Date: Fri, 18 Aug 2023 01:21:25 GMT From: "Bjoern A. Zeeb" <bz@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: b80ea452375f - main - LinuxKPI: implement mul_u64_u64_div_u64() Message-ID: <202308180121.37I1LPTc024071@gitrepo.freebsd.org>
next in thread | raw e-mail | index | archive | help
The branch main has been updated by bz: URL: https://cgit.FreeBSD.org/src/commit/?id=b80ea452375f52a3ab7d82a9aef10da0d89985d9 commit b80ea452375f52a3ab7d82a9aef10da0d89985d9 Author: Bjoern A. Zeeb <bz@FreeBSD.org> AuthorDate: 2023-05-16 20:55:00 +0000 Commit: Bjoern A. Zeeb <bz@FreeBSD.org> CommitDate: 2023-08-18 01:20:39 +0000 LinuxKPI: implement mul_u64_u64_div_u64() 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 --- sys/compat/linuxkpi/common/include/linux/math64.h | 48 +++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/sys/compat/linuxkpi/common/include/linux/math64.h b/sys/compat/linuxkpi/common/include/linux/math64.h index 1b00fd71e69f..e4ddce5b823e 100644 --- a/sys/compat/linuxkpi/common/include/linux/math64.h +++ b/sys/compat/linuxkpi/common/include/linux/math64.h @@ -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) {
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202308180121.37I1LPTc024071>