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b4e49e3fe4
Update the MSM8916 platform documentation with the new build options introduced in the previous changes: - AArch32 (BL32/SP_MIN) - UART selection While at it, also document the build options that allow changing the memory addresses (PRELOADED_BL33_BASE, BL31_BASE, BL32_BASE). Change-Id: I2370c8264982317693f69fda0b03a255f12bafe2 Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
194 lines
8.3 KiB
ReStructuredText
194 lines
8.3 KiB
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Qualcomm Snapdragon 410 (MSM8916/APQ8016)
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=========================================
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The `Qualcomm Snapdragon 410`_ is Qualcomm's first 64-bit SoC, released in 2014
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with four ARM Cortex-A53 cores. There are differents variants (MSM8916,
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APQ8016(E), ...) that are all very similar. A popular device based on APQ8016E
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is the `DragonBoard 410c`_ single-board computer, but the SoC is also used in
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various mid-range smartphones/tablets.
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The TF-A port for MSM8916 provides a minimal, community-maintained
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EL3 firmware. It is primarily based on information from the public
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`Snapdragon 410E Technical Reference Manual`_ combined with a lot of
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trial and error to actually make it work.
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.. note::
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Unlike the :doc:`QTI SC7180/SC7280 <qti>` ports, this port does **not**
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make use of a proprietary binary components (QTISECLIB). It is fully
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open-source but therefore limited to publicly documented hardware
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components.
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Functionality
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-------------
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The TF-A port is much more minimal compared to the original firmware and
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therefore expects the non-secure world (e.g. Linux) to manage more hardware,
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such as the SMMUs and all remote processors (RPM, WCNSS, Venus, Modem).
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Everything except modem is currently functional with a slightly modified version
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of mainline Linux.
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.. warning::
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This port is **not secure**. There is no special secure memory and the
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used DRAM is available from both the non-secure and secure worlds.
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Unfortunately, the hardware used for memory protection is not described
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in the APQ8016E documentation.
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The port is primarily intended as a minimal PSCI implementation (without a
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separate secure world) where this limitation is not a big problem. Booting
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secondary CPU cores (PSCI ``CPU_ON``) is supported. Basic CPU core power
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management (``CPU_SUSPEND``) is functional but still work-in-progress and
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will be added later once ready.
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Boot Flow
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---------
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BL31 (AArch64) or BL32/SP_MIN (AArch32) replaces the original ``tz`` firmware
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in the boot flow::
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Boot ROM (PBL) -> SBL -> BL31 (EL3) -> U-Boot (EL2) -> Linux (EL2)
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After initialization the normal world starts at a fixed entry address in EL2/HYP
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mode, configured using ``PRELOADED_BL33_BASE``. At runtime, it is expected that
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the normal world bootloader was already loaded into RAM by a previous firmware
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component (usually SBL) and that it is capable of running in EL2/HYP mode.
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`U-Boot for DragonBoard 410c`_ is recommended if possible. The original Little
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Kernel-based bootloader from Qualcomm does not support EL2/HYP, but can be
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booted using an additional shim loader such as `tfalkstub`_.
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Build
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-----
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It is possible to build for either AArch64 or AArch32. AArch64 is the preferred
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build option.
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AArch64 (BL31)
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^^^^^^^^^^^^^^
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Setup the cross compiler for AArch64 and build BL31 for ``msm8916``::
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$ make CROSS_COMPILE=aarch64-none-elf- PLAT=msm8916
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The BL31 ELF image is generated in ``build/msm8916/release/bl31/bl31.elf``.
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AArch32 (BL32/SP_MIN)
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^^^^^^^^^^^^^^^^^^^^^
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Setup the cross compiler for AArch32 and build BL32 with SP_MIN for ``msm8916``::
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$ make CROSS_COMPILE=arm-none-eabi- PLAT=msm8916 ARCH=aarch32 AARCH32_SP=sp_min
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The BL32 ELF image is generated in ``build/msm8916/release/bl32/bl32.elf``.
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Build Options
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-------------
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Some options can be changed at build time by adding them to the make command line:
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* ``QTI_UART_NUM``: Number of UART controller to use for debug output and crash
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reports. This must be the same UART as used by earlier boot firmware since
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the UART controller does not get fully initialized at the moment. Defaults to
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the usual debug UART used for the platform (see ``platform.mk``).
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* ``QTI_RUNTIME_UART``: By default (``0``) the UART is only used for the boot
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process and critical crashes. If set to ``1`` it is also used for runtime
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messages. Note that this option can only be used if the UART is reserved in
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the normal world and the necessary clocks remain enabled.
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The memory region used for the different firmware components is not fixed and
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can be changed on the make command line. The default values match the addresses
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used by the original firmware (see ``platform.mk``):
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* ``PRELOADED_BL33_BASE``: The entry address for the normal world. Usually
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refers to the first bootloader (e.g. U-Boot).
