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authorChris Metcalf <cmetcalf@tilera.com>2011-02-28 13:21:52 -0500
committerChris Metcalf <cmetcalf@tilera.com>2011-03-01 16:20:04 -0500
commit13371731487896a6ef158b1cd74297f40a3da4bb (patch)
treeaf09fca3fd8811340b373faaddcdb528f8a07669 /arch/tile/lib
parent04f7a3f12e10032ee3d44df1a509dbf5b2001fce (diff)
downloadop-kernel-dev-13371731487896a6ef158b1cd74297f40a3da4bb.zip
op-kernel-dev-13371731487896a6ef158b1cd74297f40a3da4bb.tar.gz
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>
Diffstat (limited to 'arch/tile/lib')
-rw-r--r--arch/tile/lib/delay.c21
1 files changed, 16 insertions, 5 deletions
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);
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