From 2f35a81e0d9835896e41bb2ad76ccbad161e6695 Mon Sep 17 00:00:00 2001
From: Martin Stumpf <martin.stumpf@vected.de>
Date: Wed, 16 Oct 2024 16:42:15 +0200
Subject: [PATCH] display: add display_finalize_frame

Propagates the `lv_disp_flush_is_last` to the `display` subsystem.
Can be used to combine multiple `writes` to a single page-flip.

Signed-off-by: Martin Stumpf <martin.stumpf@vected.de>
---
 drivers/display/display_dummy.c  |  6 ++++++
 include/zephyr/drivers/display.h | 30 ++++++++++++++++++++++++++++++
 modules/lvgl/Kconfig             |  1 +
 modules/lvgl/lvgl_display.c      |  9 +++++++++
 modules/lvgl/lvgl_display_mono.c |  4 ++++
 5 files changed, 50 insertions(+)

diff --git a/drivers/display/display_dummy.c b/drivers/display/display_dummy.c
index 1a11ee2bf36d7ab..8016af9ff519c06 100644
--- a/drivers/display/display_dummy.c
+++ b/drivers/display/display_dummy.c
@@ -57,6 +57,11 @@ static int dummy_display_write(const struct device *dev, const uint16_t x,
 	return 0;
 }
 
+static int dummy_display_finalize_frame(const struct device *dev)
+{
+	return 0;
+}
+
 static int dummy_display_blanking_off(const struct device *dev)
 {
 	return 0;
@@ -110,6 +115,7 @@ static const struct display_driver_api dummy_display_api = {
 	.blanking_on = dummy_display_blanking_on,
 	.blanking_off = dummy_display_blanking_off,
 	.write = dummy_display_write,
+	.finalize_frame = dummy_display_finalize_frame,
 	.set_brightness = dummy_display_set_brightness,
 	.set_contrast = dummy_display_set_contrast,
 	.get_capabilities = dummy_display_get_capabilities,
diff --git a/include/zephyr/drivers/display.h b/include/zephyr/drivers/display.h
index 067d441d4551b4e..f0e074dd2cc5211 100644
--- a/include/zephyr/drivers/display.h
+++ b/include/zephyr/drivers/display.h
@@ -163,6 +163,13 @@ typedef int (*display_read_api)(const struct device *dev, const uint16_t x,
 				const struct display_buffer_descriptor *desc,
 				void *buf);
 
+/**
+ * @typedef display_finalize_frame_api
+ * @brief Callback API to indicate that all writes for the current frame are done
+ * See display_finalize_frame() for argument description
+ */
+typedef int (*display_finalize_frame_api)(const struct device *dev);
+
 /**
  * @typedef display_get_framebuffer_api
  * @brief Callback API to get framebuffer pointer
@@ -222,6 +229,7 @@ __subsystem struct display_driver_api {
 	display_blanking_off_api blanking_off;
 	display_write_api write;
 	display_read_api read;
+	display_finalize_frame_api finalize_frame;
 	display_get_framebuffer_api get_framebuffer;
 	display_set_brightness_api set_brightness;
 	display_set_contrast_api set_contrast;
@@ -279,6 +287,28 @@ static inline int display_read(const struct device *dev, const uint16_t x,
 	return api->read(dev, x, y, desc, buf);
 }
 
+/**
+ * @brief Indicates that all writes for the current frame are done
+ *
+ * Can be used to present all previous writes simultaneously, for
+ * double buffered or latched displays.
+ *
+ * @param dev Pointer to device structure
+ *
+ * @retval 0 on success else negative errno code.
+ */
+static inline int display_finalize_frame(const struct device *dev)
+{
+	struct display_driver_api *api = (struct display_driver_api *)dev->api;
+
+	if (api->finalize_frame == NULL) {
+		return -ENOSYS;
+	}
+
+	return api->finalize_frame(dev);
+}
+
+
 /**
  * @brief Get pointer to framebuffer for direct access
  *
diff --git a/modules/lvgl/Kconfig b/modules/lvgl/Kconfig
index 932df9e55d979bf..a31015cc30beb62 100644
--- a/modules/lvgl/Kconfig
+++ b/modules/lvgl/Kconfig
@@ -102,6 +102,7 @@ config LV_Z_FLUSH_THREAD_STACK_SIZE
 	default 1024
 	help
 	  Stack size for LVGL flush thread, which will call display_write
+	  and display_finalize_frame
 
 config LV_Z_FLUSH_THREAD_PRIO
 	int "LVGL flush thread priority"
diff --git a/modules/lvgl/lvgl_display.c b/modules/lvgl/lvgl_display.c
index 604cd0078d806f9..e52511805bef77d 100644
--- a/modules/lvgl/lvgl_display.c
+++ b/modules/lvgl/lvgl_display.c
@@ -28,6 +28,10 @@ void lvgl_flush_thread_entry(void *arg1, void *arg2, void *arg3)
 		display_write(data->display_dev, flush.x, flush.y, &flush.desc,
 			      flush.buf);
 
+		if (lv_disp_flush_is_last(flush.disp_drv)) {
+			display_finalize_frame(data->display_dev);
+		}
+
 		lv_disp_flush_ready(flush.disp_drv);
 		k_sem_give(&flush_complete);
 	}
@@ -134,6 +138,11 @@ void lvgl_flush_display(struct lvgl_display_flush *request)
 
 	display_write(data->display_dev, request->x, request->y,
 		      &request->desc, request->buf);
+
+	if (lv_disp_flush_is_last(request->disp_drv)) {
+		display_finalize_frame(data->display_dev);
+	}
+
 	lv_disp_flush_ready(request->disp_drv);
 #endif
 }
diff --git a/modules/lvgl/lvgl_display_mono.c b/modules/lvgl/lvgl_display_mono.c
index 07f84b7d19efc7a..b515c586b479407 100644
--- a/modules/lvgl/lvgl_display_mono.c
+++ b/modules/lvgl/lvgl_display_mono.c
@@ -38,6 +38,10 @@ void lvgl_flush_cb_mono(lv_disp_drv_t *disp_drv, const lv_area_t *area, lv_color
 		display_write(display_dev, area->x1, area->y1, &desc, (void *)color_p);
 	}
 
+	if (is_last) {
+		display_finalize_frame(display_dev);
+	}
+
 	if (is_epd && is_last && data->blanking_on) {
 		/*
 		 * The entire screen has now been rendered. Update the