7.29. Qualcomm MSM8916
The MSM8916 platform port in TF-A supports multiple similar Qualcomm SoCs:
System-on-Chip (SoC) |
TF-A Platform |
Application CPU |
Supports |
|---|---|---|---|
Snapdragon 410 (MSM8x16, APQ8016(E)) (DragonBoard 410c) |
|
4x ARM Cortex-A53 |
AArch64/AArch32 |
Snapdragon 615 (MSM8x39, APQ8039) |
|
4x ARM Cortex-A53 4x ARM Cortex-A53 |
AArch64/AArch32 |
Snapdragon 210 (MSM8x09, APQ8009) |
|
4x ARM Cortex-A7 |
AArch32 only |
Snapdragon X5 Modem (MDM9x07) |
|
1x ARM Cortex-A7 |
AArch32 only |
It provides a minimal, community-maintained EL3 firmware and PSCI implementation, based on information from the public Snapdragon 410E Technical Reference Manual combined with a lot of trial and error to actually make it work.
Note
Unlike the QTI SC7180/SC7280 ports, this port does not make use of a proprietary binary components (QTISECLIB). It is fully open-source but therefore limited to publicly documented hardware components.
7.29.1. Functionality
The TF-A port is much more minimal compared to the original firmware and therefore expects the non-secure world (e.g. Linux) to manage more hardware, such as the SMMUs and all remote processors (RPM, WCNSS, Venus, Modem). Everything except modem is currently functional with a slightly modified version of mainline Linux.
Warning
This port is not secure. There is no special secure memory and the used DRAM is available from both the non-secure and secure worlds. Unfortunately, the hardware used for memory protection is not described in the APQ8016E documentation.
The port is primarily intended as a minimal PSCI implementation (without a
separate secure world) where this limitation is not a big problem. Booting
secondary CPU cores (PSCI CPU_ON) is supported. Basic CPU core power
management (CPU_SUSPEND) is functional but still work-in-progress and
will be added later once ready.
7.29.2. Boot Flow
BL31 (AArch64) or BL32/SP_MIN (AArch32) replaces the original tz firmware
in the boot flow:
Boot ROM (PBL) -> SBL -> BL31 (EL3) -> U-Boot (EL2) -> Linux (EL2)
After initialization the normal world starts at a fixed entry address in EL2/HYP
mode, configured using PRELOADED_BL33_BASE. At runtime, it is expected that
the normal world bootloader was already loaded into RAM by a previous firmware
component (usually SBL) and that it is capable of running in EL2/HYP mode.
U-Boot for DragonBoard 410c is recommended if possible. The original Little Kernel-based bootloader from Qualcomm does not support EL2/HYP, but can be booted using an additional shim loader such as tfalkstub.
7.29.3. Build
It is possible to build for either AArch64 or AArch32. Some platforms use 32-bit CPUs that only support AArch32 (see table above). For all others AArch64 is the preferred build option.
7.29.3.1. AArch64 (BL31)
Setup the cross compiler for AArch64 and build BL31 for one of the platforms in the table above:
$ make CROSS_COMPILE=aarch64-none-elf- PLAT=...
The BL31 ELF image is generated in build/$PLAT/release/bl31/bl31.elf.
7.29.3.2. AArch32 (BL32/SP_MIN)
Setup the cross compiler for AArch32 and build BL32 with SP_MIN for one of the platforms in the table above:
$ make CROSS_COMPILE=arm-none-eabi- PLAT=... ARCH=aarch32 AARCH32_SP=sp_min
The BL32 ELF image is generated in build/$PLAT/release/bl32/bl32.elf.
7.29.4. Build Options
Some options can be changed at build time by adding them to the make command line:
QTI_UART_NUM: Number of UART controller to use for debug output and crash reports. This must be the same UART as used by earlier boot firmware since the UART controller does not get fully initialized at the moment. Defaults to the usual debug UART used for the platform (seeplatform.mk).
QTI_RUNTIME_UART: By default (0) the UART is only used for the boot process and critical crashes. If set to1it is also used for runtime messages. Note that this option can only be used if the UART is reserved in the normal world and the necessary clocks remain enabled.
