From mboxrd@z Thu Jan  1 00:00:00 1970
From: santosh.shilimkar@ti.com (Santosh Shilimkar)
Date: Fri, 11 Jan 2013 19:10:22 +0530
Subject: [PATCHv2 08/11] arm: arch_timer: add arch_counter_set_user_access
In-Reply-To: <1357747640-18594-9-git-send-email-mark.rutland@arm.com>
References: <1357747640-18594-1-git-send-email-mark.rutland@arm.com>
 <1357747640-18594-9-git-send-email-mark.rutland@arm.com>
Message-ID: <50F01646.4010203@ti.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wednesday 09 January 2013 09:37 PM, Mark Rutland wrote:
> Several bits in CNTKCTL reset to 0, including PL0VTEN. For platforms
> using the generic timer which wish to have a fast gettimeofday vDSO
> implementation, these bits must be set to 1 by the kernel. On other
> platforms, the bootloader might enable userspace access when we don't
> want it.
>
> This patch adds arch_counter_set_user_access, which sets the PL0 access
> permissions to that required by the platform. For arm, this currently
minor nit.
s/arm/ARM

> means disabling all userspace access.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> ---
>   arch/arm/include/asm/arch_timer.h |   11 +++++++++++
>   arch/arm/kernel/arch_timer.c      |    2 ++
>   2 files changed, 13 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
> index 701f2b7..05e3593 100644
> --- a/arch/arm/include/asm/arch_timer.h
> +++ b/arch/arm/include/asm/arch_timer.h
> @@ -108,6 +108,17 @@ static inline u64 arch_counter_get_cntvct(void)
>   	return cval;
>   }
>
> +static inline void __cpuinit arch_counter_set_user_access(void)
> +{
> +	u32 cntkctl;
> +
> +	asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl));
> +
> +	/* disable user access to everything */
> +	cntkctl &= ~((3 << 8) | (7 << 0));
> +
> +	asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
> +}
>
>   #else
>   static inline int arch_timer_of_register(void)
> diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
> index 834d347..4f39e68 100644
> --- a/arch/arm/kernel/arch_timer.c
> +++ b/arch/arm/kernel/arch_timer.c
> @@ -155,6 +155,8 @@ static int __cpuinit arch_timer_setup(struct clock_event_device *clk)
>   			enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0);
>   	}
>
> +	arch_counter_set_user_access();
So how do you expect platform to enabled the user-space access in case
they want to access it for some cases.

Regards
Santosh