[MIPS] time: Make c0_compare_int_usable faster

Try increasingly longer time periods starting of at 0x10 cycles.  This
should be fast on hardware and work nicely with emulators.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c
index 7274fd2513f9..a59f67ff301e 100644
--- a/arch/mips/kernel/cevt-r4k.c
+++ b/arch/mips/kernel/cevt-r4k.c
@@ -179,7 +179,7 @@ static int c0_compare_int_pending(void)
 
 static int c0_compare_int_usable(void)
 {
-        const unsigned int delta = 0x300000;
+        unsigned int delta;
         unsigned int cnt;
 
         /*
@@ -192,9 +192,15 @@ static int c0_compare_int_usable(void)
                         return 0;
         }
 
-        cnt = read_c0_count();
-        cnt += delta;
-        write_c0_compare(cnt);
+        for (delta = 0x10; delta <= 0x400000; delta <<= 1) {
+                cnt = read_c0_count();
+                cnt += delta;
+                write_c0_compare(cnt);
+                irq_disable_hazard();
+                if ((int)(read_c0_count() - cnt) < 0)
+                    break;
+                /* increase delta if the timer was already expired */
+        }
 
         while ((int)(read_c0_count() - cnt) <= 0)
                 ;       /* Wait for expiry  */