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authorMark Fortescue <mark@mtfhpc.demon.co.uk>2007-07-21 22:17:41 -0400
committerDavid S. Miller <davem@davemloft.net>2007-07-21 22:17:41 -0400
commit196bffa5dc3181897bd32e41415ec0db8dbab5e7 (patch)
tree24675b94165ea6886827d47006cb12e9dd6b3539
parentc2e68052429fdf87702fccd272951282bef1c60a (diff)
[SPARC32]: Fix rounding errors in ndelay/udelay implementation.
__ndelay and __udelay have not been delayung >= specified time. The problem with __ndelay has been tacked down to the rounding of the multiplier constant. By changing this, delays > app 18us are correctly calculated. The problem with __udelay has also been tracked down to rounding issues. Changing the multiplier constant (to match that used in sparc64) corrects for large delays and adding in a rounding constant corrects for trunctaion errors in the claculations. Many short delays will return without looping. This is not an error as there is the fixed delay of doing all the maths to calculate the loop count. Signed-off-by: Mark Fortescue <mark@mtfhpc.demon.co.uk> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--arch/sparc/kernel/entry.S14
1 files changed, 10 insertions, 4 deletions
diff --git a/arch/sparc/kernel/entry.S b/arch/sparc/kernel/entry.S
index 831f540251f8..eac38388f5fd 100644
--- a/arch/sparc/kernel/entry.S
+++ b/arch/sparc/kernel/entry.S
@@ -1749,8 +1749,8 @@ fpload:
1749__ndelay: 1749__ndelay:
1750 save %sp, -STACKFRAME_SZ, %sp 1750 save %sp, -STACKFRAME_SZ, %sp
1751 mov %i0, %o0 1751 mov %i0, %o0
1752 call .umul 1752 call .umul ! round multiplier up so large ns ok
1753 mov 0x1ad, %o1 ! 2**32 / (1 000 000 000 / HZ) 1753 mov 0x1ae, %o1 ! 2**32 / (1 000 000 000 / HZ)
1754 call .umul 1754 call .umul
1755 mov %i1, %o1 ! udelay_val 1755 mov %i1, %o1 ! udelay_val
1756 ba delay_continue 1756 ba delay_continue
@@ -1760,11 +1760,17 @@ __ndelay:
1760__udelay: 1760__udelay:
1761 save %sp, -STACKFRAME_SZ, %sp 1761 save %sp, -STACKFRAME_SZ, %sp
1762 mov %i0, %o0 1762 mov %i0, %o0
1763 sethi %hi(0x10c6), %o1 1763 sethi %hi(0x10c7), %o1 ! round multiplier up so large us ok
1764 call .umul 1764 call .umul
1765 or %o1, %lo(0x10c6), %o1 ! 2**32 / 1 000 000 1765 or %o1, %lo(0x10c7), %o1 ! 2**32 / 1 000 000
1766 call .umul 1766 call .umul
1767 mov %i1, %o1 ! udelay_val 1767 mov %i1, %o1 ! udelay_val
1768 sethi %hi(0x028f4b62), %l0 ! Add in rounding constant * 2**32,
1769 or %g0, %lo(0x028f4b62), %l0
1770 addcc %o0, %l0, %o0 ! 2**32 * 0.009 999
1771 bcs,a 3f
1772 add %o1, 0x01, %o1
17733:
1768 call .umul 1774 call .umul
1769 mov HZ, %o0 ! >>32 earlier for wider range 1775 mov HZ, %o0 ! >>32 earlier for wider range
1770 1776