From 13371731487896a6ef158b1cd74297f40a3da4bb Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Mon, 28 Feb 2011 13:21:52 -0500 Subject: arch/tile: fix __ndelay etc to work better The current implementations of __ndelay and __udelay call a hypervisor service to delay, but the hypervisor service isn't actually implemented very well, and the consensus is that Linux should handle figuring this out natively and not use a hypervisor service. By converting nanoseconds to cycles, and then spinning until the cycle counter reaches the desired cycle, we get several benefits: first, we are sensitive to the actual clock speed; second, we use less power by issuing a slow SPR read once every six cycles while we delay; and third, we properly handle the case of an interrupt by exiting at the target time rather than after some number of cycles. Signed-off-by: Chris Metcalf --- arch/tile/kernel/time.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'arch/tile/kernel/time.c') diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c index f2e156e44692..49a605be94c5 100644 --- a/arch/tile/kernel/time.c +++ b/arch/tile/kernel/time.c @@ -224,3 +224,13 @@ int setup_profiling_timer(unsigned int multiplier) { return -EINVAL; } + +/* + * Use the tile timer to convert nsecs to core clock cycles, relying + * on it having the same frequency as SPR_CYCLE. + */ +cycles_t ns2cycles(unsigned long nsecs) +{ + struct clock_event_device *dev = &__get_cpu_var(tile_timer); + return ((u64)nsecs * dev->mult) >> dev->shift; +} -- cgit