Messages in this thread | | | Date | Mon, 25 Jul 2016 10:02:59 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v8 4/9] clocksource/drivers/arm_arch_timer: use readq to get 64-bit CNTVCT |
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On Wed, Jul 20, 2016 at 02:17:59AM +0800, fu.wei@linaro.org wrote: > From: Fu Wei <fu.wei@linaro.org> > > This patch simplify arch_counter_get_cntvct_mem function by > using readq to get 64-bit CNTVCT value instead of readl_relaxed. > > Signed-off-by: Fu Wei <fu.wei@linaro.org> > --- > drivers/clocksource/arm_arch_timer.c | 10 +--------- > 1 file changed, 1 insertion(+), 9 deletions(-) > > diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c > index e6fd42d..483d2f9 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -418,15 +418,7 @@ u32 arch_timer_get_rate(void) > > static u64 arch_counter_get_cntvct_mem(void) > { > - u32 vct_lo, vct_hi, tmp_hi; > - > - do { > - vct_hi = readl_relaxed(arch_counter_base + CNTVCT_HI); > - vct_lo = readl_relaxed(arch_counter_base + CNTVCT_LO); > - tmp_hi = readl_relaxed(arch_counter_base + CNTVCT_HI); > - } while (vct_hi != tmp_hi); > - > - return ((u64) vct_hi << 32) | vct_lo; > + return readq(arch_counter_base + CNTVCT_LO);
What's the benefit of doing this? If you use readq here, how can we guarantee that (a) the endpoint won't generate a SLVERR or similar and (b) that we get an atomic read?
"If it ain't broke, don't fix it"
Will
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