Commit 7ce236fc authored by Catalin Marinas's avatar Catalin Marinas Committed by Russell King

[ARM] 5487/1: ARM errata: Stale prediction on replaced interworking branch

This patch adds the workaround for the 430973 Cortex-A8 (r1p0..r1p2)
erratum. The BTAC/BTB is now flushed at every context switch.
Signed-off-by: default avatarCatalin Marinas <>
Signed-off-by: default avatarRussell King <>
parent 9cba3ccc
......@@ -749,6 +749,22 @@ config ARM_ERRATA_411920
It does not affect the MPCore. This option enables the ARM Ltd.
recommended workaround.
config ARM_ERRATA_430973
bool "ARM errata: Stale prediction on replaced interworking branch"
depends on CPU_V7
This option enables the workaround for the 430973 Cortex-A8
(r1p0..r1p2) erratum. If a code sequence containing an ARM/Thumb
interworking branch is replaced with another code sequence at the
same virtual address, whether due to self-modifying code or virtual
to physical address re-mapping, Cortex-A8 does not recover from the
stale interworking branch prediction. This results in Cortex-A8
executing the new code sequence in the incorrect ARM or Thumb state.
The workaround enables the BTB/BTAC operations by setting ACTLR.IBE
and also flushes the branch target cache at every context switch.
Note that setting specific bits in the ACTLR register may not be
available in non-secure mode.
source "arch/arm/common/Kconfig"
......@@ -95,6 +95,9 @@ ENTRY(cpu_v7_switch_mm)
mov r2, #0
ldr r1, [r1, #MM_CONTEXT_ID] @ get mm->
orr r0, r0, #TTB_FLAGS
#ifdef CONFIG_ARM_ERRATA_430973
mcr p15, 0, r2, c7, c5, 6 @ flush BTAC/BTB
mcr p15, 0, r2, c13, c0, 1 @ set reserved context ID
1: mcr p15, 0, r0, c2, c0, 0 @ set TTB 0
......@@ -180,6 +183,11 @@ __v7_setup:
stmia r12, {r0-r5, r7, r9, r11, lr}
bl v7_flush_dcache_all
ldmia r12, {r0-r5, r7, r9, r11, lr}
#ifdef CONFIG_ARM_ERRATA_430973
mrc p15, 0, r10, c1, c0, 1 @ read aux control register
orr r10, r10, #(1 << 6) @ set IBE to 1
mcr p15, 0, r10, c1, c0, 1 @ write aux control register
mov r10, #0
mcr p15, 0, r10, c7, c5, 0 @ I+BTB cache invalidate
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