linux-kernel - Re: [PATCH v3 7/8] video: xilinxfb: Fix sparse warnings

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Date:	Fri, 31 May 2013 15:37:53 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Timur Tabi <timur@...i.org>
CC:	Michal Simek <michal.simek@...inx.com>,
	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org
Subject: Re: [PATCH v3 7/8] video: xilinxfb: Fix sparse warnings

On 05/31/2013 03:26 PM, Timur Tabi wrote:
> On 05/31/2013 07:55 AM, Michal Simek wrote:
> 
>> diff --git a/drivers/video/xilinxfb.c b/drivers/video/xilinxfb.c
>> index f3d4a69..e27a4f6 100644
>> --- a/drivers/video/xilinxfb.c
>> +++ b/drivers/video/xilinxfb.c
>> @@ -131,7 +131,7 @@ struct xilinxfb_drvdata {
>>  	dcr_host_t      dcr_host;
>>  	unsigned int    dcr_len;
>>  #endif
>> -	void		*fb_virt;	/* virt. address of the frame buffer */
>> +	void __iomem	*fb_virt;	/* virt. address of the frame buffer */
>>  	dma_addr_t	fb_phys;	/* phys. address of the frame buffer */
>>  	int		fb_alloced;	/* Flag, was the fb memory alloced? */
>>
>> @@ -273,8 +273,10 @@ static int xilinxfb_assign(struct platform_device *pdev,
>>  		drvdata->fb_virt = ioremap(pdata->fb_phys, fbsize);
>>  	} else {
>>  		drvdata->fb_alloced = 1;
>> -		drvdata->fb_virt = dma_alloc_coherent(dev, PAGE_ALIGN(fbsize),
>> -					&drvdata->fb_phys, GFP_KERNEL);
>> +		drvdata->fb_virt = (__force void __iomem *)
>> +				   dma_alloc_coherent(dev, PAGE_ALIGN(fbsize),
>> +						      &drvdata->fb_phys,
>> +						      GFP_KERNEL);
> 
> I think this is wrong.  At least, it would be on PowerPC.
> dma_alloc_coherent() allocates regular RAM, not I/O memory.  So it
> should not be __iomem.

The same is for Microblaze. Driver shares fb_virt for IO memory
and for allocated memory. The purpose of this driver wasn't
to change the driver logic just resolved sparse warnings.
The other way is also wrong.
I have compiled this driver with ppc toolchain and it should
remove sparse warnings for PPC.

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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