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* ``BL31_BASE``: Base address for the BL31 firmware component. Must point to
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a 64K-aligned memory region with at least 128 KiB space that is permanently
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reserved in the normal world.
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* ``BL32_BASE``: Base address for the BL32 firmware component.
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* **AArch32:** BL32 is used in place of BL31, so the option is equivalent to
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``BL31_BASE``.
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* **AArch64:** Secure-EL1 Payload. Defaults to using 128 KiB of space
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directly after BL31. For testing only, the port is primarily intended as
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a minimal PSCI implementation without a separate secure world.
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Installation
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------------
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The ELF image must be "signed" before flashing it, even if the board has secure
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boot disabled. In this case the signature does not provide any security,
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but it provides the firmware with required metadata.
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The `DragonBoard 410c`_ does not have secure boot enabled by default. In this
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case you can simply sign the ELF image using a randomly generated key. You can
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use e.g. `qtestsign`_::
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$ ./qtestsign.py tz build/msm8916/release/bl31/bl31.elf
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Then install the resulting ``build/msm8916/release/bl31/bl31-test-signed.mbn``
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to the ``tz`` partition on the device. BL31 should be running after a reboot.
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.. note::
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On AArch32 the ELF image is called ``bl32.elf``.
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The installation procedure is identical.
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.. warning::
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Do not flash incorrectly signed firmware on devices that have secure
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boot enabled! Make sure that you have a way to recover the board in case
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of problems (e.g. using EDL).
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Boot Trace
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----------
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AArch64 (BL31)
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^^^^^^^^^^^^^^
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BL31 prints some lines on the debug console, which will usually look like this
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(with ``DEBUG=1``, otherwise only the ``NOTICE`` lines are shown)::
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...
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S - DDR Frequency, 400 MHz
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NOTICE: BL31: v2.6(debug):v2.6
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NOTICE: BL31: Built : 20:00:00, Dec 01 2021
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INFO: BL31: Platform setup start
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INFO: ARM GICv2 driver initialized
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INFO: BL31: Platform setup done
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INFO: BL31: Initializing runtime services
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INFO: BL31: cortex_a53: CPU workaround for 819472 was applied
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INFO: BL31: cortex_a53: CPU workaround for 824069 was applied
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INFO: BL31: cortex_a53: CPU workaround for 826319 was applied
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INFO: BL31: cortex_a53: CPU workaround for 827319 was applied
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INFO: BL31: cortex_a53: CPU workaround for 835769 was applied
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INFO: BL31: cortex_a53: CPU workaround for disable_non_temporal_hint was applied
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INFO: BL31: cortex_a53: CPU workaround for 843419 was applied
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INFO: BL31: cortex_a53: CPU workaround for 1530924 was applied
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INFO: BL31: Preparing for EL3 exit to normal world
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INFO: Entry point address = 0x8f600000
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INFO: SPSR = 0x3c9
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U-Boot 2021.10 (Dec 01 2021 - 20:00:00 +0000)
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Qualcomm-DragonBoard 410C
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...
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AArch32 (BL32/SP_MIN)
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^^^^^^^^^^^^^^^^^^^^^
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BL32/SP_MIN prints some lines on the debug console, which will usually look like
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this (with ``DEBUG=1``, otherwise only the ``NOTICE`` lines are shown)::
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...
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S - DDR Frequency, 400 MHz
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NOTICE: SP_MIN: v2.8(debug):v2.8
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NOTICE: SP_MIN: Built : 23:03:31, Mar 31 2023
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INFO: SP_MIN: Platform setup start
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INFO: ARM GICv2 driver initialized
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INFO: SP_MIN: Platform setup done
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INFO: SP_MIN: Initializing runtime services
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INFO: BL32: cortex_a53: CPU workaround for 819472 was applied
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INFO: BL32: cortex_a53: CPU workaround for 824069 was applied
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INFO: BL32: cortex_a53: CPU workaround for 826319 was applied
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INFO: BL32: cortex_a53: CPU workaround for 827319 was applied
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INFO: BL32: cortex_a53: CPU workaround for disable_non_temporal_hint was applied
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INFO: SP_MIN: Preparing exit to normal world
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INFO: Entry point address = 0x86400000
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INFO: SPSR = 0x1da
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Android Bootloader - UART_DM Initialized!!!
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[0] welcome to lk
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...
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.. _Qualcomm Snapdragon 410: https://www.qualcomm.com/products/snapdragon-processors-410
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.. _DragonBoard 410c: https://www.96boards.org/product/dragonboard410c/
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.. _Snapdragon 410E Technical Reference Manual: https://developer.qualcomm.com/download/sd410/snapdragon-410e-technical-reference-manual.pdf
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.. _U-Boot for DragonBoard 410c: https://u-boot.readthedocs.io/en/latest/board/qualcomm/dragonboard410c.html
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.. _qtestsign: https://github.com/msm8916-mainline/qtestsign
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.. _tfalkstub: https://github.com/msm8916-mainline/tfalkstub
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