linux-kernel - Re: [PATCH v3 1/3] clk: k210: remove an implicit 64-bit division

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Message-ID: <3b0a1481873a2a7c26015fcedcc673b3.sboyd@kernel.org>
Date:   Mon, 06 Mar 2023 14:31:00 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jesse Taube <mr.bossman075@...il.com>,
        linux-riscv@...ts.infradead.org
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jesse Taube <Mr.Bossman075@...il.com>,
        Yimin Gu <ustcymgu@...il.com>,
        Damien Le Moal <damien.lemoal@....com>,
        Michael Turquette <mturquette@...libre.com>,
        Waldemar Brodkorb <wbx@...nadk.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3 1/3] clk: k210: remove an implicit 64-bit division

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?