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At the moment the U-Boot port for the DragonBoard 410c is designed
to be loaded as an Android boot image after Qualcomm's Little Kernel (LK)
bootloader. This is simple to set up but LK is redundant in this case,
since everything done by LK can be also done directly by U-Boot.
Dropping LK entirely has at least the following advantages:
- Easier installation/board code (no need for Android boot images)
- (Slightly) faster boot
- Boot directly in 64-bit without a round trip to 32-bit for LK
So far this was not possible yet because of unsolved problems:
1. Signing tool: The firmware expects a "signed" ELF image with extra
(Qualcomm-specific) ELF headers, usually used for secure boot.
The DragonBoard 410c does not have secure boot by default but the
extra ELF headers are still required.
2. PSCI bug: There seems to be a bug in the PSCI implementation
(part of the TrustZone/tz firmware) that causes all other CPU cores
to be started in 32-bit mode if LK is missing in the boot chain.
This causes Linux to hang early during boot.
There is a solution for both problems now:
1. qtestsign (https://github.com/msm8916-mainline/qtestsign)
can be used as a "signing" tool for U-Boot and other firmware.
2. A workaround for the "PSCI bug" is to execute the TZ syscall when
entering U-Boot. That way PSCI is made aware of the 64-bit switch
and starts all other CPU cores in 64-bit mode as well.
Simplify the dragonboard410c board by removing all the extra code that
is only used to build an Android boot image that can be loaded by LK.
This allows dropping the custom linker script, special image magic,
as well as most of the special build/installation instructions.
CONFIG_REMAKE_ELF is used to build a new ELF image that has both U-Boot
and the appended DTB combined. The resulting u-boot.elf can then be
passed to the "signing" tool (e.g. qtestsign).
The PSCI workaround is placed in the "boot0" hook that is enabled
with CONFIG_ENABLE_ARM_SOC_BOOT0_HOOK. The extra check for EL1 allows
compatibility with custom firmware that enters U-Boot in EL2 or EL3,
e.g. qhypstub (https://github.com/msm8916-mainline/qhypstub).
As a first step these changes apply only to DragonBoard410c.
Similar changes could likely also work for the DragonBoard 820c.
Note that removing LK wouldn't be possible that easily without a lot of
work already done three years ago by Ramon Fried. A lot of missing
initialization, pinctrl etc was already added back then even though
it was not strictly needed yet.
Cc: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
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When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from. So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry. Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.
In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.
This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents. There's also a few places where I found we did not have a tag
and have introduced one.
Signed-off-by: Tom Rini <trini@konsulko.com>
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This commit add support for 96Boards Dragonboard410C.
It is board based on APQ8016 Qualcomm SoC, complying with
96boards specification.
Features (present out of the box):
- 4x Cortex A53 (ARMv8)
- 2x USB Host port
- 1x USB Device port
- 4x LEDs
- 1x HDMI connector
- 1x uSD connector
- 3x buttons (Power, Vol+, Vol-/Reset)
- WIFI, Bluetooth with integrated antenna
- 8GiB eMMC
U-Boot boots chained with fastboot in 64-bit mode.
For detailed build instructions see readme.txt in board directory.
Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Tested-by: Simon Glass <sjg@chromium.org>
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