feat(linux): Update boot time guide

paresh-bhagat · paresh-bhagat · commit c2b565e6ae8c · 2026-04-28T14:02:21.000+05:30
- Fix RST syntax, formatting issues, links.
- Update steps for early display testing and initramfs build.
- Improve filesystem setup documentation.
- Update boot time values.

Signed-off-by: Paresh Bhagat &lt;p-bhagat@ti.com&gt;
diff --git a/source/linux/How_to_Guides/Target/How_to_boot_quickly.rst b/source/linux/How_to_Guides/Target/How_to_boot_quickly.rst
@@ -26,7 +26,7 @@ The objectives of this document are as follows:
 
 Software environment
 ^^^^^^^^^^^^^^^^^^^^
-This guide uses 10.0 Processor SDK as reference.
+This guide uses Processor SDK and MCU+SDK as reference.
 
 .. ifconfig:: CONFIG_part_variant in ('AM62X')
 
@@ -135,7 +135,7 @@ Reducing bootloader time
 
 .. ifconfig:: CONFIG_part_variant in ('AM62PX')
 
-    You can track current performance numbers here: `AM62PX <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/11_01_01_08/exports/docs/api_guide_am62px/DATASHEET_AM62PX_EVM.html#autotoc_md119>`_
+    You can track current performance numbers here: `AM62PX <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/12_00_00_27/exports/docs/api_guide_am62px/DATASHEET_AM62PX_EVM.html#autotoc_md119>`_
 
 
 - Flashing binaries:
@@ -158,7 +158,7 @@ Reducing bootloader time
 
     .. ifconfig:: CONFIG_part_variant in ('AM62PX')
 
-        - `UART flashing tool AM62PX <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/11_01_01_08/exports/docs/api_guide_am62px/TOOLS_FLASH.html>`_
+        - `UART flashing tool AM62PX <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/12_00_00_27/exports/docs/api_guide_am62px/TOOLS_FLASH.html>`_
 
         - U-Boot eMMC flashing tool AM62PX: :ref:`u-boot-build-guide-environment-k3`
 
@@ -176,7 +176,7 @@ Secondary Boot Loader (SBL)
 
 .. ifconfig:: CONFIG_part_variant in ('AM62PX')
 
-    The following section will reference `AM62PX MCU+ SDK's SBL examples <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/11_01_01_08/exports/docs/api_guide_am62px/EXAMPLES_DRIVERS_SBL.html>`_.
+    The following section will reference `AM62PX MCU+ SDK's SBL examples <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/12_00_00_27/exports/docs/api_guide_am62px/EXAMPLES_DRIVERS_SBL.html>`_.
 
 .. ifconfig:: CONFIG_part_variant in ('AM62X')
 
@@ -188,7 +188,7 @@ Secondary Boot Loader (SBL)
 
 .. ifconfig:: CONFIG_part_variant in ('AM62PX')
 
-    - `AM62PX Falcon Mode <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/11_01_01_08/exports/docs/api_guide_am62px/TOOLS_BOOT.html#LINUX_APPIMAGE_GEN_TOOL>`_
+    - `AM62PX Falcon Mode <https://software-dl.ti.com/mcu-plus-sdk/esd/AM62PX/12_00_00_27/exports/docs/api_guide_am62px/TOOLS_BOOT.html#LINUX_APPIMAGE_GEN_TOOL>`_
 
 - Removing unnecessary prints
 
@@ -305,7 +305,85 @@ Reducing Linux kernel boot time
 Reducing userspace boot time
 ----------------------------
 
