linux-kernel - Re: [PATCH 6/13] devres: implement managed iomap interface

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Date:	Thu, 10 Apr 2008 22:24:54 +0400
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Kumar Gala <galak@...nel.crashing.org>
Cc:	Tejun Heo <htejun@...il.com>, linux-ide@...r.kernel.org,
	gregkh@...e.de, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org, jgarzik@...ox.com,
	alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH 6/13] devres: implement managed iomap interface

Kumar Gala wrote:

>>>>>   Those functions are going to break on 32-bit platforms with  
>>>>> extended physical address (well, that's starting with Pentiums  
>>>>> which had 36-bit PAE :-) AND devices mapped beyond 4 GB (e.g.  
>>>>> PowerPC 44x).  You should have used resource_size_t for the  
>>>>> 'offset' parameter. As this most probably means that libata is  
>>>>> broken on such platforms, I'm going to submit a patch...

>>>   It's broken with drivers using MMIO, I meant to say.

>>   Oops, I meant PCI drivers here, at least for the time being. And  it 
>> looks like that was a false alarm. :-]

>>>> Yeah, right please go ahead.  But I wonder whether any BIOS was  
>>>> actually crazy enough to map mmio region above 4G on 32bit machine.

>>>   This is a *hardware* mapping on some non-x86 platforms (like PPC  
>>> 44x or MIPS Alchemy). The arch/ppc/ and arch/mips/ kernels have  
>>> special hooks called from ioremap() which help create an illusion  
>>> that the PCI memory space on such platforms (not only it) is mapped  
>>> below 4 GB; arch/powerpc/ kernel doesn't do this anymore -- hence  
>>> this newly encountered issue.

>>   I thought that pcim_iomap() used devm_ioremap() or something --  
>> which of course turned to be wrong. devm_ioremap() alone is yet safe  
>> since there are no users for it amongst PPC 44x platform device  
>> drivers...

> but there is no reason not to make it work properly.  For example I  
> believe libata uses devm_* and the fsl SATA driver (non-PCI) will need  
> to work in cases similar to the 44x.

    Well, as for sata_fsl, it calls of_iomap() which does The Right Thing.

> - k

WBR, Sergei
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