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--- en:c2_building_rt_kernel [2016/04/05 10:09]
odroid created
+++ en:c2_building_rt_kernel [2016/10/06 11:38]
moon.linux [Checkout]
@@ Line 1: / Line 1: @@
-*Template*
+====== Odroid C2 Real Time Kernel ======
+The standard Linux kernel only meets soft real-time requirements: it provides basic POSIX operations for userspace time handling
+but has no guarantees for hard timing deadlines. With Ingo Molnar's Realtime Preemption patch
+(referenced to as RT-Preempt in this document) and Thomas Gleixner's generic clock event layer with high resolution support,
+the kernel gains hard realtime capabilities.
+The RT-Preempt patch has raised quite some interest throughout the industry.
+Its clean design and consequent aim towards mainline integration makes it an interesting option for hard and firm realtime applications,
+reaching from professional audio to industrial control.
+Goals of RT kernel
+    Making in-kernel locking-primitives (using spinlocks) preemptible though reimplementation with rtmutexes:
+    Critical sections protected by i.e. spinlock_t and rwlock_t are now preemptible.
+    Implementing priority inheritance for in-kernel mutexes, spinlocks and rw_semaphores.
+    Converting interrupt handlers into preemptible kernel threads
+    Converting the old Linux timer API into separate infrastructures for high resolution kernel timers plus one for timeouts,
+    leading to userspace POSIX timers with high resolution.
+====== Build RT kernel ======
+To build RT kernel we need to update the kernel with Real time kernel patches.
+RT Patches file can be found on https://www.kernel.org/pub/linux/kernel/projects/rt/
+Latest Patches for 3.14.x can be found on https://www.kernel.org/pub/linux/kernel/projects/rt/3.14/
+==== Checkout ====
+You can checkout Linux kernel source tree from **[[https://github.com/hardkernel/linux/tree/odroidc2-3.14.y|Hardkernel's Github]]**.
+=== RT Linux Kernel ===
+Note: RT patches depend on the kernel version, so choose the relevant patch series.
+<code>
+$ git clone --depth 1 -b odroidc2-3.14.y https://github.com/hardkernel/linux.git odroidc2-3.14.y-rt
+$ cd odroidc2-3.14.y-rt
+$ wget https://www.kernel.org/pub/linux/kernel/projects/rt/3.14/older/patch-3.14.65-rt68.patch.gz
+$ zcat patch-3.14.65-rt68.patch.gz > patch-3.14.65-rt68.patch
+$ patch -p1 < patch-3.14.65-rt68.patch
+</code>
+**Note:** Arc arm64 rt kernel have some missing patches so we have to update the kernel for
+Following patches need to be applied to build the kernel.
+**Note:** These patches can be found in 3.18.y-rt patch series.
+<code>
+arm64: Mark PMU interrupt IRQF_NO_THREAD.patch
+arm64: Allow forced irq threading.patch
+arch/arm64: Add lazy preempt support.patch
+arm64: replace read_lock to rcu lock in call_step_hook
+</code>
+**Note:** Few file have conflict so you need to update manually these patches before build the kernel.
+**Note:** Please find the links for all the updated patch in the following repository.
+https://github.com/moonlinux/linux/tree/odroidc2-3.14.y-rt
+==== BuildRT Linux Kernel ====
+Kernel Configuration for RT Full Preemptible Kernel.
+Select following options to build the kernel.
+<code>
+Kernel Features  --->
+   Preemption Model (Fully Preemptible Kernel (RT)) --->
+       (X) Fully Preemptible Kernel (RT) --->
+</code>
+**Note:** update the odroidc2_defconfig with current modified.
+<code>
+$ cp .config arch/arm64/configs/odroidc2_defconfig
+</code>
+Then, Update your ODROID's kernel.
+You must do kernel configuration for ODROID-C2, then start to build. Adding -j option on make command will help you to finish compiling faster.
+<code>
+$ make odroidc2_defconfig
+$ make <-j4> Image dtbs modules
+</code>
+You have done to compile the Linux kernel (Image), the device tree file (.dtb) and kernel modules (.ko).
+<WRAP center round important 100%>
+** This explanation assume that your USB memory CARD reader is assigned at /dev/sdc. Be careful!**
+</WRAP>
+. Plug the Boot-Device(eMMC or SD) into the USB memory CARD reader and Connect the USB memory CARD reader to your HOST PC(Linux OS).
+. Copy the Image and DT(meson64_odroidc2.dtb) to the FAT partition(1st partition) in the Boot-Device.
+<code>
+$ mkdir -p mount
+$ sudo mount /dev/sdc1 ./mount
+$ sudo cp arch/arm64/boot/Image arch/arm64/boot/dts/meson64_odroidc2.dtb ./mount && sync && sudo umount ./mount
+</code>
+. Copy the driver modules to the EXT4 partition(2nd partition) in the Boot-Device.
+<code>
+$ sudo mount /dev/sdc2 ./mount
+$ sudo make modules_install ARCH=arm64 INSTALL_MOD_PATH=./mount && sync && sudo umount ./mount
+$ rm -rf mount
+</code>