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 <cmetcalf@tilera.com>
diff --git a/arch/tile/lib/delay.c b/arch/tile/lib/delay.c
index 5801b03..cdacdd1 100644
--- a/arch/tile/lib/delay.c
+++ b/arch/tile/lib/delay.c
@@ -15,20 +15,31 @@
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/thread_info.h>
-#include <asm/fixmap.h>
-#include <hv/hypervisor.h>
+#include <asm/timex.h>
void __udelay(unsigned long usecs)
{
- hv_nanosleep(usecs * 1000);
+ if (usecs > ULONG_MAX / 1000) {
+ WARN_ON_ONCE(usecs > ULONG_MAX / 1000);
+ usecs = ULONG_MAX / 1000;
+ }
+ __ndelay(usecs * 1000);
}
EXPORT_SYMBOL(__udelay);
void __ndelay(unsigned long nsecs)
{
- hv_nanosleep(nsecs);
+ cycles_t target = get_cycles();
+ target += ns2cycles(nsecs);
+ while (get_cycles() < target)
+ cpu_relax();
}
EXPORT_SYMBOL(__ndelay);
-/* FIXME: should be declared in a header somewhere. */
+void __delay(unsigned long cycles)
+{
+ cycles_t target = get_cycles() + cycles;
+ while (get_cycles() < target)
+ cpu_relax();
+}
EXPORT_SYMBOL(__delay);