[PATCH 4/7] ARM: hw_breakpoint: don't try to clear v6 debug registers during boot

[sboyd@codeaurora.org (Stephen Boyd)]

On 10/17/12 08:31, Will Deacon wrote:
> v6 cores do not provide a way to clear the debug registers without first
> enabling monitor mode, meaning that we could take spurious debug
> exceptions. Instead, rely on the registers being in a sane state when we
> boot as they are defined to be disabled out of reset anyway.
>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Tested-by: Stephen Boyd <sboyd@codeaurora.org>

> ---
>  arch/arm/kernel/hw_breakpoint.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
> index e76cf1a..b6f4aec 100644
> --- a/arch/arm/kernel/hw_breakpoint.c
> +++ b/arch/arm/kernel/hw_breakpoint.c
> @@ -912,8 +912,8 @@ static void reset_ctrl_regs(void *unused)
>  	switch (debug_arch) {
>  	case ARM_DEBUG_ARCH_V6:
>  	case ARM_DEBUG_ARCH_V6_1:
> -		/* ARMv6 cores just need to reset the registers. */
> -		goto reset_regs;
> +		/* ARMv6 cores clear the registers out of reset. */
> +		goto out_mdbgen;
>  	case ARM_DEBUG_ARCH_V7_ECP14:
>  		/*
>  		 * Ensure sticky power-down is clear (i.e. debug logic is
> @@ -966,7 +966,6 @@ clear_vcr:
>  		return;
>  	}
>  
> -reset_regs:
>  	/*
>  	 * The control/value register pairs are UNKNOWN out of reset so
>  	 * clear them to avoid spurious debug events.
> @@ -991,6 +990,7 @@ reset_regs:
>  	 * Have a crack at enabling monitor mode. We don't actually need
>  	 * it yet, but reporting an error early is useful if it fails.
>  	 */
> +out_mdbgen:
>  	if (enable_monitor_mode())
>  		cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
>  }


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