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    Subject[PATCH 01/16] arm64: Use arch_timer_get_rate when trapping CNTFRQ_EL0
    Date
    In an ideal world, CNTFRQ_EL0 always contains the timer frequency
    for the kernel to use. Sadly, we get quite a few broken systems
    where the firmware authors cannot be bothered to program that
    register on all CPUs, and rely on DT to provide that frequency.

    So when trapping CNTFRQ_EL0, make sure to return the actual rate
    (as known by the kernel), and not CNTFRQ_EL0.

    Acked-by: Mark Rutland <mark.rutland@arm.com>
    Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
    ---
    arch/arm64/kernel/traps.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
    index c7c7088097be..b02295673216 100644
    --- a/arch/arm64/kernel/traps.c
    +++ b/arch/arm64/kernel/traps.c
    @@ -519,7 +519,7 @@ static void cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
    {
    int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT;

    - pt_regs_write_reg(regs, rt, read_sysreg(cntfrq_el0));
    + pt_regs_write_reg(regs, rt, arch_timer_get_rate());
    regs->pc += 4;
    }

    --
    2.11.0
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