Commit 196bffa5 authored Jul 21, 2007 by Mark Fortescue Committed by David S. Miller Jul 21, 2007

[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>

parent c2e68052

arch/sparc/kernel/entry.S

+10 −4

Original line number	Diff line number	Diff line
		@@ -1749,8 +1749,8 @@ fpload:
		__ndelay:
		save %sp, -STACKFRAME_SZ, %sp
		mov %i0, %o0
		call .umul
		mov 0x1ad, %o1 ! 2**32 / (1 000 000 000 / HZ)
		call .umul ! round multiplier up so large ns ok
		mov 0x1ae, %o1 ! 2**32 / (1 000 000 000 / HZ)
		call .umul
		mov %i1, %o1 ! udelay_val
		ba delay_continue
		@@ -1760,11 +1760,17 @@ __ndelay:
		__udelay:
		save %sp, -STACKFRAME_SZ, %sp
		mov %i0, %o0
		sethi %hi(0x10c6), %o1
		sethi %hi(0x10c7), %o1 ! round multiplier up so large us ok
		call .umul
		or %o1, %lo(0x10c6), %o1 ! 2**32 / 1 000 000
		or %o1, %lo(0x10c7), %o1 ! 2**32 / 1 000 000
		call .umul
		mov %i1, %o1 ! udelay_val
		sethi %hi(0x028f4b62), %l0 ! Add in rounding constant * 2**32,
		or %g0, %lo(0x028f4b62), %l0
		addcc %o0, %l0, %o0 ! 2*32 0.009 999
		bcs,a 3f
		add %o1, 0x01, %o1
		3:
		call .umul
		mov HZ, %o0 ! >>32 earlier for wider range