Commit 416bcf21 authored by Doug Anderson's avatar Doug Anderson Committed by Russell King
Browse files

ARM: 8559/1: errata: Workaround erratum A12 821420 



This erratum has a very simple workaround (set a bit in a register), so
let's apply it.  Apparently the workaround's downside is a very slight
power impact.

Note that applying this errata fixes deadlocks that are easy to
reproduce with real world applications.

The arguments for why this needs to be in the kernel are similar to the
arugments made in the patch "Workaround errata A12 818325/852422 A17
852423".

Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 62c0f4a5

arch/arm/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -1200,6 +1200,16 @@ config ARM_ERRATA_818325_852422 
	  Feature Register. This bit disables an optimisation applied to a

	  sequence of 2 instructions that use opposing condition codes.



config ARM_ERRATA_821420

	bool "ARM errata: A12: sequence of VMOV to core registers might lead to a dead lock"

	depends on CPU_V7

	help

	  This option enables the workaround for the 821420 Cortex-A12

	  (all revs) erratum. In very rare timing conditions, a sequence

	  of VMOV to Core registers instructions, for which the second

	  one is in the shadow of a branch or abort, can lead to a

	  deadlock when the VMOV instructions are issued out-of-order.



config ARM_ERRATA_852423

	bool "ARM errata: A17: some seqs of opposed cond code instrs => deadlock or corruption"

	depends on CPU_V7

arch/arm/mm/proc-v7.S

+5 −0
Original line number Diff line number Diff line
@@ -367,6 +367,11 @@ __ca12_errata: 
	mrc	p15, 0, r10, c15, c0, 1		@ read diagnostic register

	orr	r10, r10, #1 << 12		@ set bit #12

	mcr	p15, 0, r10, c15, c0, 1		@ write diagnostic register

#endif

#ifdef CONFIG_ARM_ERRATA_821420

	mrc	p15, 0, r10, c15, c0, 2		@ read internal feature reg

	orr	r10, r10, #1 << 1		@ set bit #1

	mcr	p15, 0, r10, c15, c0, 2		@ write internal feature reg

#endif

	b	__errata_finish

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