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    Subject[PATCH] ARM: cache-v7: Disable preemption when reading CCSIDR
    armv7's flush_cache_all() flushes caches via set/way. To
    determine the cache attributes (line size, number of sets,
    etc.) the assembly first writes the CSSELR register to select a
    cache level and then reads the CCSIDR register. The CSSELR register
    is banked per-cpu and is used to determine which cache level CCSIDR
    reads. If the task is migrated between when the CSSELR is written and
    the CCSIDR is read the CCSIDR value may be for an unexpected cache
    level (for example L1 instead of L2) and incorrect cache flushing
    could occur.

    Disable preemption across the write and read so that the correct
    cache attributes are read and used for the cache flushing
    routine. This fixes a problem we see in scm_call() when
    flush_cache_all() is called from preemptible context and
    sometimes the L2 cache is not properly flushed out.

    Signed-off-by: Stephen Boyd <>
    Cc: Catalin Marinas <>

    Should we move get_thread_info into assembler.h? It seems odd
    to include entry-header.S but I saw that vfp was doing the same.

    arch/arm/mm/cache-v7.S | 11 +++++++++++
    1 files changed, 11 insertions(+), 0 deletions(-)

    diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
    index 07c4bc8..a033858 100644
    --- a/arch/arm/mm/cache-v7.S
    +++ b/arch/arm/mm/cache-v7.S
    @@ -16,6 +16,7 @@
    #include <asm/unwind.h>

    #include "proc-macros.S"
    +#include "../kernel/entry-header.S"

    * v7_flush_icache_all()
    @@ -54,9 +55,19 @@ loop1:
    and r1, r1, #7 @ mask of the bits for current cache only
    cmp r1, #2 @ see what cache we have at this level
    blt skip @ skip if no cache, or just i-cache
    +#ifdef CONFIG_PREEMPT
    + get_thread_info r9
    + ldr r11, [r9, #TI_PREEMPT] @ get preempt count
    + add r11, r11, #1 @ increment it
    + str r11, [r9, #TI_PREEMPT]
    mcr p15, 2, r10, c0, c0, 0 @ select current cache level in cssr
    isb @ isb to sych the new cssr&csidr
    mrc p15, 1, r1, c0, c0, 0 @ read the new csidr
    +#ifdef CONFIG_PREEMPT
    + sub r11, r11, #1 @ decrement preempt count
    + str r11, [r9, #TI_PREEMPT]
    and r2, r1, #7 @ extract the length of the cache lines
    add r2, r2, #4 @ add 4 (line length offset)
    ldr r4, =0x3ff
    Sent by an employee of the Qualcomm Innovation Center, Inc.
    The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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