sh: Ensure ST40-300 BogoMIPS value is consistent
Stuart Menefy [Thu, 11 Nov 2010 18:26:31 +0000 (18:26 +0000)]
A strange variation was seen in the BogoMIPS figure for the ST40-300.
This was eventually tracked down to sensitivity to the alignment of
the loop. So add an align directive to ensure this doesn't occur.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/lib/delay.c

index faa8f86..0901b2f 100644 (file)
 void __delay(unsigned long loops)
 {
        __asm__ __volatile__(
+               /*
+                * ST40-300 appears to have an issue with this code,
+                * normally taking two cycles each loop, as with all
+                * other SH variants. If however the branch and the
+                * delay slot straddle an 8 byte boundary, this increases
+                * to 3 cycles.
+                * This align directive ensures this doesn't occur.
+                */
+               ".balign 8\n\t"
+
                "tst    %0, %0\n\t"
                "1:\t"
                "bf/s   1b\n\t"