[RPI][SPLASH] patch u-boot to display splash bmp from sd

- display the splash screen
- enable the splaspos environment variable to configure positioning of the splash image
- enable the splashsource library, which allows to load the logo image from a custom source (see README.splashprepare)
- quiet console messages (see README.silent), which would otherwise overlap with the logo image
- enable CONFIG_SILENT_U_BOOT_ONLY to prevent U-boot from adding "quiet" to the bootargs, which would also hide the kernel logo
- NOTE: in the future we might want to direct the console output to the GPIO serial instead of silencing it entirely

recipes-bsp/u-boot/files/0001-RPI-SPLASH-enable-splash-and-quiet-console.patch

+From a427f9b80da8ed19a3ba22b8f427c6eb659cdca8 Mon Sep 17 00:00:00 2001
+From: Alessandro Pecugi <alessandro.pecugi@seco.com>
+Date: Wed, 13 Sep 2023 16:00:42 +0200
+Subject: [PATCH] [RPI][SPLASH] enable splash, splashsource and quiet console
+
+- display the splash screen
+- enable the splaspos environment variable to configure positioning of the splash image
+- enable the splashsource library, which allows to load the logo image from a custom source (see README.splashprepare)
+- quiet console messages (see README.silent), which would otherwise overlap with the logo image
+- enable CONFIG_SILENT_U_BOOT_ONLY to prevent U-boot from adding "quiet" to the bootargs, which would also hide the kernel logo
+- NOTE: in the future we might want to direct the console output to the GPIO serial instead of silencing it entirely
+---
+ configs/rpi_arm64_defconfig | 8 ++++++++
+ include/configs/rpi.h       | 6 +++++-
+ 2 files changed, 13 insertions(+), 1 deletion(-)
+
+diff --git a/configs/rpi_arm64_defconfig b/configs/rpi_arm64_defconfig
+index 06ae3e93b2..1534602c7d 100644
+--- a/configs/rpi_arm64_defconfig
++++ b/configs/rpi_arm64_defconfig
+@@ -53,3 +53,11 @@ CONFIG_SYS_WHITE_ON_BLACK=y
+ CONFIG_CONSOLE_SCROLL_LINES=10
+ CONFIG_PHYS_TO_BUS=y
+ CONFIG_OF_LIBFDT_OVERLAY=y
++
++CONFIG_SPLASH_SCREEN=y
++CONFIG_CMD_BMP=y
++CONFIG_SPLASH_SCREEN_ALIGN=y
++CONFIG_SPLASH_SOURCE=y
++CONFIG_BMP_24BPP=y
++CONFIG_SILENT_CONSOLE=y
++CONFIG_SILENT_U_BOOT_ONLY=y
+diff --git a/include/configs/rpi.h b/include/configs/rpi.h
+index 4c5c1ac31f..734f6e8ab6 100644
+--- a/include/configs/rpi.h
++++ b/include/configs/rpi.h
+@@ -174,7 +174,11 @@
+ 	ENV_DEVICE_SETTINGS \
+ 	ENV_DFU_SETTINGS \
+ 	ENV_MEM_LAYOUT_SETTINGS \
+-	BOOTENV
++	BOOTENV \
++	"splashpos=m,m\0" \
++	"splashimage=" __stringify(CONFIG_SYS_LOAD_ADDR) "\0" \
++	"splashsource=mmc_fs\0" \
++	"silent=1\0"        // quiet messages on the console so that they don't cover the splash screen (see README.silent)
+ 
+ 
+ #endif
+-- 
+2.34.1
+

recipes-bsp/u-boot/u-boot_2022.01.bbappend

+FILESEXTRAPATHS:prepend := "${THISDIR}/files:"
+SRC_URI += "file://0001-RPI-SPLASH-enable-splash-and-quiet-console.patch"
\ No newline at end of file