpio = (panel_config->pclk_gpio_num >= 0);
    if (panel_config->de_gpio_num < 0) {
        // Hsync and Vsync are required in HV mode
        valid_gpio = valid_gpio && (panel_config->hsync_gpio_num >= 0) && (panel_config->vsync_gpio_num >= 0);
    }
    for (size_t i = 0; i < panel_config->data_width; i++) {
        valid_gpio = valid_gpio && (panel_config->data_gpio_nums[i] >= 0);
    }
    if (!valid_gpio) {
        return ESP_ERR_INVALID_ARG;
    }
    // connect peripheral signals via GPIO matrix
    for (size_t i = 0; i < panel_config->data_width; i++) {
        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[panel_config->data_gpio_nums[i]], PIN_FUNC_GPIO);
        gpio_set_direction(panel_config->data_gpio_nums[i], GPIO_MODE_OUTPUT);
        esp_rom_gpio_connect_out_signal(panel_config->data_gpio_nums[i],
                                        lcd_periph_signals.panels[panel_id].data_sigs[i], false, false);
    }
    if (panel_config->hsync_gpio_num >= 0) {
        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[panel_config->hsync_gpio_num], PIN_FUNC_GPIO);
        gpio_set_direction(panel_config->hsync_gpio_num, GPIO_MODE_OUTPUT);
        esp_rom_gpio_connect_out_signal(panel_config->hsync_gpio_num,
                                        lcd_periph_signals.panels[panel_id].hsync_sig, false, false);
    }
    if (panel_config->vsync_gpio_num >= 0) {
        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[panel_config->vsync_gpio_num], PIN_FUNC_GPIO);
        gpio_set_direction(panel_config->vsync_gpio_num, GPIO_MODE_OUTPUT);
        esp_rom_gpio_connect_out_signal(panel_config->vsync_gpio_num,
                                        lcd_periph_signals.panels[panel_id].vsync_sig, false, false);
    }
    gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[panel_config->pclk_gpio_num], PIN_FUNC_GPIO);
    gpio_set_direction(panel_config->pclk_gpio_num, GPIO_MODE_OUTPUT);
    esp_rom_gpio_connect_out_signal(panel_config->pclk_gpio_num,
                                    lcd_periph_signals.panels[panel_id].pclk_sig, false, false);
    // DE signal might not be necessary for some RGB LCD
    if (panel_config->de_gpio_num >= 0) {
        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[panel_config->de_gpio_num], PIN_FUNC_GPIO);
        gpio_set_direction(panel_config->de_gpio_num, GPIO_MODE_OUTPUT);
        esp_rom_gpio_connect_out_signal(panel_config->de_gpio_num,
                                        lcd_periph_signals.panels[panel_id].de_sig, false, false);
    }
    // disp enable GPIO is optional
    if (panel_config->disp_gpio_num >= 0) {
        gpio_hal_iomux_func_sel(GPIO_PIN_MUX_REG[panel_config->disp_gpio_num], PIN_FUNC_GPIO);
        gpio_set_direction(panel_config->disp_gpio_num, GPIO_MODE_OUTPUT);
        esp_rom_gpio_connect_out_signal(panel_config->disp_gpio_num, SIG_GPIO_OUT_IDX, false, false);
    }
    return ESP_OK;
}

static esp_err_t lcd_rgb_panel_select_clock_src(esp_rgb_panel_t *panel, lcd_clock_source_t clk_src)
{
    esp_err_t ret = ESP_OK;
    switch (clk_src) {
    case LCD_CLK_SRC_PLL160M:
        panel->src_clk_hz = 160000000;
#if CONFIG_PM_ENABLE
        ret = esp_pm_lock_create(ESP_PM_APB_FREQ_MAX, 0, "rgb_panel", &panel->pm_lock);
        ESP_RETURN_ON_ERROR(ret, TAG, "create ESP_PM_APB_FREQ_MAX lock failed");
        // hold the lock during the whole lifecycle of RGB panel
        esp_pm_lock_acquire(panel->pm_lock);
        ESP_LOGD(TAG, "installed ESP_PM_APB_FREQ_MAX lock and hold the lock during the whole panel lifecycle");
#endif
        break;
    case LCD_CLK_SRC_XTAL:
        panel->src_clk_hz = esp_clk_xtal_freq();
        break;
    default:
        ESP_RETURN_ON_FALSE(false, ESP_ERR_NOT_SUPPORTED, TAG, "unsupported clock source: %d", clk_src);
        break;
    }
    lcd_ll_select_clk_src(panel->hal.dev, clk_src);
    return ret;
}

