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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3997f9b5193sm2406841f8f.55.2025.03.21.06.18.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Mar 2025 06:18:17 -0700 (PDT) Date: Fri, 21 Mar 2025 13:18:13 +0000 From: David Laight To: Uwe =?UTF-8?B?S2xlaW5lLUvDtm5pZw==?= Cc: Andrew Morton , Nicolas Pitre , linux-kernel@vger.kernel.org Subject: Re: [PATCH] math64: Provide an uprounding variant of mul_u64_u64_div_u64() Message-ID: <20250321131813.6a332944@pumpkin> In-Reply-To: <20250319171426.175460-2-u.kleine-koenig@baylibre.com> References: <20250319171426.175460-2-u.kleine-koenig@baylibre.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wed, 19 Mar 2025 18:14:25 +0100 Uwe Kleine-K=C3=B6nig wrote: > This is needed (at least) in the pwm-stm32 driver. Currently the > pwm-stm32 driver implements this function itself. This private > implementation can be dropped as a followup of this patch. >=20 > Signed-off-by: Uwe Kleine-K=C3=B6nig > --- > include/linux/math64.h | 1 + > lib/math/div64.c | 15 +++++++++++++++ > 2 files changed, 16 insertions(+) >=20 > diff --git a/include/linux/math64.h b/include/linux/math64.h > index 6aaccc1626ab..0c545b3ddaa5 100644 > --- a/include/linux/math64.h > +++ b/include/linux/math64.h > @@ -283,6 +283,7 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32= divisor) > #endif /* mul_u64_u32_div */ > =20 > u64 mul_u64_u64_div_u64(u64 a, u64 mul, u64 div); > +u64 mul_u64_u64_div_u64_roundup(u64 a, u64 mul, u64 div); > =20 > /** > * DIV64_U64_ROUND_UP - unsigned 64bit divide with 64bit divisor rounded= up > diff --git a/lib/math/div64.c b/lib/math/div64.c > index 5faa29208bdb..66beb669992d 100644 > --- a/lib/math/div64.c > +++ b/lib/math/div64.c > @@ -267,3 +267,18 @@ u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c) > } > EXPORT_SYMBOL(mul_u64_u64_div_u64); > #endif > + > +#ifndef mul_u64_u64_div_u64_roundup > +u64 mul_u64_u64_div_u64_roundup(u64 a, u64 b, u64 c) > +{ > + u64 res =3D mul_u64_u64_div_u64(a, b, c); > + /* Those multiplications might overflow but it doesn't matter */ > + u64 rem =3D a * b - c * res; > + > + if (rem) > + res +=3D 1; Ugg... return (((unsigned __int128_t)a * b) + (c - 1)) / c; nearly works (on 64bit) but needs a u64 div_128_64() David > + > + return res; > +} > +EXPORT_SYMBOL(mul_u64_u64_div_u64_roundup); > +#endif >=20 > base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b