[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>

diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c
index 7274fd2..a59f67f 100644 (file)
--- 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  */