linux-kernel - Re: [PATCH] memory: renesas-rpc-if: Avoid unaligned bus access for HyperFlash

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Message-ID: <YU7x8cabSsQiUJuE@kunai>
Date:   Sat, 25 Sep 2021 11:54:57 +0200
From:   Wolfram Sang <wsa@...nel.org>
To:     Andrew Gabbasov <andrew_gabbasov@...tor.com>
Cc:     linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH] memory: renesas-rpc-if: Avoid unaligned bus access for
 HyperFlash

Hi Andrew,

thanks for this patch!

> +	const int maxw = (IS_ENABLED(CONFIG_64BIT)) ? 8 : 4;
> +	u8 buf[2];

I could imagine the code becomes more readable if we make use of
something like:

	unsigned long from_ul = from;

and then use it throughout the function?

> +#ifdef CONFIG_64BIT
> +		*(u64 *)to = __raw_readq(from);
> +#else
> +		*(u32 *)to = __raw_readl(from);
> +#endif

To keep the ifdeffery minimal:

	if (maxw == 8)
		*(u64 *)to = __raw_readq(from);
	else
 		*(u32 *)to = __raw_readl(from);

and let the compiler do its job.

I wondered if this could be a helper function somewhere instead of open
coded in this driver. However, I did not find any similar code in the
kernel yet, so it might be too early to make this a helper. Have you
looked for similar code? I might have just missed it.

Happy hacking,

   Wolfram

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