From: Andy Shevchenko <andy.shevchenko@gmail.com> To: "Pali Rohár" <pali@kernel.org> Cc: "Geert Uytterhoeven" <geert@linux-m68k.org>, "Michael Turquette" <mturquette@baylibre.com>, "Stephen Boyd" <sboyd@kernel.org>, "Rob Herring" <robh+dt@kernel.org>, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Andrew Lunn" <andrew@lunn.ch>, "Gregory Clement" <gregory.clement@bootlin.com>, "Sebastian Hesselbarth" <sebastian.hesselbarth@gmail.com>, "Vladimir Vid" <vladimir.vid@sartura.hr>, "Marek Behún" <kabel@kernel.org>, linux-clk <linux-clk@vger.kernel.org>, "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Linux ARM" <linux-arm-kernel@lists.infradead.org> Subject: Re: [PATCH v2 07/11] math64: New DIV_U64_ROUND_CLOSEST helper Date: Mon, 19 Jul 2021 15:45:08 +0300 [thread overview] Message-ID: <CAHp75Vdzb9yhm490vAhL7O0S+5FPR=sM1Tohqi70xYV+bXVr8g@mail.gmail.com> (raw) In-Reply-To: <20210625153803.u6uesckcqyvvo7dl@pali> On Fri, Jun 25, 2021 at 6:39 PM Pali Rohár <pali@kernel.org> wrote: > On Friday 25 June 2021 17:22:31 Geert Uytterhoeven wrote: > > On Fri, Jun 25, 2021 at 4:37 PM Pali Rohár <pali@kernel.org> wrote: ... > > > +/* > > > + * DIV_U64_ROUND_CLOSEST - unsigned 64bit divide with 32bit divisor rounded to nearest integer > > > + * @dividend: unsigned 64bit dividend (1) > > > + * @divisor: unsigned 32bit divisor > > > + * > > > + * Divide unsigned 64bit dividend by unsigned 32bit divisor > > > + * and round to closest integer. > > > + * > > > + * Return: dividend / divisor rounded to nearest integer > > > + */ > > > +#define DIV_U64_ROUND_CLOSEST(dividend, divisor) \ > > > + ({ u32 _tmp = (divisor); div_u64((u64)(dividend) + _tmp / 2, _tmp); }) > > > > Given "dividend" should already be an unsigned 64-bit value, I don't > > think the cast to "u64" is needed. Similar macros in this file also > > don't have the cast. > > It is just to ensure that plus operation between dividend and _tmp is > evaluated in 64-bit context to prevent overflow. Just a case when user > calls this macro with 32-bit dividend param. This contradicts (1). > As it is a macro (and not > inline function) type is not automatically enforced. > > DIV_S64_ROUND_CLOSEST macro assigns its argument into temporary 64-bit > variable which then ensures usage of 64-bit arithmetic operations. Same > applies for DIV64_U64_ROUND_CLOSEST and DIV64_U64_ROUND_UP macros. > > So this is reason why I added explicit cast to u64. I don't see the reason for casting in the current code. Probably you need to rephrase documentation to explain why it's there. -- With Best Regards, Andy Shevchenko
WARNING: multiple messages have this Message-ID (diff)
From: Andy Shevchenko <andy.shevchenko@gmail.com> To: "Pali Rohár" <pali@kernel.org> Cc: "Geert Uytterhoeven" <geert@linux-m68k.org>, "Michael Turquette" <mturquette@baylibre.com>, "Stephen Boyd" <sboyd@kernel.org>, "Rob Herring" <robh+dt@kernel.org>, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Andrew Lunn" <andrew@lunn.ch>, "Gregory Clement" <gregory.clement@bootlin.com>, "Sebastian Hesselbarth" <sebastian.hesselbarth@gmail.com>, "Vladimir Vid" <vladimir.vid@sartura.hr>, "Marek Behún" <kabel@kernel.org>, linux-clk <linux-clk@vger.kernel.org>, "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Linux ARM" <linux-arm-kernel@lists.infradead.org> Subject: Re: [PATCH v2 07/11] math64: New DIV_U64_ROUND_CLOSEST helper Date: Mon, 19 Jul 2021 15:45:08 +0300 [thread overview] Message-ID: <CAHp75Vdzb9yhm490vAhL7O0S+5FPR=sM1Tohqi70xYV+bXVr8g@mail.gmail.com> (raw) In-Reply-To: <20210625153803.u6uesckcqyvvo7dl@pali> On Fri, Jun 25, 2021 at 6:39 PM Pali Rohár <pali@kernel.org> wrote: > On Friday 25 June 2021 17:22:31 Geert Uytterhoeven wrote: > > On Fri, Jun 25, 2021 at 4:37 PM Pali Rohár <pali@kernel.org> wrote: ... > > > +/* > > > + * DIV_U64_ROUND_CLOSEST - unsigned 64bit divide with 32bit divisor rounded to nearest integer > > > + * @dividend: unsigned 64bit dividend (1) > > > + * @divisor: unsigned 32bit divisor > > > + * > > > + * Divide unsigned 64bit dividend by unsigned 32bit divisor > > > + * and round to closest integer. > > > + * > > > + * Return: dividend / divisor rounded to nearest