- improve video sync performance with background syncing (cyclic)

- fix dropping characters when pasting commands over the UART
  - enable background syncing by default for boards using VIDEO
  - make sandbox video more responsive
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Merge tag 'video-20240731' of https://source.denx.de/u-boot/custodians/u-boot-video

 - improve video sync performance with background syncing (cyclic)
 - fix dropping characters when pasting commands over the UART
 - enable background syncing by default for boards using VIDEO
 - make sandbox video more responsive

common/Kconfig

@@ -626,8 +626,17 @@ config CYCLIC
 
 if CYCLIC
 
+config SPL_CYCLIC
+	bool "General-purpose cyclic execution mechanism (SPL)"
+	help
+	  This enables a general-purpose cyclic execution infrastructure in SPL,
+	  to allow "small" (run-time wise) functions to be executed at
+	  a specified frequency. Things like LED blinking or watchdog
+	  triggering are examples for such tasks.
+
 config CYCLIC_MAX_CPU_TIME_US
 	int "Sets the max allowed time for a cyclic function in us"
+	default 100000 if SANDBOX  # sandbox video is quite slow
 	default 5000
 	help
 	  The max allowed time for a cyclic function in us. If a functions

common/Makefile

@@ -79,7 +79,7 @@ obj-$(CONFIG_CROS_EC) += cros_ec.o
 obj-y += dlmalloc.o
 obj-$(CONFIG_$(SPL_TPL_)SYS_MALLOC_F) += malloc_simple.o
 
-obj-$(CONFIG_CYCLIC) += cyclic.o
+obj-$(CONFIG_$(SPL_TPL_)CYCLIC) += cyclic.o
 obj-$(CONFIG_$(SPL_TPL_)EVENT) += event.o
 
 obj-$(CONFIG_$(SPL_TPL_)HASH) += hash.o

drivers/serial/sandbox.c

@@ -138,8 +138,6 @@ static int sandbox_serial_pending(struct udevice *dev, bool input)
 		return 0;
 
 	os_usleep(100);
-	if (IS_ENABLED(CONFIG_VIDEO) && !IS_ENABLED(CONFIG_SPL_BUILD))
-		video_sync_all();
 	avail = membuff_putraw(&priv->buf, 100, false, &data);
 	if (!avail)
 		return 1;	/* buffer full */

drivers/video/Kconfig

@@ -7,6 +7,7 @@ menu "Graphics support"
 config VIDEO
 	bool "Enable driver model support for LCD/video"
 	depends on DM
+	imply CYCLIC
 	help
 	  This enables driver model for LCD and video devices. These support
 	  a bitmap display of various sizes and depths which can be drawn on
@@ -14,6 +15,11 @@ config VIDEO
 	  option compiles in the video uclass and routes all LCD/video access
 	  through this.
 
+	  If CYCLIC is enabled (which it is by default), the cyclic subsystem
+	  is used to flush pending output to the display periodically, rather
+	  than this happening with every chunk of output. This allows for more
+	  efficient operation and faster display output.
+
 if VIDEO
 
 config VIDEO_FONT_4X6
@@ -232,6 +238,35 @@ config NO_FB_CLEAR
 	  loads takes over the screen.  This, for example, can be used to
 	  keep splash image on screen until grub graphical boot menu starts.
 
+config VIDEO_SYNC_MS
+	int "Video-sync period in milliseconds for foreground processing"
+	default 300 if SANDBOX
+	default 100
+	help
+	  This sets the requested, maximum time before a video sync will take
+	  place, in milliseconds. Note that the time between video syncs
+	  may be longer than this, since syncs only happen when the video system
+	  is used, e.g. by outputting a character to the console.
+
+	  It may also be shorter, since the video uclass will automatically
+	  force a sync in certain situations.
+
+	  Many video-output systems require a sync operation before any output
+	  is visible. This may flush the CPU cache or perhaps copy the
+	  display contents to a hardware framebuffer. Without this, change to
+	  the video may never be displayed.
+
+config VIDEO_SYNC_CYCLIC_MS
+	int "Video-sync period in milliseconds for cyclic processing"
+	depends on CYCLIC
+	default 100 if SANDBOX
+	default 10
+	help
+	  This sets the frequency of cyclic video syncs. The cyclic system is
+	  used to ensure that when U-Boot is idle, it syncs the video. This
+	  improves the responsiveness of the command line to new characters
+	  being entered.
+
 config PANEL
 	bool "Enable panel uclass support"
 	default y