-It is recommended to use a tiny intermediate filesystem that can be used to run applications early with minimal configuration and then mount into a filesystem with full functionality. For this purpose, the installer packages a filesystem: :file:`<PSDK_PATH>/filesystem/<machine>/tisdk-tiny-initramfs-am62xx-evm.cpio` that can be used as an initramfs.
+Use a tiny filesystem to run applications early with minimal configuration. You can build a custom minimal tisdk-tiny-initramfs using Yocto.
+
+Building custom tiny initramfs
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. note::
+
+    For detailed instructions on setting up the Yocto build environment, see :ref:`building-the-sdk-with-yocto`.
+
+To build the sysvinit based :file:`tisdk-tiny-initramfs-am62xx-evm.cpio` using Yocto, follow these steps:
+
+1. Clone and setup the Yocto environment:
+
+    .. code-block:: console
+
+        $ git clone https://git.ti.com/git/arago-project/oe-layersetup.git tisdk
+        $ cd tisdk
+        $ ./oe-layertool-setup.sh -f configs/processor-sdk/<oeconfig-file>
+
+2. Configure local.conf to use sysvinit instead of systemd:
+
+    .. code-block:: console
+
+        $ cd build
+        $ echo 'DISTRO_FEATURES:append = " sysvinit"' >> conf/local.conf
+        $ echo 'DISTRO_FEATURES:remove = "systemd"' >> conf/local.conf
+        $ echo 'ARAGO_SYSVINIT = "1"' >> conf/local.conf
+
+3. Apply recipe changes in meta-tisdk:
+
+    .. code-block:: console
+
+        $ cd ../sources/meta-tisdk
+
+    Apply the following diff to :file:`meta-ti-foundational/recipes-core/images/tisdk-tiny-initramfs.bb`
+
+    .. code-block:: diff
+
+        diff --git a/meta-ti-foundational/recipes-core/images/tisdk-tiny-initramfs.bb b/meta-ti-foundational/recipes-core/images/tisdk-tiny-initramfs.bb
+        index 232b734..a76d5f6 100644
+        --- a/meta-ti-foundational/recipes-core/images/tisdk-tiny-initramfs.bb
+        +++ b/meta-ti-foundational/recipes-core/images/tisdk-tiny-initramfs.bb
+        @@ -16,17 +16,6 @@ PACKAGE_INSTALL = " \
+             base-files \
+             base-passwd \
+             busybox \
+        -    netbase \
+        -    shadow-base \
+        -    update-alternatives-opkg \
+        -    parted \
+        -    util-linux \
+        -    e2fsprogs \
+        -    dosfstools \
+        -    mmc-utils \
+        -    tar \
+        -    gzip \
+        -    xz \
+        -    wget \
+        -    dropbear \
+        +    sysvinit \
+        +    initscripts \
+         "
+
+4. Setup build environment and build the custom initramfs:
+
+    .. code-block:: console
+
+        $ cd ../../build
+        $ . conf/setenv
+        $ MACHINE=am62xx-evm bitbake -k tisdk-tiny-initramfs
+
+.. note::
+
+    Since this is only a ramfs image, the MACHINE value does not significantly matter here.
+
+The built cpio file will be available in the deploy-ti directory: :file:`deploy-ti/images/<machine>/tisdk-tiny-initramfs-<machine>.cpio` and you can use it as described in the following sections.
+
+Optimizing the Filesystem
+^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 In order to package the filesystem as initramfs into the kernel, follow these steps:
 
@@ -317,16 +395,15 @@ In order to package the filesystem as initramfs into the kernel, follow these st
         $ cd output
         $ cpio -idv < tisdk-tiny-initramfs-am62xx-evm.cpio
 
-
 2. Edit the kernel config:
 
-    .config:
+    Edit .config file directly:
 
     .. code-block:: kconfig
 
         CONFIG_INITRAMFS_SOURCE="/path/to/filesystem"
 
-    or using :code:`menuconfig`:
+    or using :code:`menuconfig` and generate new .config:
 
     .. code-block:: kconfig
 
@@ -335,7 +412,9 @@ In order to package the filesystem as initramfs into the kernel, follow these st
         General setup ->
             Initial RAM filesystem and RAM disk (initramfs/initrd) support ->
                 Initramfs source file(s)
-                    /path/to/filesystem
+                    /path/to/filesystem or cpio file
+
+    Both cpio or filesystem path can be passed to "Initramfs source file". If providing a filesystem path directly, ensure required files and folders are executable. example :file:`/sbin/init` or :file:`/usr/bin/modetest`.
 
 3. Rebuild the kernel
 
@@ -355,9 +434,9 @@ The time taken to boot filesystem is measured from Process ID 1(PID1) to login p
 
         host$ rm <filesystem>/etc/rc5.d/*
         host$ cd <filesystem>/etc/rcS.d
-        host$ rm S02banner.sh S04udev S05checkroot.sh S06modutils.sh S07bootlogd S29read-only-rootfs-hook.sh S36bootmisc.sh S37populate-volatile.sh S38dmesg.sh S38urandom
+        host$ rm S02banner.sh S05checkroot.sh S07bootlogd S29read-only-rootfs-hook.sh S36bootmisc.sh S37populate-volatile.sh S38dmesg.sh S38urandom
 
-    This shaves off 1.536s from filesystem boot time. udev alone takes up 1.152s.
+    This shaves off 1.536s from filesystem boot time.
 
