plat/arm: Introduce ARM_LINUX_KERNEL_AS_BL33 build option
Normally, BL33 needs to contain a boot loader like U-Boot or UEFI that
eventually gives control to the OS. However, in some cases, this boot
sequence may be too slow. For example, when doing tests in a
cycle-accurate emulator, the user may only be interested in the
interaction between the Trusted Firmware and the OS, not in the boot
process itself.
The new option ARM_LINUX_KERNEL_AS_BL33 allows BL33 to contain the Linux
kernel image by changing the value of registers x0-x3 to the values
expected by the kernel. This option requires the device tree blob (DTB)
to be present in memory. Its address must be specified in the newly
introduced ARM_PRELOADED_DTB_BASE build option. For now, it only supports
AArch64 kernels.
This option is only available when RESET_TO_BL31=1. For this reason
the BL33 binary must be preloaded in memory and PRELOADED_BL33_BASE must
be used.
For example, if the kernel is loaded at 0x80080000 and the DTB is loaded
at address 0x82000000, the firmware could be built like this:
CROSS_COMPILE=aarch64-linux-gnu- \
make PLAT=fvp DEBUG=1 \
RESET_TO_BL31=1 \
ARM_LINUX_KERNEL_AS_BL33=1 \
PRELOADED_BL33_BASE=0x80080000 \
ARM_PRELOADED_DTB_BASE=0x82000000 \
all fip
Change-Id: If9dc847c65ae2d0c27b51f0fd44fc06b28497db9
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/docs/user-guide.rst b/docs/user-guide.rst
index aed54a6..4a8c3a1 100644
--- a/docs/user-guide.rst
+++ b/docs/user-guide.rst
@@ -590,7 +590,7 @@
firmware images have been loaded in memory, and the MMU and caches are
turned off. Refer to the "Debugging options" section for more details.
-- ``SP_MIN_WITH_SECURE_FIQ``: Boolean flag to indicate the SP_MIN handles
+- ``SP_MIN_WITH_SECURE_FIQ``: Boolean flag to indicate the SP_MIN handles
secure interrupts (caught through the FIQ line). Platforms can enable
this directive if they need to handle such interruption. When enabled,
the FIQ are handled in monitor mode and non secure world is not allowed
@@ -678,6 +678,15 @@
Trusted Watchdog may be disabled at build time for testing or development
purposes.
+- ``ARM_LINUX_KERNEL_AS_BL33``: The Linux kernel expects registers x0-x3 to
+ have specific values at boot. This boolean option allows the Trusted Firmware
+ to have a Linux kernel image as BL33 by preparing the registers to these
+ values before jumping to BL33. This option defaults to 0 (disabled). For now,
+ it only supports AArch64 kernels. ``RESET_TO_BL31`` must be 1 when using it.
+ If this option is set to 1, ``ARM_PRELOADED_DTB_BASE`` must be set to the
+ location of a device tree blob (DTB) already loaded in memory. The Linux
+ Image address must be specified using the ``PRELOADED_BL33_BASE`` option.
+
- ``ARM_RECOM_STATE_ID_ENC``: The PSCI1.0 specification recommends an encoding
for the construction of composite state-ID in the power-state parameter.
The existing PSCI clients currently do not support this encoding of