d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

LinuxKPI: implement mul_u64_u64_div_u64()

Browse Source 
Implement mul_u64_u64_div_u64() for an updated iwlwifi driver (though
we do not yet use it there; it is used for in-kernel ptp on wifi).

Sponsored by:	The FreeBSD Foundation
Submitted by:	cperciva
MFC after:	10 days
Reviewed by:	cperciva, dwmalone
Differential Revision: https://reviews.freebsd.org/D40120
This commit is contained in:
Bjoern A. Zeeb 2023-05-16 20:55:00 +00:00
parent 98fd1add67
commit b80ea45237
1 changed files with 48 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
sys/compat/linuxkpi/common/include/linux/math64.h
View File

@ -106,6 +106,54 @@ mul_u64_u32_div(uint64_t x, uint32_t y, uint32_t div)
return ((x / div) * y + (rem * y) / div);
}
static inline uint64_t
mul_u64_u64_div_u64(uint64_t x, uint64_t y, uint64_t z)
{
uint64_t res, rem;
uint64_t x1, y1, y1z;
res = rem = 0;
x1 = x;
y1z = y / z;
y1 = y - y1z * z;
/*
* INVARIANT: x * y = res * z + rem + (y1 + y1z * z) * x1
* INVARIANT: y1 < z
* INVARIANT: rem < z
*/
while (x1 > 0) {
/* Handle low bit. */
if (x1 & 1) {
x1 &= ~1;
res += y1z;
rem += y1;
if ((rem < y1) || (rem >= z)) {
res += 1;
rem -= z;
}
}
/* Shift x1 right and (y1 + y1z * z) left */
x1 >>= 1;
if ((y1 * 2 < y1) || (y1 * 2 >= z)) {
y1z = y1z * 2 + 1;
y1 = y1 * 2 - z;
} else {
y1z *= 2;
y1 *= 2;
}
}
KASSERT(res * z + rem == x * y, ("%s: res %ju * z %ju + rem %ju != "
"x %ju * y %ju", __func__, (uintmax_t)res, (uintmax_t)z,
(uintmax_t)rem, (uintmax_t)x, (uintmax_t)y));
KASSERT(rem < z, ("%s: rem %ju >= z %ju\n", __func__,
(uintmax_t)rem, (uintmax_t)z);
return (res);
}
static inline uint64_t
mul_u64_u32_shr(uint64_t x, uint32_t y, unsigned int shift)
{