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From: Conor Dooley <conor@kernel.org>
To: Stephen Boyd <sboyd@kernel.org>
Cc: Jesse Taube <mr.bossman075@gmail.com>,
	linux-riscv@lists.infradead.org, linux-clk@vger.kernel.org,
	linux-kernel@vger.kernel.org, Yimin Gu <ustcymgu@gmail.com>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Waldemar Brodkorb <wbx@openadk.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Conor Dooley <conor.dooley@microchip.com>,
	kernel test robot <lkp@intel.com>
Subject: Re: [PATCH v3 1/3] clk: k210: remove an implicit 64-bit division
Date: Mon, 6 Mar 2023 22:35:01 +0000	[thread overview]
Message-ID: <be589843-dfc1-47dc-a488-a4fad645c638@spud> (raw)
In-Reply-To: <3b0a1481873a2a7c26015fcedcc673b3.sboyd@kernel.org>

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On Mon, Mar 06, 2023 at 02:31:00PM -0800, Stephen Boyd wrote:
> Quoting Jesse Taube (2023-02-28 16:26:55)
> > diff --git a/drivers/clk/clk-k210.c b/drivers/clk/clk-k210.c
> > index 67a7cb3503c3..4eed667eddaf 100644
> > --- a/drivers/clk/clk-k210.c
> > +++ b/drivers/clk/clk-k210.c
> > @@ -495,7 +495,7 @@ static unsigned long k210_pll_get_rate(struct clk_hw *hw,
> >         f = FIELD_GET(K210_PLL_CLKF, reg) + 1;
> >         od = FIELD_GET(K210_PLL_CLKOD, reg) + 1;
> >  
> > -       return (u64)parent_rate * f / (r * od);
> > +       return div_u64((u64)parent_rate * f, r * od);
> 
> The equation 'r * od' can't overflow 32-bits, right?

Yah, I checked that when writing the patch. They're 4-bit fields:
> /*
>  * PLL control register bits.
>  */
> #define K210_PLL_CLKR		GENMASK(3, 0)
> #define K210_PLL_CLKF		GENMASK(9, 4)
> #define K210_PLL_CLKOD		GENMASK(13, 10)

Cheers,
Conor.


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WARNING: multiple messages have this Message-ID (diff)
From: Conor Dooley <conor@kernel.org>
To: Stephen Boyd <sboyd@kernel.org>
Cc: Jesse Taube <mr.bossman075@gmail.com>,
	linux-riscv@lists.infradead.org, linux-clk@vger.kernel.org,
	linux-kernel@vger.kernel.org, Yimin Gu <ustcymgu@gmail.com>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Waldemar Brodkorb <wbx@openadk.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Conor Dooley <conor.dooley@microchip.com>,
	kernel test robot <lkp@intel.com>
Subject: Re: [PATCH v3 1/3] clk: k210: remove an implicit 64-bit division
Date: Mon, 6 Mar 2023 22:35:01 +0000	[thread overview]
Message-ID: <be589843-dfc1-47dc-a488-a4fad645c638@spud> (raw)
In-Reply-To: <3b0a1481873a2a7c26015fcedcc673b3.sboyd@kernel.org>


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On Mon, Mar 06, 2023 at 02:31:00PM -0800, Stephen Boyd wrote:
> Quoting Jesse Taube (2023-02-28 16:26:55)
> > diff --git a/drivers/clk/clk-k210.c b/drivers/clk/clk-k210.c
> > index 67a7cb3503c3..4eed667eddaf 100644
> > --- a/drivers/clk/clk-k210.c
> > +++ b/drivers/clk/clk-k210.c
> > @@ -495,7 +495,7 @@ static unsigned long k210_pll_get_rate(struct clk_hw *hw,
> >         f = FIELD_GET(K210_PLL_CLKF, reg) + 1;
> >         od = FIELD_GET(K210_PLL_CLKOD, reg) + 1;
> >  
> > -       return (u64)parent_rate * f / (r * od);
> > +       return div_u64((u64)parent_rate * f, r * od);
> 
> The equation 'r * od' can't overflow 32-bits, right?