static IRAM_ATTR bool lcd_rgb_panel_fill_bounce_buffer(esp_rgb_panel_t *panel, uint8_t *buffer)
{
    bool need_yield = false;
    int bytes_per_pixel = panel->data_width / 8;
    if (panel->on_bounce_empty) {
        //We don't have a framebuffer here; we need to call a callback to refill the bounce buffer
        //for us.
        need_yield=panel->on_bounce_empty((void*)buffer, panel->bounce_pos_px,
                    panel->bounce_buffer_size_bytes, panel->bounce_buffer_cb_user_ctx);
    } else {
        //We do have a framebuffer; copy from there.
        memcpy(buffer, &panel->fb[panel->bounce_pos_px * bytes_per_pixel], panel->bounce_buffer_size_bytes);
        if (panel->flags.bb_do_cache_invalidate) {
            //We don't need the bytes we copied from psram anymore.
            //Make sure that if anything happened to have changed (because the line already was in cache) we write
            //the data back.
            Cache_WriteBack_Addr((uint32_t)&panel->fb[panel->bounce_pos_px * bytes_per_pixel], panel->bounce_buffer_size_bytes);
            //Invalidate the data. Note: possible race: perhaps something on the other core can squeeze a write
            //between this and the writeback, in which case that data gets discarded.
            Cache_Invalidate_Addr((uint32_t)&panel->fb[panel->bounce_pos_px * bytes_per_pixel], panel->bounce_buffer_size_bytes);
        }
    }
    panel->bounce_pos_px+=panel->bounce_buffer_size_bytes / bytes_per_pixel;
    //If the bounce pos is larger than the framebuffer size, wrap around so the next isr starts pre-loading
    //the next frame.
    if (panel->bounce_pos_px >= panel->fb_size / bytes_per_pixel) {
        panel->bounce_pos_px=0;
    }
    if (!panel->on_bounce_empty) {
        //Preload the next bit of buffer into psram.
        Cache_Start_DCache_Preload((uint32_t)&panel->fb[panel->bounce_pos_px * bytes_per_pixel],
                    panel->bounce_buffer_size_bytes, 0);
    }
    return need_yield;
}

//This is called in bounce buffer mode, when one bounce buffer has been fully sent to the LCD peripheral.
static IRAM_ATTR bool lcd_rgb_panel_eof_handler(gdma_channel_handle_t dma_chan, gdma_event_data_t *event_data, void *user_data)
{
    esp_rgb_panel_t *panel = (esp_rgb_panel_t*)user_data;
    dma_descriptor_t *desc = (dma_descriptor_t*)event_data->tx_eof_desc_addr;
    //Figure out which bounce buffer to write to.
    //Note: what we receive is the *last* descriptor of this bounce buffer.
    int bb=(desc==&panel->dma_nodes[panel->num_dma_nodes - 1])?1:0;
    return lcd_rgb_panel_fill_bounce_buffer(panel, panel->bounce_buffer[bb]);
}

