lcd: split gpio check for de and hv mode

components/esp_lcd/include/esp_lcd_panel_rgb.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -64,7 +64,7 @@ typedef struct {
         unsigned int hsync_idle_low: 1;  /*!< The hsync signal is low in IDLE state */
         unsigned int vsync_idle_low: 1;  /*!< The vsync signal is low in IDLE state */
         unsigned int de_idle_high: 1;    /*!< The de signal is high in IDLE state */
-        unsigned int pclk_active_neg: 1; /*!< The display will write data lines when there's a falling edge on PCLK */
+        unsigned int pclk_active_neg: 1; /*!< Whether the display data is clocked out at the falling edge of PCLK */
         unsigned int pclk_idle_high: 1;  /*!< The PCLK stays at high level in IDLE phase */
     } flags;
 } esp_lcd_rgb_timing_t;

components/esp_lcd/src/esp_lcd_rgb_panel.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -379,8 +379,11 @@ static esp_err_t lcd_rgb_panel_configure_gpio(esp_rgb_panel_t *panel, const esp_
 {
     int panel_id = panel->panel_id;
     // check validation of GPIO number
-    bool valid_gpio = (panel_config->hsync_gpio_num >= 0) && (panel_config->vsync_gpio_num >= 0) &&
+    bool valid_gpio = (panel_config->pclk_gpio_num >= 0);
-                      (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);
     }
@@ -394,14 +397,18 @@ static esp_err_t lcd_rgb_panel_configure_gpio(esp_rgb_panel_t *panel, const esp_
         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,