integer > > > + */ > > > +#define DIV_U64_ROUND_CLOSEST(dividend, divisor) \ > > > + ({ u32 _tmp = (divisor); div_u64((u64)(dividend) + _tmp / 2, _tmp); }) > > > > Given "dividend" should already be an unsigned 64-bit value, I don't > > think the cast to "u64" is needed. Similar macros in this file also > > don't have the cast. > > It is just to ensure that plus operation between dividend and _tmp is > evaluated in 64-bit context to prevent overflow. Just a case when user > calls this macro with 32-bit dividend param. This contradicts (1). > As it is a macro (and not > inline function) type is not automatically enforced. > > DIV_S64_ROUND_CLOSEST macro assigns its argument into temporary 64-bit > variable which then ensures usage of 64-bit arithmetic operations. Same > applies for DIV64_U64_ROUND_CLOSEST and DIV64_U64_ROUND_UP macros. > > So this is reason why I added explicit cast to u64. I don't see the reason for casting in the current code. Probably you need to rephrase documentation to explain why it's there. -- With Best Regards, Andy Shevchenko _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-07-19 12:45 UTC|newest] Thread overview: 152+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-24 22:48 [PATCH 00/10] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár 2021-06-24 22:48 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 01/10] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 02/10] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 03/10] serial: mvebu-uart: correctly calculate minimal possible baudrate Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 04/10] dt-bindings: mvebu-uart: fix documentation Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 05/10] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 06/10] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 07/10] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-25 5:36 ` kernel test robot 2021-06-25 5:36 ` kernel test robot 2021-06-25 8:15 ` kernel test robot 2021-06-25 8:15 ` kernel test robot 2021-06-25 9:31 ` Pali Rohár 2021-06-25 9:31 ` Pali Rohár 2021-06-25 11:05 ` Geert Uytterhoeven 2021-06-25 11:05 ` Geert Uytterhoeven 2021-06-25 11:29 ` Pali Rohár 2021-06-25 11:29 ` Pali Rohár 2021-06-25 12:44 ` Geert Uytterhoeven 2021-06-25 12:44 ` Geert Uytterhoeven 2021-06-25 13:22 ` Pali Rohár 2021-06-25 13:22 ` Pali Rohár 2021-06-25 13:35 ` Geert Uytterhoeven 2021-06-25 13:35 ` Geert Uytterhoeven 2021-06-25 14:09 ` Pali Rohár 2021-06-25 14:09 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 08/10] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár 2021-06-24 22:49 ` [PATCH 08/10] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Pali Rohár 2021-06-24 22:49 ` [PATCH 09/10] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-24 22:49 ` [PATCH 10/10] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár 2021-06-24 22:49 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 00/11] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 01/11] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 02/11] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 03/11] serial: mvebu-uart: correctly calculate minimal possible baudrate Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 04/11] dt-bindings: mvebu-uart: fix documentation Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 05/11] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 06/11] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 07/11] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 15:22 ` Geert Uytterhoeven 2021-06-25 15:22 ` Geert Uytterhoeven 2021-06-25 15:38 ` Pali Rohár 2021-06-25 15:38 ` Pali Rohár 2021-06-25 15:50 ` Willy Tarreau 2021-06-25 15:50 ` Willy Tarreau 2021-06-25 17:39 ` Geert Uytterhoeven 2021-06-25 17:39 ` Geert Uytterhoeven 2021-06-25 17:44 ` Pali Rohár 2021-06-25 17:44 ` Pali Rohár 2021-06-25 18:11 ` Geert Uytterhoeven 2021-06-25 18:11 ` Geert Uytterhoeven 2021-07-19 12:45 ` Andy Shevchenko [this message] 2021-07-19 12:45 ` Andy Shevchenko 2021-06-25 14:36 ` [PATCH v2 08/11] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 09/11] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár 