linux-kernel - Re: [PATCH 1/6] rapidio: add common mapping APIs for RapidIO memory access

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Message-Id: <5D8775BD-9973-4DE8-B442-91FB15F86ACC@kernel.crashing.org>
Date:	Thu, 11 Jun 2009 08:32:24 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Li Yang-R58472 <LeoLi@...escale.com>
Cc:	<akpm@...ux-foundation.org>, <davem@...emloft.net>,
	<mporter@...nel.crashing.org>, <linux-kernel@...r.kernel.org>,
	<linuxppc-dev@...abs.org>, <netdev@...r.kernel.org>,
	"Zhang Wei" <zw@...kernel.org>
Subject: Re: [PATCH 1/6] rapidio: add common mapping APIs for RapidIO memory access


On Jun 11, 2009, at 4:47 AM, Li Yang-R58472 wrote:

>> On May 12, 2009, at 3:35 AM, Li Yang wrote:
>>
>>> Add the mapping functions used to support direct IO memory access of
>>> rapidIO.
>>>
>>> Signed-off-by: Zhang Wei <zw@...kernel.org>
>>> Signed-off-by: Li Yang <leoli@...escale.com>
>>
>> Use inbnd/outbnd instead of inb/outb which make one think of
>> byte level io accessors.
>>
>> As I look at this I don't think this is the correct API.  I
>> think we should be using the DMA mapping API to hide these
>> details.  The concept of mapping like this seems to be more a
>> function of FSL's Address translation/mapping unit (ATMU) than
>> anything specific to the RIO bus standard.
>
> This is a separate RIO block level ATMU.  Although it looks like the
> system level ATMU, system ATMU doesn't have the knowledge of rapidIO
> target device ID.  The mapping need to be dynamic, as it's easy to  
> have
> more RIO devices than the outbound windows.

I understand that.  What I'm saying is the RIO block level ATMU is a  
Freescale specific detail and not part of any standard RIO bus  
programming model.  We have mapping APIs that we can connect to for  
this via the DMA API layer.

- k
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