Yah, I checked that when writing the patch. They're 4-bit fields:
> /*
>  * PLL control register bits.
>  */
> #define K210_PLL_CLKR		GENMASK(3, 0)
> #define K210_PLL_CLKF		GENMASK(9, 4)
> #define K210_PLL_CLKOD		GENMASK(13, 10)

Cheers,
Conor.


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  reply	other threads:[~2023-03-06 22:35 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-01  0:26 [PATCH v3 0/3] Add RISC-V 32 NOMMU support Jesse Taube
2023-03-01  0:26 ` Jesse Taube
2023-03-01  0:26 ` [PATCH v3 1/3] clk: k210: remove an implicit 64-bit division Jesse Taube
2023-03-01  0:26   ` Jesse Taube
2023-03-01  1:19   ` Damien Le Moal
2023-03-01  1:19     ` Damien Le Moal
2023-03-06 22:31   ` Stephen Boyd
2023-03-06 22:31     ` Stephen Boyd
2023-03-06 22:35     ` Conor Dooley [this message]
2023-03-06 22:35       ` Conor Dooley
2023-03-06 22:37       ` Stephen Boyd
2023-03-06 22:37         ` Stephen Boyd
2023-03-06 22:41   ` Stephen Boyd
2023-03-06 22:41     ` Stephen Boyd
2023-03-06 22:48     ` Palmer Dabbelt
2023-03-06 22:48       ` Palmer Dabbelt
2023-03-01  0:26 ` [PATCH v3 2/3] riscv: Kconfig: Allow RV32 to build with no MMU Jesse Taube
2023-03-01  0:26   ` Jesse Taube
2023-03-01  1:22   ` Damien Le Moal
2023-03-01  1:22     ` Damien Le Moal
2023-03-01  0:26 ` [PATCH v3 3/3] riscv: configs: Add nommu PHONY defconfig for RV32 Jesse Taube
2023-03-01  0:26   ` Jesse Taube
2023-03-01  4:07 ` [PATCH v3 0/3] Add RISC-V 32 NOMMU support Randy Dunlap
2023-03-01  4:07   ` Randy Dunlap
2023-03-01  4:42   ` Damien Le Moal
2023-03-01  4:42     ` Damien Le Moal
2023-03-08  1:26     ` Jesse Taube
2023-03-08  1:26       ` Jesse Taube
2023-03-08  2:16       ` Randy Dunlap
2023-03-08  2:16         ` Randy Dunlap
2023-03-08  2:30         ` Jesse Taube
2023-03-08  2:30           ` Jesse Taube
2023-03-08  2:33           ` Randy Dunlap
2023-03-08  2:33             ` Randy Dunlap
2023-03-08  2:51             ` Randy Dunlap
2023-03-08  2:51               ` Randy Dunlap
2023-03-08  2:54               ` Jesse Taube
2023-03-08  2:54                 ` Jesse Taube
2023-03-08  3:23                 ` Randy Dunlap
2023-03-08  3:23                   ` Randy Dunlap
2023-03-08  3:42                   ` Damien Le Moal
2023-03-08  3:42                     ` Damien Le Moal
2023-03-08  3:46                     ` Jesse Taube
2023-03-08  3:46                       ` Jesse Taube
2023-03-08  4:11                       ` Damien Le Moal
2023-03-08  4:11                         ` Damien Le Moal
2023-03-14 18:35                         ` Jesse Taube
2023-03-14 18:35                           ` Jesse Taube
2023-03-14 19:16                           ` Conor Dooley
2023-03-14 19:16                             ` Conor Dooley
2023-03-08  3:51                     ` Randy Dunlap
2023-03-08  3:51                       ` Randy Dunlap
2023-03-25 11:57 ` Conor Dooley
2023-03-25 11:57   ` Conor Dooley
2023-03-28 18:50 ` (subset) " Palmer Dabbelt
2023-03-28 18:50   ` Palmer Dabbelt

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