drivers/video/video-uclass.c

@@ -8,6 +8,7 @@
 #include <bloblist.h>
 #include <console.h>
 #include <cpu_func.h>
+#include <cyclic.h>
 #include <dm.h>
 #include <log.h>
 #include <malloc.h>
@@ -52,6 +53,8 @@
  */
 DECLARE_GLOBAL_DATA_PTR;
 
+struct cyclic_info;
+
 /**
  * struct video_uc_priv - Information for the video uclass
  *
@@ -60,9 +63,12 @@ DECLARE_GLOBAL_DATA_PTR;
  *	available address to use for a device's framebuffer. It starts at
  *	gd->video_top and works downwards, running out of space when it hits
  *	gd->video_bottom.
+ * @cyc: handle for cyclic-execution function, or NULL if none
  */
 struct video_uc_priv {
 	ulong video_ptr;
+	bool cyc_active;
+	struct cyclic_info cyc;
 };
 
 /** struct vid_rgb - Describes a video colour */
@@ -349,6 +355,7 @@ void video_set_default_colors(struct udevice *dev, bool invert)
 /* Flush video activity to the caches */
 int video_sync(struct udevice *vid, bool force)
 {
+	struct video_priv *priv = dev_get_uclass_priv(vid);
 	struct video_ops *ops = video_get_ops(vid);
 	int ret;
 
@@ -358,28 +365,26 @@ int video_sync(struct udevice *vid, bool force)
 			return ret;
 	}
 
+	if (CONFIG_IS_ENABLED(CYCLIC) && !force &&
+	    get_timer(priv->last_sync) < CONFIG_VIDEO_SYNC_MS)
+		return 0;
+
 	/*
 	 * flush_dcache_range() is declared in common.h but it seems that some
 	 * architectures do not actually implement it. Is there a way to find
 	 * out whether it exists? For now, ARM is safe.
 	 */
 #if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)
-	struct video_priv *priv = dev_get_uclass_priv(vid);
-
 	if (priv->flush_dcache) {
 		flush_dcache_range((ulong)priv->fb,
 				   ALIGN((ulong)priv->fb + priv->fb_size,
 					 CONFIG_SYS_CACHELINE_SIZE));
 	}
 #elif defined(CONFIG_VIDEO_SANDBOX_SDL)
-	struct video_priv *priv = dev_get_uclass_priv(vid);
+	sandbox_sdl_sync(priv->fb);
-	static ulong last_sync;
-
-	if (force || get_timer(last_sync) > 100) {
-		sandbox_sdl_sync(priv->fb);
-		last_sync = get_timer(0);
-	}
 #endif
+	priv->last_sync = get_timer(0);
+
 	return 0;
 }
 
@@ -528,10 +533,16 @@ int video_default_font_height(struct udevice *dev)
 	return vc_priv->y_charsize;
 }
 
+static void video_idle(struct cyclic_info *cyc)
+{
+	video_sync_all();
+}
+
 /* Set up the display ready for use */
 static int video_post_probe(struct udevice *dev)
 {
 	struct video_uc_plat *plat = dev_get_uclass_plat(dev);
+	struct video_uc_priv *uc_priv = uclass_get_priv(dev->uclass);
 	struct video_priv *priv = dev_get_uclass_priv(dev);
 	char name[30], drv[15], *str;
 	const char *drv_name = drv;
@@ -622,6 +633,16 @@ static int video_post_probe(struct udevice *dev)
 		}
 	}
 
