cmd: Add pause command

This command is being introduced with the goal of allowing user-friendly
"generic use case" U-Boot builds to pause until user input under some
situations.

The main use case would be when a boot failure happens, to pause until
the user has had time to acknowledge the current state.

Tested using:

    make && ./u-boot -v -T -c 'ut lib lib_test_hush_pause'

Signed-off-by: Samuel Dionne-Riel <samuel@dionne-riel.com>
Cc: Simon Glass <sjg@chromium.org>

cmd/Kconfig

@@ -1971,6 +1971,12 @@ config CMD_GETTIME
 	  milliseconds. See also the 'bootstage' command which provides more
 	  flexibility for boot timing.
 
+config CMD_PAUSE
+	bool "pause command"
+	help
+	  Delay execution waiting for any user input.
+	  Useful to allow the user to read a failure log.
+
 config CMD_RNG
 	bool "rng command"
 	depends on DM_RNG

cmd/Makefile

@@ -102,6 +102,7 @@ obj-$(CONFIG_CMD_MFSL) += mfsl.o
 obj-$(CONFIG_CMD_MII) += mii.o
 obj-$(CONFIG_CMD_MISC) += misc.o
 obj-$(CONFIG_CMD_MDIO) += mdio.o
+obj-$(CONFIG_CMD_PAUSE) += pause.o
 obj-$(CONFIG_CMD_SLEEP) += sleep.o
 obj-$(CONFIG_CMD_MMC) += mmc.o
 obj-$(CONFIG_CMD_OPTEE_RPMB) += optee_rpmb.o

cmd/pause.c

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2021
+ * Samuel Dionne-Riel <samuel@dionne-riel.com>
+ */
+
+#include <command.h>
+#include <stdio.h>
+
+static int do_pause(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
+{
+	char *message = "Press any key to continue...";
+
+	if (argc == 2)
+		message = argv[1];
+
+	/* No newline, so it sticks to the bottom of the screen */
+	printf("%s", message);
+
+	/* Wait on "any" key... */
+	(void) getchar();
+
+	/* Since there was no newline, we need it now */
+	printf("\n");
+
+	return CMD_RET_SUCCESS;
+}
+
+U_BOOT_CMD(pause, 2, 1, do_pause,
+	"delay until user input",
+	"[prompt] - Wait until users presses any key. [prompt] can be used to customize the message.\n"
+);