 - Remove package manager, console logo and add /dev/null in the filesystem
 
@@ -370,6 +449,63 @@ The time taken to boot filesystem is measured from Process ID 1(PID1) to login p
 
     This removes 52ms from the boot up time.
 
+- Custom Init Script for Maximum Boot Speed
+
+    For applications requiring fastest boot time, you can replace the default init system with a custom init script. This approach bypasses sysvinit entirely and provides direct access to the shell while running essential applications in the background. Use this approach if you don't need system services and prefer maximum boot speed over functionality.
+
+    Remove the existing :file:`/sbin/init` and create a custom :file:`/sbin/init` script with the following commands:
+
+    .. code-block:: sh
+
+        #!/bin/sh
+
+        mount -t proc none /proc
+        mount -t sysfs none /sys
+        mount -t devtmpfs dev /dev
+
+        # Uncomment to run modetest in the background
+        # 42 - connector ID
+        # 40 - CRTC ID
+        # 1920x1200 - resolution of panel
+        #(modetest -M tidss -s 42@40:1920x1200 0<&- 2>/tmp/output.log) &
+
+        # For sysvinit based flow
+        # Use either sysvinit or direct shell approach
+        # exec /sbin/init.sysvinit $*
+
+        # Shell - restarts automatically when exited
+        while true; do
+            /bin/sh </dev/console >/dev/console 2>&1
+        done
+
+    Make the script executable:
+
+    .. code-block:: console
+
+        host$ chmod +x <filesystem>/sbin/init
+
+    **Considerations:**
+
+    - No system services or proper init system functionality.
+    - Job control is limited (warning message: "can't access tty; job control turned off").
+    - The shell warning message is harmless and indicates that advanced terminal features are disabled.
+
+- Create symlink from init to sbin/init if it does not exist:
+
+    .. code-block:: console
+
+        host$ cd <filesystem>
+        host$ ln -sf /sbin/init init
+
+- Convert file system to cpio file.
+
+    .. code-block:: console
+
+       host$ cd <filesystem>
+       host$ find . | sort | cpio --reproducible -o -H newc -R root:root > ../tisdk-tiny-initramfs-new.cpio
+
+    Pass the new cpio file during kernel build.
+
 Measurements
 ------------
 
@@ -603,10 +739,10 @@ To measure the instance when the filesystem starts, navigate to :file:`init/main
 
     .. code-block:: console
 
-        [2025-12-09 14:29:28.387] NOTICE:  BL31: v2.13.0(release):v2.13.0-259-ge0c4d3903
-        [2025-12-09 14:29:28.387] NOTICE:  BL31: Built : 06:45:06, Dec  7 2025
-        [2025-12-09 14:29:29.107]
-        [2025-12-09 14:29:29.107] am62xx-evm login:
+        [2026-04-28 08:17:15.247] NOTICE:  BL31: v2.14.0(release):sandbox/v2.14-472-g76500ceae
+        [2026-04-28 08:17:15.247] NOTICE:  BL31: Built : 21:08:02, Apr 15 2026
+        [2026-04-28 08:17:15.807] /bin/sh: can't access tty; job control turned off
+        [2026-04-28 08:17:15.807] ~ #
 
     +-----------------+-----------+
     |      Stage      | Time (ms) |
@@ -615,66 +751,101 @@ To measure the instance when the filesystem starts, navigate to :file:`init/main
     +-----------------+-----------+
     |       ROM       |     31    |
     +-----------------+-----------+
-    |       SBL       |    200    |
+    |       SBL       |    214    |
     +-----------------+-----------+
-    |  Linux Kernel   |    549    |
+    |  Linux Kernel   |    523    |
     +-----------------+-----------+
-    |     Tiny FS     |    171    |
+    |     Tiny FS     |     37    |
     +-----------------+-----------+
-    |      Total      |    966    |
+    |      Total      |    820    |
     +-----------------+-----------+
 
-Bootloader loads HSM binary (9KB), MCU/DSP image (50KB) and Kernel+FS image (22MB) in the above measurements
+Boot loader loads HSM binary (9KB), MCU/DSP image (56KB) and Kernel+FS image (18MB) in the above measurements
 
 .. note::
 
    Filesytem time is measured using minicom time stamp. ( Boot Time via minicom - Kernel time by GPIO = Filesystem Time )
 
-Additional notes
-----------------
+Additional steps to test early display
+--------------------------------------
 
 .. ifconfig:: CONFIG_part_variant in ('AM62X', 'AM62PX')
 
     .. note::
 
         Ensure that you are not affecting your host computer when making the changes detailed below.
-        For early display with OLDI panel, disable bridge-hdmi or sii9022 node in device tree.
-        Also use fdtoverlay command to modify dtb file (base tree) with dtbo overlay for OLDI panel.
 