+	/* register cyclic as soon as the first video device is probed */
+	if (CONFIG_IS_ENABLED(CYCLIC) && (gd->flags && GD_FLG_RELOC) &&
+	    !uc_priv->cyc_active) {
+		uint ms = CONFIG_IF_ENABLED_INT(CYCLIC, VIDEO_SYNC_CYCLIC_MS);
+
+		cyclic_register(&uc_priv->cyc, video_idle, ms * 1000,
+				"video_init");
+		uc_priv->cyc_active = true;
+	}
+
 	return 0;
 };
 
@@ -661,6 +682,18 @@ static int video_post_bind(struct udevice *dev)
 	return 0;
 }
 
+__maybe_unused static int video_destroy(struct uclass *uc)
+{
+	struct video_uc_priv *uc_priv = uclass_get_priv(uc);
+
+	if (uc_priv->cyc_active) {
+		cyclic_unregister(&uc_priv->cyc);
+		uc_priv->cyc_active = false;
+	}
+
+	return 0;
+}
+
 UCLASS_DRIVER(video) = {
 	.id		= UCLASS_VIDEO,
 	.name		= "video",
@@ -670,4 +703,5 @@ UCLASS_DRIVER(video) = {
 	.priv_auto	= sizeof(struct video_uc_priv),
 	.per_device_auto	= sizeof(struct video_priv),
 	.per_device_plat_auto	= sizeof(struct video_uc_plat),
+	CONFIG_IS_ENABLED(CYCLIC, (.destroy = video_destroy, ))
 };

drivers/watchdog/Kconfig

@@ -4,6 +4,7 @@ config WATCHDOG
 	bool "Enable U-Boot watchdog reset"
 	depends on !HW_WATCHDOG
 	select CYCLIC
+	imply SPL_CYCLIC if SPL
 	help
 	  This option enables U-Boot watchdog support where U-Boot is using
 	  watchdog_reset function to service watchdog device in U-Boot. Enable
@@ -408,6 +409,7 @@ config WDT_ARM_SMC
 config SPL_WDT
 	bool "Enable driver model for watchdog timer drivers in SPL"
 	depends on SPL_DM
+	select SPL_CYCLIC if CYCLIC
 	help
 	  Enable driver model for watchdog timer in SPL.
 	  This is similar to CONFIG_WDT in U-Boot.

include/asm-generic/global_data.h

@@ -481,7 +481,7 @@ struct global_data {
 	 */
 	struct event_state event_state;
 #endif
-#ifdef CONFIG_CYCLIC
+#if CONFIG_IS_ENABLED(CYCLIC)
 	/**
 	 * @cyclic_list: list of registered cyclic functions
 	 */

include/cyclic.h

@@ -46,7 +46,8 @@ struct cyclic_info {
 /** Function type for cyclic functions */
 typedef void (*cyclic_func_t)(struct cyclic_info *c);
 
-#if defined(CONFIG_CYCLIC)
+#if CONFIG_IS_ENABLED(CYCLIC)
+
 /**
  * cyclic_register - Register a new cyclic function
  *
@@ -123,6 +124,6 @@ static inline int cyclic_unregister_all(void)
 {
 	return 0;
 }
-#endif
+#endif /* CYCLIC */
 
 #endif

include/video.h

@@ -97,6 +97,7 @@ enum video_format {
  *		the LCD is updated
  * @fg_col_idx:	Foreground color code (bit 3 = bold, bit 0-2 = color)
  * @bg_col_idx:	Background color code (bit 3 = bold, bit 0-2 = color)
+ * @last_sync:	Monotonic time of last video sync
  */
 struct video_priv {
 	/* Things set up by the driver: */
@@ -121,6 +122,7 @@ struct video_priv {
 	bool flush_dcache;
 	u8 fg_col_idx;
 	u8 bg_col_idx;
+	ulong last_sync;
 };
 
 /**