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

[Kamal Mostafa]

On Thu, 2015-02-26 at 09:38 -0800, Kamal Mostafa wrote:
> https://launchpad.net/bugs/1426043
> 
> This upstream cherry-pick fixes boot failure on arm64.  The patch has also
> been applied to 3.13-stable.
> 
>  -Kamal
> 
> -----
> 
> From: Catalin Marinas <catalin.marinas at arm.com>
> Date: Wed, 10 Dec 2014 11:02:09 +0000
> Subject: clocksource: arch_timer: Only use the virtual counter (CNTVCT) on arm64
> 
> commit d6ad36913083d683aad4e02e53580c995f1a6ede upstream.
> 
> 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>
> Signed-off-by: Arnd Bergmann <arnd at arndb.de>
> BugLink: https://launchpad.net/bugs/1426043
> Signed-off-by: Kamal Mostafa <kamal at canonical.com>
> ---
>  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 46884f8..a40fc66 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -427,7 +427,7 @@ 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;
> -- 
> 1.9.1
> 
>