tree 3e262570e5ca8e739c33057b9e80bfa6d2077d22
parent 182a6f73ec6bc83ce9b72eec20fa1c6901338c16
author Will Deacon <will.deacon@arm.com> 1368028872 +0100
committer Catalin Marinas <catalin.marinas@arm.com> 1368441896 +0100

arm64: debug: clear mdscr_el1 instead of taking the OS lock

During boot, we take the debug OS lock before interrupts are enabled.
This is required to prevent clearing of PSTATE.D on the interrupt entry
path, which could result in spurious debug exceptions before we've got
round to resetting things like the hardware breakpoints registers to a
sane state.

A problem with this approach is that taking the OS lock prevents an
external JTAG debugger from debugging the system, which is especially
irritating during boot, where JTAG debugging can be most useful.

This patch clears mdscr_el1 rather than taking the lock, clearing the
MDE and KDE bits and preventing self-hosted hardware debug exceptions
from occurring.

Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: stable@vger.kernel.org