linux-kernel - Re: [PATCH] riscv: Fix udelay in RV32.

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Message-ID: <20190530055258.GA7170@infradead.org>
Date:   Wed, 29 May 2019 22:52:58 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Nick Hu <nickhu@...estech.com>
Cc:     greentime@...estech.com, palmer@...ive.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        green.hu@...il.com
Subject: Re: [PATCH] riscv: Fix udelay in RV32.

On Tue, May 28, 2019 at 05:26:49PM +0800, Nick Hu wrote:
> In RV32, udelay would delay the wrong cycle.
> When it shifts right "UDELAY_SHITFT" bits, it
> either delays 0 cycle or 1 cycle. It only works
> correctly in RV64. Because the 'ucycles' always
> needs to be 64 bits variable.

Please use up all your ~72 chars per line in the commit log.

> diff --git a/arch/riscv/lib/delay.c b/arch/riscv/lib/delay.c
> index dce8ae24c6d3..da847f49fb74 100644
> --- a/arch/riscv/lib/delay.c
> +++ b/arch/riscv/lib/delay.c
> @@ -88,7 +88,7 @@ EXPORT_SYMBOL(__delay);
>  
>  void udelay(unsigned long usecs)
>  {
> -	unsigned long ucycles = usecs * lpj_fine * UDELAY_MULT;
> +	unsigned long long ucycles = (unsigned long long)usecs * lpj_fine * UDELAY_MULT;

And this creates a way too long line.  Pleaase use u64 instead of
unsigned long long to clarify the intention while also fixing the long
lines.