linux-kernel - RE: [patch] split MMC_CAP_4_BIT

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Date:	Wed, 9 Jan 2008 11:21:40 +0800
From:	"Cai, Cliff" <Cliff.Cai@...log.com>
To:	"Pierre Ossman" <drzeus-mmc@...eus.cx>
Cc:	"Mike Frysinger" <vapier.adi@...il.com>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [patch] split MMC_CAP_4_BIT_DATA


 Hi,all

I'd like to say something about this issue.
Currently,the blackfin on chip SD host ONLY support 1-bit MMC while
support 1-bit/4-bit SD/SDIO.
And we want our driver to support both 1-bit MMC and 4-bit SD/SDIO.but
the current MMC driver framework
Only allow us to set one kind of bus width,either 1-bit or 4-bit.So in
order to meet our case,we need more flexible mechanism
To inform the upper commom driver to know our situation.

Cliff

 

-----Original Message-----
From: Bryan Wu [mailto:cooloney.lkml@...il.com] 
Sent: Wednesday, January 09, 2008 10:33 AM
To: Pierre Ossman; cliff.cai@...log.com
Cc: Mike Frysinger; linux-kernel@...r.kernel.org
Subject: Re: [patch] split MMC_CAP_4_BIT_DATA

On Jan 9, 2008 4:49 AM, Pierre Ossman <drzeus-mmc@...eus.cx> wrote:
> On Tue, 8 Jan 2008 14:40:49 -0500
> Mike Frysinger <vapier.adi@...il.com> wrote:
>
> >
> > i dont understand what's confusing.  the Blackfin on chip host 
> > controller only supports 1-bit MMC, but it supports 4-bit SD/SDIO.  
> > this is a fact.  while it may be a stupid decision, it is what it 
> > is, and i need the framework made more flexible in order to get the 
> > Blackfin driver merged cleanly.  we do software for hardware, we
dont do hardware.
>
> Well, since I've seen no _hardware_ differences between 4-bit MMC and
4-bit SD, "support" in this case must me "vendor will guarantee it
works". And that is not the kind of "support" that needs a distinction
in the code.
>
> So, again, if you feel that there is a hardware difference between
4-bit MMC and 4-bit SD then please elaborate as it is my understanding
that they are identical.
>

As Mike said, the reason split this flag is because Blackfin on-chip
SDIO controller's limitation.
Cliff is working on it for a long time, so I dropped him in. Hope he can
clarify the confusing things.

Thanks
-Bryan Wu
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