rpi3: Update documentation
Add information about direct Linux kernel boot for kernels that support PSCI. Change-Id: I05f76aa36398edabf411cb25a646437af1862e6e Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
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Antonio Nino Diaz
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@ -7,8 +7,7 @@ Trusted Firmware-A for Raspberry Pi 3
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.. contents::
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The `Raspberry Pi 3`_ is an inexpensive single-board computer that contains four
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Arm Cortex-A53 cores, which makes it possible to have a port of Trusted
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Firmware-A (TF-A).
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Arm Cortex-A53 cores.
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The following instructions explain how to use this port of the TF-A with the
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default distribution of `Raspbian`_ because that's the distribution officially
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@ -66,7 +65,7 @@ Placement of images
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The file ``armstub8.bin`` contains BL1 and the FIP. It is needed to add padding
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between them so that the addresses they are loaded to match the ones specified
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when compiling TF-A.
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when compiling TF-A. This is done automatically by the build system.
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The device tree block is loaded by the VideoCore loader from an appropriate
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file, but we can specify the address it is loaded to in ``config.txt``.
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@ -159,14 +158,24 @@ The `Linux kernel tree`_ has instructions on how to jump to the Linux kernel
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in ``Documentation/arm/Booting`` and ``Documentation/arm64/booting.txt``. The
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bootstrap should take care of this.
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This port support a direct boot of the Linux kernel from the firmware (as a BL33
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image). Alternatively, U-Boot or other bootloaders may be used.
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Secondary cores
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~~~~~~~~~~~~~~~
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This port of the Trusted Firmware-A supports ``PSCI_CPU_ON``,
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`PSCI_SYSTEM_RESET`` and ``PSCI_SYSTEM_OFF``. The last one doesn't really turn
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the system off, it simply reboots it and asks the VideoCore firmware to keep it
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in a low power mode permanently.
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The kernel used by `Raspbian`_ doesn't have support for PSCI, so it is needed to
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use mailboxes to trap the secondary cores until they are ready to jump to the
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kernel. This mailbox is located at a different address in the AArch32 default
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kernel than in the AArch64 kernel.
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Kernels with PSCI support can use the PSCI calls instead for a cleaner boot.
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Also, this port of TF-A has another Trusted Mailbox in Shared BL RAM. During
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cold boot, all secondary cores wait in a loop until they are given given an
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address to jump to in this Mailbox (``bl31_warm_entrypoint``).
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@ -187,43 +196,38 @@ To boot a AArch32 kernel, both AArch64 and AArch32 toolchains are required. The
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AArch32 toolchain is needed for the AArch32 bootstrap needed to load a 32-bit
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kernel.
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First, clone and compile `Raspberry Pi 3 TF-A bootstrap`_. Choose the one
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needed for the architecture of your kernel.
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Then compile TF-A. For a AArch32 kernel, use the following command line:
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.. code:: shell
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CROSS_COMPILE=aarch64-linux-gnu- make PLAT=rpi3 \
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RPI3_BL33_IN_AARCH32=1 \
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BL33=../rpi3-arm-tf-bootstrap/aarch32/el2-bootstrap.bin
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For a AArch64 kernel, use this other command line:
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.. code:: shell
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CROSS_COMPILE=aarch64-linux-gnu- make PLAT=rpi3 \
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BL33=../rpi3-arm-tf-bootstrap/aarch64/el2-bootstrap.bin
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The build system concatenates BL1 and the FIP so that the addresses match the
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ones in the memory map. The resulting file is ``armstub8.bin``, located in the
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build folder (e.g. ``build/rpi3/debug/armstub8.bin``). Now, follow the
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instructions in `Setup SD card`_.
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build folder (e.g. ``build/rpi3/debug/armstub8.bin``). To know how to use this
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file, follow the instructions in `Setup SD card`_.
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The following build options are supported:
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- ``ENABLE_STACK_PROTECTOR``: Disabled by default. It uses the hardware RNG of
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the board.
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- ``PRELOADED_BL33_BASE``: Specially useful because the file ``kernel8.img`` can
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be loaded anywhere by modifying the file ``config.txt``. It doesn't have to
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contain a kernel, it could have any arbitrary payload.
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- ``RPI3_BL33_IN_AARCH32``: This port can load a AArch64 or AArch32 BL33 image.
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By default this option is 0, which means that TF-A will jump to BL33 in EL2
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in AArch64 mode. If set to 1, it will jump to BL33 in Hypervisor in AArch32
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mode.
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- ``PRELOADED_BL33_BASE``: Used to specify the address of a BL33 binary that has
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been preloaded by any other system than using the firmware. ``BL33`` isn't
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needed in the build command line if this option is used. Specially useful
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because the file ``kernel8.img`` can be loaded anywhere by modifying the file
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``config.txt``. It doesn't have to contain a kernel, it could have any
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arbitrary payload.
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- ``RPI3_DIRECT_LINUX_BOOT``: Disabled by default. Set to 1 to enable the direct
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boot of the Linux kernel from the firmware. Option ``RPI3_PRELOADED_DTB_BASE``
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is mandatory when the direct Linux kernel boot is used. Options
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``PRELOADED_BL33_BASE`` will most likely be needed as well because it is
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unlikely that the kernel image will fit in the space reserved for BL33 images.
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This option can be combined with ``RPI3_BL33_IN_AARCH32`` in order to boot a
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32-bit kernel. The only thing this option does is to set the arguments in
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registers x0-x3 or r0-r2 as expected by the kernel.
