[MIPS] Change get_cycles to always return 0.

This avoids us executing an mfc0 c0_count instruction on processors which
don't have but also on certain R4000 and R4400 versions where reading from
the count register just in the very moment when its value equals
c0_compare will result in the timer interrupt getting lost.

There is still a number of users of get_cycles remaining outside the
arch code:

crypto/tcrypt.c:                start = get_cycles();
crypto/tcrypt.c:                end = get_cycles();
crypto/tcrypt.c:                start = get_cycles();
crypto/tcrypt.c:                end = get_cycles();
crypto/tcrypt.c:                start = get_cycles();
crypto/tcrypt.c:                end = get_cycles();
drivers/char/hangcheck-timer.c: return get_cycles();
drivers/char/hangcheck-timer.c: printk("Hangcheck: Using get_cycles().\n");
drivers/char/random.c:  sample.cycles = get_cycles();
drivers/input/joystick/analog.c:#define GET_TIME(x)     do { x = get_cycles(); }
include/linux/arcdevice.h:          _x = get_cycles(); \
include/linux/arcdevice.h:          _y = get_cycles(); \
mm/slub.c:      if (!s->defrag_ratio || get_cycles() % 1024 > s->defrag_ratio)
mm/slub.c:      p += 64 + (get_cycles() & 0xff) * sizeof(void *);

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

diff --git a/include/asm-mips/timex.h b/include/asm-mips/timex.h
index 5816ad1569d66762413fe7cf1748a5ff001ab391..6529704aa73ae0c3cee7789648fb5328b3948168 100644 (file)
--- a/include/asm-mips/timex.h
+++ b/include/asm-mips/timex.h
@@ -35,7 +35,7 @@ typedef unsigned int cycles_t;
 
 static inline cycles_t get_cycles(void)
 {
-       return read_c0_count();
+       return 0;
 }
 
 #endif /* __KERNEL__ */