The memory region used for the different firmware components is not fixed and
can be changed on the make command line. The default values match the addresses
used by the original firmware (see platform.mk):
PRELOADED_BL33_BASE: The entry address for the normal world. Usually refers to the first bootloader (e.g. U-Boot).
BL31_BASE: Base address for the BL31 firmware component. Must point to a 64K-aligned memory region with at least 128 KiB space that is permanently reserved in the normal world.
BL32_BASE: Base address for the BL32 firmware component.
AArch32: BL32 is used in place of BL31, so the option is equivalent to
BL31_BASE.AArch64: Secure-EL1 Payload. Defaults to using 128 KiB of space directly after BL31. For testing only, the port is primarily intended as a minimal PSCI implementation without a separate secure world.
7.29.5. Installation
The ELF image must be “signed” before flashing it, even if the board has secure boot disabled. In this case the signature does not provide any security, but it provides the firmware with required metadata.
The DragonBoard 410c does not have secure boot enabled by default. In this case you can simply sign the ELF image using a randomly generated key. You can use e.g. qtestsign:
$ ./qtestsign.py tz build/msm8916/release/bl31/bl31.elf
Then install the resulting build/msm8916/release/bl31/bl31-test-signed.mbn
to the tz partition on the device. BL31 should be running after a reboot.
Note
On AArch32 the ELF image is called bl32.elf.
The installation procedure is identical.
Warning
Do not flash incorrectly signed firmware on devices that have secure boot enabled! Make sure that you have a way to recover the board in case of problems (e.g. using EDL).
7.29.6. Boot Trace
7.29.6.1. AArch64 (BL31)
BL31 prints some lines on the debug console, which will usually look like this
(with DEBUG=1, otherwise only the NOTICE lines are shown):
...
S - DDR Frequency, 400 MHz
NOTICE: BL31: v2.6(debug):v2.6
NOTICE: BL31: Built : 20:00:00, Dec 01 2021
INFO: BL31: Platform setup start
INFO: ARM GICv2 driver initialized
INFO: BL31: Platform setup done
INFO: BL31: Initializing runtime services
INFO: BL31: cortex_a53: CPU workaround for 819472 was applied
INFO: BL31: cortex_a53: CPU workaround for 824069 was applied
INFO: BL31: cortex_a53: CPU workaround for 826319 was applied
INFO: BL31: cortex_a53: CPU workaround for 827319 was applied
INFO: BL31: cortex_a53: CPU workaround for 835769 was applied
INFO: BL31: cortex_a53: CPU workaround for disable_non_temporal_hint was applied
INFO: BL31: cortex_a53: CPU workaround for 843419 was applied
INFO: BL31: cortex_a53: CPU workaround for 1530924 was applied
INFO: BL31: Preparing for EL3 exit to normal world
INFO: Entry point address = 0x8f600000
INFO: SPSR = 0x3c9
U-Boot 2021.10 (Dec 01 2021 - 20:00:00 +0000)
Qualcomm-DragonBoard 410C
...
7.29.6.2. AArch32 (BL32/SP_MIN)
BL32/SP_MIN prints some lines on the debug console, which will usually look like
this (with DEBUG=1, otherwise only the NOTICE lines are shown):
...
S - DDR Frequency, 400 MHz
NOTICE: SP_MIN: v2.8(debug):v2.8
NOTICE: SP_MIN: Built : 23:03:31, Mar 31 2023
INFO: SP_MIN: Platform setup start
INFO: ARM GICv2 driver initialized
INFO: SP_MIN: Platform setup done
INFO: SP_MIN: Initializing runtime services
INFO: BL32: cortex_a53: CPU workaround for 819472 was applied
INFO: BL32: cortex_a53: CPU workaround for 824069 was applied
INFO: BL32: cortex_a53: CPU workaround for 826319 was applied
INFO: BL32: cortex_a53: CPU workaround for 827319 was applied
INFO: BL32: cortex_a53: CPU workaround for disable_non_temporal_hint was applied
INFO: SP_MIN: Preparing exit to normal world
INFO: Entry point address = 0x86400000
INFO: SPSR = 0x1da
Android Bootloader - UART_DM Initialized!!!
[0] welcome to lk
...