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- ``RPI3_PRELOADED_DTB_BASE``: Auxiliary build option needed when using
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``RPI3_DIRECT_LINUX_BOOT=1``. This option allows to specify the location of a
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DTB in memory.
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- ``BL32``: This port can load and run OP-TEE. The OP-TEE image is optional.
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Please use the code from `here <https://github.com/OP-TEE/optee_os>`__.
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Build the Trusted Firmware with option ``BL32=tee-header_v2.bin
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@ -236,15 +240,16 @@ The following build options are supported:
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This will unfortunately reduce the performance of the USB driver. It is needed
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when using Raspbian, for example.
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- ``TRUSTED_BOARD_BOOT``: This port supports TBB. Set this option
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``TRUSTED_BOARD_BOOT=1`` to enable it. In order to use TBB, you might
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want to set ``GENERATE_COT=1`` to let the contents of the FIP automatically
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signed by the build process. The ROT key will be generated and output to
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``rot_key.pem`` in the build directory. It is able to set ROT_KEY to
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your own key in PEM format.
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Also in order to build, you need to clone mbedtls from
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`here <https://github.com/ARMmbed/mbedtls>`__.
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And set MBEDTLS_DIR to mbedtls source directory.
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- ``TRUSTED_BOARD_BOOT``: This port supports TBB. Set this option to 1 to enable
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it. In order to use TBB, you might want to set ``GENERATE_COT=1`` to let the
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contents of the FIP automatically signed by the build process. The ROT key
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will be generated and output to ``rot_key.pem`` in the build directory. It is
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able to set ROT_KEY to your own key in PEM format. Also in order to build,
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you need to clone mbed TLS from `here <https://github.com/ARMmbed/mbedtls>`__.
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``MBEDTLS_DIR`` must point at the mbed TLS source directory.
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- ``ENABLE_STACK_PROTECTOR``: Disabled by default. It uses the hardware RNG of
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the board.
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The following is not currently supported:
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@ -259,6 +264,60 @@ The following is not currently supported:
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able to print error messages during early crashes before setting up the
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multi console API.
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Building the firmware for kernels that don't support PSCI
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This is the case for the 32-bit image of Raspbian, for example. 64-bit kernels
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always support PSCI, but they may not know that the system understands PSCI due
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to an incorrect DTB file.
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First, clone and compile the 32-bit version of the `Raspberry Pi 3 TF-A
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bootstrap`_. Choose the one needed for the architecture of your kernel.
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Then compile TF-A. For a 32-bit kernel, use the following command line:
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.. code:: shell
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CROSS_COMPILE=aarch64-linux-gnu- make PLAT=rpi3 \
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RPI3_BL33_IN_AARCH32=1 \
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BL33=../rpi3-arm-tf-bootstrap/aarch32/el2-bootstrap.bin
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For a 64-bit kernel, use this other command line:
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.. code:: shell
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CROSS_COMPILE=aarch64-linux-gnu- make PLAT=rpi3 \
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BL33=../rpi3-arm-tf-bootstrap/aarch64/el2-bootstrap.bin
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However, enabling PSCI support in a 64-bit kernel is really easy. In the
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repository `Raspberry Pi 3 TF-A bootstrap`_ there is a patch that can be applied
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to the Linux kernel tree maintained by the Raspberry Pi foundation. It modifes
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the DTS to tell the kernel to use PSCI. Once this patch is applied, follow the
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instructions in `AArch64 kernel build instructions`_ to get a working 64-bit
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kernel image and supporting files.
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Building the firmware for kernels that support PSCI
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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For a 64-bit kernel:
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.. code:: shell
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CROSS_COMPILE=aarch64-linux-gnu- make PLAT=rpi3 \
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PRELOADED_BL33_BASE=0x01000000 \
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RPI3_PRELOADED_DTB_BASE=0x02000000 \
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RPI3_DIRECT_LINUX_BOOT=1
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For a 32-bit kernel:
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.. code:: shell
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CROSS_COMPILE=aarch64-linux-gnu- make PLAT=rpi3 \
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PRELOADED_BL33_BASE=0x01000000 \
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RPI3_PRELOADED_DTB_BASE=0x02000000 \
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RPI3_DIRECT_LINUX_BOOT=1 \
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RPI3_BL33_IN_AARCH32=1
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AArch64 kernel build instructions
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---------------------------------
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@ -275,7 +334,7 @@ allows the user to run 64-bit binaries in addition to 32-bit binaries.
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.. code:: shell
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git clone --depth=1 -b rpi-4.14.y https://github.com/raspberrypi/linux
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git clone --depth=1 -b rpi-4.18.y https://github.com/raspberrypi/linux
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cd linux
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2. Configure and compile the kernel. Adapt the number after ``-j`` so that it is
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@ -295,6 +354,7 @@ allows the user to run 64-bit binaries in addition to 32-bit binaries.
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cp arch/arm64/boot/Image /path/to/boot/kernel8.img
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cp arch/arm64/boot/dts/broadcom/bcm2710-rpi-3-b.dtb /path/to/boot/
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cp arch/arm64/boot/dts/broadcom/bcm2710-rpi-3-b-plus.dtb /path/to/boot/
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4. Install the kernel modules. Replace the path by the corresponding path to the
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filesystem partition of the SD card on your computer.
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