| Message ID | 1308577229-23681-5-git-send-email-dave.martin@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting index 4e686a2..a341d87 100644 --- a/Documentation/arm/Booting +++ b/Documentation/arm/Booting @@ -164,3 +164,8 @@ In either case, the following conditions must be met: - The boot loader is expected to call the kernel image by jumping directly to the first instruction of the kernel image. + On CPUs supporting the ARM instruction set, the entry must be + made in ARM state, even for a Thumb-2 kernel. + + On CPUs supporting only the Thumb instruction set such as + Cortex-M class CPUs, the entry must be made in Thumb state.
Currently, the kernel entry requirements are not explicit about whether the kernel should be entered in ARM or Thumb-2. Now that the boot protocol consistently requires the kernel Image or zImage to be entered in ARM state, document this requirement explicitly. A different rule will be needed for Cortex-M class CPUs as and when support for these lands upstream, since these CPUs don't support the ARM instruction set at all: a note is added to the effect that the kernel must be entered in Thumb on such systems. Signed-off-by: Dave Martin <dave.martin@linaro.org> --- Documentation/arm/Booting | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)