This is a kernel build with a PHY driver for the Raspberry PI CM4
The purpose is to enable PTP features for the built-in NIC.
It must be compiled before use, and this will take a VERY long time,
4+ hours or more. That process can not be paused, so plan ahead.

Current status : 

 - The overall status is "under development" or "experimental" 
 - The driver is stable, i.e. it shouldn't crash the operating system
 - Timestamping features work, but other features do not.
 - Missing features prevent most PTP apps from working properly. 

******** This code is NOT error free and could cause unknown damage to :
	- the Operating System or files on the CM4
	- the CM4 hardware,
	- devices connected to or near the CM4
	- other items unknown.
******** USE ONLY AT YOUR OWN RISK


Install : (untested, first draft)

This version is intended only for 64 bit versions operating systems 
running on the Raspberry PI CM4. It is developed on Ubuntu 21.10 (64-bit).
It may or may not work on other 64 bit operating systems.

The steps below come from the instructions on :
https://www.raspberrypi.com/documentation/computers/linux_kernel.html
If the steps below fail, refer to that document for more info.

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1) Install prerequisites

	sudo apt install gcc g++ yasm make cmake
	sudo apt install git bc bison flex libssl-dev make

2) git-clone (download) source code

	git clone -b cm4-ptp-kylejudd https://github.com/KyleJudd/linux.git

3) Configure kernel build environment

	cd linux
	KERNEL=kernel8
	make bcm2711_defconfig

	sudo apt install libncurses5-dev
	make menuconfig

4) Configure kernel build options/flags

The last command above should cause a GUI to appear. Use this GUI to 
enable certain PTP/driver options.  This is necessary so that a .config
file is generated with required options selected.  If this is not done properly,
the code may not compile or function properly. Use instructions on screen or other
online guides to learn how to use this app.

after selecting options below, press "y" to enable. Make sure there is a "*" to the 
left of the name, not "m".

The necessary settings are (from the top page) :

"Networking Support"->"Networking Options"->"Timestamping in PHY Devices"
"Device Drivers"->"PTP clock support"
"Device Drivers"->"PTP clock support"->"Add suport for ptp in bcm54210pe PHYs"

Save config and exit.

5) Build Kernel (This could take a VERY long time, 4+ hours or more)

	make -j4 Image modules dtbs
	sudo make modules_install

6) Copy necessary files to boot directory

	sudo cp arch/arm64/boot/Image /boot/$KERNEL.img

7) Reboot Raspberry PI

	sudo reboot now
 
______________________________________________________________________


Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.