//If we restart GDMA, this many pixels will already have been transfered to the
//LCD peripheral. Looks like that has 16 pixels of FIFO plus one holding register.
#define LCD_FIFO_SIZE_PX 17

static esp_err_t lcd_rgb_panel_create_trans_link(esp_rgb_panel_t *panel)
{
    esp_err_t ret = ESP_OK;
    if (panel->bounce_buffer_size_bytes == 0) {
        // Create DMA descriptors for main framebuffer:
        // chain DMA descriptors
        for (int i = 0; i < panel->num_dma_nodes; i++) {
            panel->dma_nodes[i].dw0.owner = DMA_DESCRIPTOR_BUFFER_OWNER_CPU;
            panel->dma_nodes[i].next = &panel->dma_nodes[i + 1];
        }
        // loop end back to start (note: this is needed as we restart the DMA transaction in the VBlank,
        // but it should already have LCD_FIFO_PIX bytes from the start of the buffer at that time)
        panel->dma_nodes[panel->num_dma_nodes - 1].next = &panel->dma_nodes[0];
        // mount the frame buffer to the DMA descriptors
        lcd_com_mount_dma_data(panel->dma_nodes, panel->fb, panel->fb_size);
    } else {
        //Create DMA descriptors for bounce buffers:
        // chain DMA descriptors
        for (int i = 0; i < panel->num_dma_nodes; i++) {
            panel->dma_nodes[i].dw0.owner = DMA_DESCRIPTOR_BUFFER_OWNER_CPU;
            panel->dma_nodes[i].next = &panel->dma_nodes[i + 1];
        }
        // loop end back to start
        panel->dma_nodes[panel->num_dma_nodes - 1].next = &panel->dma_nodes[0];
        // set eof on end of 1st and 2nd bounce buffer so we get an interrupt when they're fully sent
        panel->dma_nodes[(panel->num_dma_nodes/2) - 1].dw0.suc_eof=1;
        panel->dma_nodes[panel->num_dma_nodes - 1].dw0.suc_eof=1;
        // mount the bounce buffers to the DMA descriptors
        lcd_com_mount_dma_data(&panel->dma_nodes[0], panel->bounce_buffer[0], panel->bounce_buffer_size_bytes);
        lcd_com_mount_dma_data(&panel->dma_nodes[(panel->num_dma_nodes/2)], panel->bounce_buffer[1], panel->bounce_buffer_size_bytes);
    }
    //On restart, the data sent to the LCD peripheral needs to start 17 pixels after the FB start (the length of the
    //lcd fifo) so we use a special DMA node to restart the DMA transaction.
    memcpy(&panel->dma_restart_node, &panel->dma_nodes[0], sizeof(panel->dma_restart_node));
    int restart_skip_bytes=LCD_FIFO_SIZE_PX*sizeof(uint16_t);
    uint8_t *p=(uint8_t*)panel->dma_restart_node.buffer;
    panel->dma_restart_node.buffer=&p[restart_skip_bytes];
    panel->dma_restart_node.dw0.length-=restart_skip_bytes;
    panel->dma_restart_node.dw0.size-=restart_skip_bytes;

    // alloc DMA channel and connect to LCD peripheral
    gdma_channel_alloc_config_t dma_chan_config = {
        .direction = GDMA_CHANNEL_DIRECTION_TX,
    };
    ret = gdma_new_channel(&dma_chan_config, &panel->dma_chan);
    ESP_GOTO_ON_ERROR(ret, err, TAG, "alloc DMA channel failed");
    gdma_connect(panel->dma_chan, GDMA_MAKE_TRIGGER(GDMA_TRIG_PERIPH_LCD, 0));
    gdma_transfer_ability_t ability = {
        .psram_trans_align = panel->psram_trans_align,
        .sram_trans_align = panel->sram_trans_align,
    };
    gdma_set_transfer_ability(panel->dma_chan, &ability);
    if (panel->bounce_buffer_size_bytes != 0) {
        // register callback to re-fill bounce buffers once they're fully sent
        gdma_tx_event_callbacks_t cbs={0};
        cbs.on_trans_eof = lcd_rgb_panel_eof_handler;
        gdma_register_tx_event_callbacks(panel->dma_chan, &cbs, panel);
    }
    // the start of DMA should be prior to the start of LCD engine
    gdma_start(panel->dma_chan, (intptr_t)panel->dma_nodes);

