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ARM: rpi: add some missing Kconfig help text

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Add notes re: enabling the UART to the RPi 3 32-bit help text. Fully
describe the RPi 3 64-bit board option.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
This commit is contained in:
Stephen Warren 2016-04-01 21:38:04 -06:00 committed by Tom Rini
parent d22a765755
commit 158c9c78a5
1 changed files with 27 additions and 1 deletions
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28
arch/arm/mach-bcm283x/Kconfig
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@ -63,7 +63,9 @@ config TARGET_RPI_3_32B
This option assumes the VideoCore firmware is configured to use the This option assumes the VideoCore firmware is configured to use the
mini UART (rather than PL011) for the serial console. This is the mini UART (rather than PL011) for the serial console. This is the
default on the RPi 3. To enable the UART console, the following non- default on the RPi 3. To enable the UART console, the following non-
default option must be present in config.txt: enable_uart=1. default option must be present in config.txt: enable_uart=1. This is
required for U-Boot to operate correctly, even if you only care
about the HDMI/usbkbd console.
This option creates a build targetting the ARMv7/AArch32 ISA. This option creates a build targetting the ARMv7/AArch32 ISA.
select ARMV7_LPAE select ARMV7_LPAE
@ -72,6 +74,30 @@ config TARGET_RPI_3_32B
config TARGET_RPI_3 config TARGET_RPI_3
bool "Raspberry Pi 3 64-bit build" bool "Raspberry Pi 3 64-bit build"
help
Support for all BCM2837-based Raspberry Pi variants, such as
the RPi 3 model B, in AArch64 (64-bit) mode.
This option assumes the VideoCore firmware is configured to use the
mini UART (rather than PL011) for the serial console. This is the
default on the RPi 3. To enable the UART console, the following non-
default option must be present in config.txt: enable_uart=1. This is
required for U-Boot to operate correctly, even if you only care
about the HDMI/usbkbd console.
At the time of writing, the VC FW requires a non-default option in
config.txt to request the ARM CPU boot in 64-bit mode:
arm_control=0x200
The VC FW typically provides ARM "stub" code to set up the CPU and
quiesce secondary SMP CPUs. This is not currently true in 64-bit
mode. In order to boot U-Boot before the VC FW is enhanced, please
see the commit description for the commit which added RPi3 support
for a workaround. Since the instructions are temporary, they are not
duplicated here. The VC FW enhancement is tracked in
https://github.com/raspberrypi/firmware/issues/579.
This option creates a build targetting the ARMv8/AArch64 ISA.
select ARM64 select ARM64
select BCM2837 select BCM2837