-    - This statically compiled :download:`modetest </files/modetest>` can be added to the filesystem to test out display at boot on an OLDI panel.
+    - For early display with OLDI panel, disable bridge-hdmi or sii9022 node in device tree.
+
+        .. code-block:: diff
+
+           diff --git a/arch/arm64/boot/dts/ti/k3-am62p5-sk.dts b/arch/arm64/boot/dts/ti/k3-am62p5-sk.dts
+           index e40abe7afe45..70153e592600 100644
+           --- a/arch/arm64/boot/dts/ti/k3-am62p5-sk.dts
+           +++ b/arch/arm64/boot/dts/ti/k3-am62p5-sk.dts
+           @@ -589,6 +589,7 @@ sii9022: bridge-hdmi@3b {
+                           interrupts = <16 IRQ_TYPE_EDGE_FALLING>;
+                           #sound-dai-cells = <0>;
+                           sil,i2s-data-lanes = < 0 >;
+           +               status = "disabled";
+
+    - Use fdtoverlay command to modify dtb file (base tree) with dtbo overlay for OLDI panel.
+
+        .. code-block:: console
+
+           host$ fdtoverlay -v -i k3-am62p5-sk.dtb -o merged.dtb k3-am62p5-sk-microtips-mf101hie-panel.dtbo
 
-        - `init` is a symbolic link to /sbin/init. Remove the file sbin/init
+        Later rename merged.dtb to k3-am62p5-sk.dtb when generating linux.falcon.appimage.hs_fs.
 
-            .. code-block:: console
+    - Add statically compiled :download:`modetest </files/modetest>` to filesystem to test out display at boot on an OLDI panel.
 
-                rm <filesystem>/sbin/init
+        .. code-block:: console
+
+           host$ cd <filesystem>
+           host$ cp ~/Downloads/modetest <filesystem>/usr/bin
+           host$ chmod +x modetest
+
+    - In the new :file:`sbin/init` created earlier, uncomment modetest.
+
+        .. code-block:: sh
 
-        - Create a new sbin/init and add the following.
+           #!/bin/sh
 
-             .. code-block:: sh
+           mount -t proc none /proc
+           mount -t sysfs none /sys
+           mount -t devtmpfs  dev  /dev
 
-                #!/bin/sh
+           # Run modetest in the background
+           # 42 - connector ID
+           # 40 - CRTC ID
+           # 1920x1200 - resolution of panel
+           (modetest -M tidss -s 42@40:1920x1200 0<&- 2>/tmp/output.log) &
 
-                mount -t proc none /proc
-                mount -t sysfs none /sys
-                mount -t devtmpfs  dev  /dev
+           # For sysvinit based flow
+           # Use either sysvinit or direct shell approach
+           # exec /sbin/init.sysvinit $*
 
-                # Run modetest in the background
-                # 40 - connector ID
-                # 38 - CRTC ID
-                # 1920x1200 - resolution of panel
-                (modetest -M tidss -s 40@38:1920x1200 0<&- 2>/tmp/output.log) &
+           # Shell - restarts automatically when exited
+           while true; do
+               /bin/sh </dev/console >/dev/console 2>&1
+           done
 
-                exec /sbin/init.sysvinit $*
+      To get the connector ID and CRTC ID of OLDI panel used, run :code:`kmsprint` or :code:`modetest -M tidss`
 
-            You can get the connector ID and CRTC ID of your OLDI panel by running :code:`kmsprint` or :code:`modetest -M tidss`
+    - Make it executable
 
-        - Make it executable
+        .. code-block:: console
+
+           $ chmod +x <filesystem>/sbin/init
 
-            .. code-block:: console
+    - Convert file system to cpio file.
+
+        .. code-block:: console
 
-                chmod +x <filesystem>/sbin/init
+           host$ cd <filesystem>
+           host$ find . | sort | cpio --reproducible -o -H newc -R root:root > ../tisdk-tiny-initramfs-new.cpio
 
+        Pass the new cpio file during kernel build.
 
 .. ifconfig:: CONFIG_part_variant in ('AM62AX')
 
