README

In this directory you can download the Raspberry Pi firmware files, which are
required to boot a Circle kernel image on a Raspberry Pi computer.

It is now always recommended to copy the file config32.txt (for 32-bit
operation, AArch32) or config64.txt (for 64-bit operation, AArch64) from this
directory to the SD card and to rename it to config.txt there.

If you want to use the FIQ on a Raspberry Pi 4, you need an additional
Circle-specific ARM stub file, which will be loaded by the firmware. This ARM
stub can be built in this directory.

FIRMWARE

To download the Raspberry Pi firmware files just enter in this directory:

	make

This will provide the following files:

	bootcode.bin		boot loader (not used on Raspberry Pi 4)
	start.elf		firmware executable for  Raspberry Pi 1-3
	start4.elf		firmware executable for  Raspberry Pi 4
	fixup.dat		relocation information for start.elf
	fixup4.dat		relocation information for start4.elf
	bcm2711-rpi-4-b.dtb	device tree binary needed for Raspberry Pi 4
	bcm2711-rpi-400.dtb	device tree binary needed for Raspberry Pi 400
	bcm2711-rpi-cm4.dtb	device tree binary needed for Compute Module 4
	bcm2710-rpi-zero-2-w.dtb device tree binary needed for Raspberry Pi Zero 2 W
	LICENCE.broadcom	firmware license
	COPYING.linux		license for the device tree binaries
	start_cd.elf		cut-down firmware for Raspberry Pi 1-3 (option)
	start4cd.elf		cut-down firmware for Raspberry Pi 4 (option)
	fixup_cd.dat		relocation information for start_cd.elf (option)
	fixup4cd.dat		relocation information for start4cd.elf (option)

The cut-down version of the firmware is used, when the option "gpu_mem=16" is
specified in config.txt. It does not support codecs and 3D, but is smaller and
loads quicker. Without this option specified, the last four files are not
needed.

In any case you have to copy these files onto the first FAT partition on a SD
card along with the kernel*.img file of your Circle application.

FIQ SUPPORT ON RASPBERRY PI 4, 400, CM4

FIQ (fast interrupt request) support on the Raspberry Pi 4, 400 and CM4 requires
an additional Circle-specific ARM stub file armstub7-rpi4.bin (AArch32) or
armstub8-rpi4.bin (AArch64). These files will be built when you enter the
following commands in this directory:

	make armstub		# armstub7-rpi4.bin for AArch32
	make armstub64		# armstub8-rpi4.bin for AArch64

The build process uses the same toolchain, which is used to build Circle kernel
images. The toolchain prefix (PREFIX= or PREFIX64=) can be configured in the
file Config.mk in the Circle root directory. You have to copy the created file
armstub?-rpi4.bin to the SD card together with the other files (see above).

QUICK INSTALL

If you have defined the path to the mount point of your SD card as follows in
the file Config.mk or Config2.mk, you can quickly create a boot-able SD card
with all required files and the serial bootloader:

	SDCARD = /path/to/your/sd/card

Enter one of the following commands to create the SD card. The SD card must
contain a FAT partition as first partition, which should be empty.

	make install		# for 32 and 64 bit operation
	make install32		# for 32 bit operation only
	make install64		# for 64 bit operation only

For "make install" both toolchains (32- and 64-bit) must be available.