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

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Date:	Fri, 31 May 2013 09:39:10 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Michal Simek <michal.simek@...inx.com>,
	linux-kernel@...r.kernel.org,
	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 05/31/2013 12:04 AM, Arnd Bergmann wrote:
> 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.

The PLB_ACCESS_FLAGS is incorrectly named. It means BUS_ACCESS.
But I will find a way how to autodetect endianess directly on IP
as I have done it for uartlite and will send v3.

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform



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