[PATCH] clocksource: arch_timer: Only use the virtual counter (CNTVCT) on arm64

[Daniel Lezcano]

On 12/10/2014 12:02 PM, Catalin Marinas wrote:
> Commit 0b46b8a718c6 (clocksource: arch_timer: Fix code to use physical
> timers when requested) introduces the use of physical counters in the
> ARM architected timer driver. However, he arm64 kernel uses CNTVCT in
> VDSO. When booting in EL2, the kernel switches to the physical timers to
> make things easier for KVM but it continues to use the virtual counter
> both in user and kernel. While in such scenario CNTVCT == CNTPCT (since
> CNTVOFF is initialised by the kernel to 0), we want to spot firmware
> bugs corrupting CNTVOFF early (which would affect CNTVCT).
>
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> Tested-by: Yingjoe Chen <yingjoe.chen at mediatek.com>
> Cc: Daniel Lezcano <daniel.lezcano at linaro.org>
> ---
>
> Daniel,
>
> Do you plan to take this patch and push into mainline (ideally before -rc1)?
> Otherwise we can push it via the arm64 tree.

I will take care of it.

Thanks !

   -- Daniel

>
> Thanks,
>
> Catalin
>
>
>   drivers/clocksource/arm_arch_timer.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index 6a79fc4f900c..095c1774592c 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -462,7 +462,7 @@ static void __init arch_counter_register(unsigned type)
>
>   	/* Register the CP15 based counter if we have one */
>   	if (type & ARCH_CP15_TIMER) {
> -		if (arch_timer_use_virtual)
> +		if (IS_ENABLED(CONFIG_ARM64) || arch_timer_use_virtual)
>   			arch_timer_read_counter = arch_counter_get_cntvct;
>   		else
>   			arch_timer_read_counter = arch_counter_get_cntpct;
>


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