err:
    return ret;
}

static IRAM_ATTR void lcd_rgb_panel_restart_transmission(esp_rgb_panel_t *panel)
{
    if (panel->bounce_buffer_size_bytes != 0) {
        //Catch de-synced framebuffer and reset if needed.
        if (panel->bounce_pos_px > panel->bounce_buffer_size_bytes) panel->bounce_pos_px=0;
        //Pre-fill bounce buffer 0, if the EOF ISR didn't do that already
        if (panel->bounce_pos_px < panel->bounce_buffer_size_bytes/2) {
            lcd_rgb_panel_fill_bounce_buffer(panel, panel->bounce_buffer[0]);
        }
    }

    gdma_reset(panel->dma_chan);
    gdma_start(panel->dma_chan, (intptr_t)&panel->dma_restart_node);

    if (panel->bounce_buffer_size_bytes != 0) {
        //Fill 2nd bounce buffer while 1st is being sent out, if needed.
        if (panel->bounce_pos_px < panel->bounce_buffer_size_bytes) {
            lcd_rgb_panel_fill_bounce_buffer(panel, panel->bounce_buffer[0]);
        }
    }
}

static void lcd_rgb_panel_start_transmission(esp_rgb_panel_t *rgb_panel)
{
    // reset FIFO of DMA and LCD, incase there remains old frame data
    gdma_reset(rgb_panel->dma_chan);
    lcd_ll_stop(rgb_panel->hal.dev);

    // check whether to update the PCLK frequency
    portENTER_CRITICAL_SAFE(&rgb_panel->spinlock);
    if (unlikely(rgb_panel->flags.need_update_pclk)) {
        rgb_panel->flags.need_update_pclk = false;
        rgb_panel->timings.pclk_hz = lcd_hal_cal_pclk_freq(&rgb_panel->hal, rgb_panel->src_clk_hz, rgb_panel->timings.pclk_hz);
    }
    portEXIT_CRITICAL_SAFE(&rgb_panel->spinlock);

    lcd_ll_fifo_reset(rgb_panel->hal.dev);

    //pre-fill bounce buffers if needed
    if (rgb_panel->bounce_buffer_size_bytes != 0) {
        rgb_panel->bounce_pos_px = 0;
        lcd_rgb_panel_fill_bounce_buffer(rgb_panel, rgb_panel->bounce_buffer[0]);
        lcd_rgb_panel_fill_bounce_buffer(rgb_panel, rgb_panel->bounce_buffer[1]);
    }

    gdma_start(rgb_panel->dma_chan, (intptr_t)rgb_panel->dma_nodes);
    // delay 1us is sufficient for DMA to pass data to LCD FIFO
    // in fact, this is only needed when LCD pixel clock is set too high
    esp_rom_delay_us(1);
    // start LCD engine
    lcd_ll_enable_auto_next_frame(rgb_panel->hal.dev, rgb_panel->flags.stream_mode);
    lcd_ll_start(rgb_panel->hal.dev);
}

IRAM_ATTR static void lcd_default_isr_handler(void *args)
{
    esp_rgb_panel_t *rgb_panel = (esp_rgb_panel_t *)args;
    bool need_yield = false;

    uint32_t intr_status = lcd_ll_get_interrupt_status(rgb_panel->hal.dev);
    lcd_ll_clear_interrupt_status(rgb_panel->hal.dev, intr_status);
    if (intr_status & LCD_LL_EVENT_VSYNC_END) {
        // call user registered callback
        if (rgb_panel->on_frame_trans_done) {
            if (rgb_panel->on_frame_trans_done(&rgb_panel->base, NULL, rgb_panel->user_ctx)) {
                need_yield = true;
            }
        }
        if (rgb_panel->flags.stream_mode) {
            // As described above, we reset the GDMA channel every VBlank to stop permanent
            // desyncs from happening.
            // Note that this fix can lead to single-frame desyncs itself, as in: if this interrupt
            // is late enough, the display will shift as the LCD controller already read out the
            // first data bytes, and resetting DMA will re-send those. However, the single-frame
            // desync this leads to is preferable to the permanent desync that could otherwise
            // happen. It's also not super-likely as this interrupt has the entirety of the VBlank
            // time to reset DMA.
            lcd_rgb_panel_restart_transmission(rgb_panel);
        }
    }

    if (need_yield) {
        portYIELD_FROM_ISR();
    }
}