2021-06-25 14:36 ` [PATCH v2 09/11] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Pali Rohár 2021-06-25 14:36 ` [PATCH v2 10/11] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-06-25 14:36 ` [PATCH v2 11/11] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár 2021-06-25 14:36 ` Pali Rohár 2021-07-17 12:38 ` [PATCH v3 0/5] serial: mvebu-uart: Support for higher baudrates Pali Rohár 2021-07-17 12:38 ` Pali Rohár 2021-07-17 12:38 ` [PATCH v3 1/5] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár 2021-07-17 12:38 ` Pali Rohár 2021-07-19 12:47 ` Andy Shevchenko 2021-07-19 12:47 ` Andy Shevchenko 2021-07-22 21:57 ` Pali Rohár 2021-07-22 21:57 ` Pali Rohár 2021-07-24 11:38 ` David Laight 2021-07-24 11:38 ` David Laight 2021-07-17 12:38 ` [PATCH v3 2/5] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár 2021-07-17 12:38 ` Pali Rohár 2021-07-17 17:26 ` Andrew Lunn 2021-07-17 17:26 ` Andrew Lunn 2021-07-17 18:05 ` Pali Rohár 2021-07-17 18:05 ` Pali Rohár 2021-07-24 9:48 ` Pali Rohár 2021-07-24 9:48 ` Pali Rohár 2021-07-24 16:33 ` Andrew Lunn 2021-07-24 16:33 ` Andrew Lunn 2021-07-25 12:14 ` Pali Rohár 2021-07-25 12:14 ` Pali Rohár 2021-07-17 12:38 ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár 2021-07-17 12:38 ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Pali Rohár 2021-07-17 17:30 ` Andrew Lunn 2021-07-17 17:30 ` Andrew Lunn 2021-08-02 14:45 ` Pali Rohár 2021-08-02 14:45 ` Pali Rohár 2021-07-17 12:38 ` [PATCH v3 4/5] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár 2021-07-17 12:38 ` Pali Rohár 2021-07-17 12:38 ` [PATCH v3 5/5] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár 2021-07-17 12:38 ` Pali Rohár 2021-08-02 14:45 ` [PATCH v4 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár 2021-08-02 14:45 ` Pali Rohár 2021-08-02 14:45 ` [PATCH v4 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár 2021-08-02 14:45 ` Pali Rohár 2021-08-02 14:45 ` [PATCH v4 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár 2021-08-02 14:45 ` Pali Rohár 2021-08-02 14:45 ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár 2021-08-02 14:45 ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Pali Rohár 2021-08-06 0:30 ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Stephen Boyd 2021-08-06 0:30 ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Stephen Boyd 2021-08-06 8:28 ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár 2021-08-06 8:28 ` Pali Rohár 2021-08-12 19:33 ` Stephen Boyd 2021-08-12 19:33 ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Stephen Boyd 2021-08-12 20:08 ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár 2021-08-12 20:08 ` Pali Rohár 2021-08-02 14:45 ` [PATCH v4 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár 2021-08-02 14:45 ` Pali Rohár 2021-08-02 14:45 ` [PATCH v4 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár 2021-08-02 14:45 ` Pali Rohár 2021-08-02 14:45 ` [PATCH v4 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár 2021-08-02 14:45 ` Pali Rohár 2021-08-09 14:53 ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár 2021-08-09 14:53 ` Pali Rohár 2021-08-09 14:53 ` [PATCH v5 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár 2021-08-09 14:53 ` Pali Rohár 2021-08-09 14:53 ` [PATCH v5 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár 2021-08-09 14:53 ` Pali Rohár 2021-08-09 14:53 ` [PATCH v5 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár 2021-08-09 14:53 ` [PATCH v5 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Pali Rohár 2021-08-09 14:53 ` [PATCH v5 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár 2021-08-09 14:53 ` Pali Rohár 2021-08-09 14:53 ` [PATCH v5 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár 2021-08-09 14:53 ` Pali Rohár 2021-08-09 14:53 ` [PATCH v5 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár 2021-08-09 14:53 ` Pali Rohár 2021-08-20 17:22 ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár 2021-08-20 17:22 ` Pali Rohár 2021-08-31 8:35 ` Pali Rohár 2021-08-31 8:35 ` Pali Rohár 2021-09-21 7:41 ` Greg Kroah-Hartman 2021-09-21 7:41 ` Greg Kroah-Hartman
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