linux-kernel - Re: [PATCH v2 2/3] video: xilinxfb: Do not use out

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Message-ID: <3808365.SOUxDqkW9J@wuerfel>
Date:	Fri, 31 May 2013 00:04:01 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Michal Simek <michal.simek@...inx.com>
Cc:	linux-kernel@...r.kernel.org, Michal Simek <monstr@...str.eu>,
	Florian Tobias Schandinat <FlorianSchandinat@....de>,
	linux-fbdev@...r.kernel.org
Subject: Re: [PATCH v2 2/3] video: xilinxfb: Do not use out_be32 IO function

On Thursday 30 May 2013 11:41:01 Michal Simek wrote:
>   * To perform the read/write on the registers we need to check on
>   * which bus its connected and call the appropriate write API.
>   */
> -static void xilinx_fb_out_be32(struct xilinxfb_drvdata *drvdata, u32 offset,
> +static void xilinx_fb_out32(struct xilinxfb_drvdata *drvdata, u32 offset,
>                                 u32 val)
>  {
>         if (drvdata->flags & PLB_ACCESS_FLAG)
> -               out_be32(drvdata->regs + (offset << 2), val);
> +               __raw_writel(val, drvdata->regs + (offset << 2));
>  #ifdef CONFIG_PPC_DCR
>         else
>                 dcr_write(drvdata->dcr_host, offset, val);
> 

This is probably missing barriers, and is wrong on systems on which
the endianess of the device is different from the CPU.

You already have an indirection in there, so I guess it won't hurt
to create a third case for little-endian registers and add
another bit in drvdata->flags, or make it depend on the architecture,
if the endianess of the device registers is known at compile time.

	Arnd
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