Subject: [PATCH] clocksource: arch_timer: Allow the device tree to specify the physical timer

From: [email-masked] (Will Deacon)
Date: Thu, 11 Sep 2014 17:09:08 +0100

On Thu, Sep 11, 2014 at 05:04:11PM +0100, Doug Anderson wrote:
> On Thu, Sep 11, 2014 at 8:58 AM, Christopher Covington
> <[email-masked]> wrote:
> > On 09/11/2014 11:52 AM, Doug Anderson wrote:
> >> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> >> index 5163ec1..8ca07a9 100644
> >> --- a/drivers/clocksource/arm_arch_timer.c
> >> +++ b/drivers/clocksource/arm_arch_timer.c
> >> @@ -649,6 +649,9 @@ static void __init arch_timer_init(struct device_node *np)
> >>               arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
> >>       arch_timer_detect_rate(NULL, np);
> >>
> >> +     if (of_property_read_bool(np, "arm,use-physical-timer"))
> >> +             arch_timer_use_virtual = false;

Can you #ifdef CONFIG_ARM here please?

> >>       /*
> >>        * If HYP mode is available, we know that the physical timer
> >>        * has been configured to be accessible from PL1. Use it, so
> >>
> >
> > How's the VDSO supposed to deal with this? It currently does:
> >
> > cycle_now = arch_counter_get_cntvct()
> 
> I don't see that line of code anywhere when I do a "git grep" on linux
> or linuxnext.  Can you give me a clearer pointer?

It's in the actual vdso code (arch/arm64/kernel/vdso/gettimeofday.S):

	/* Read the virtual counter. */
	isb
	mrs	x15, cntvct_el0

Will