Subject: Re: [PATCH v2] pcmcia: CompactFlash driver for PA Semi Electra boards

From: Milton Miller <[email-masked]>
Date: Wed, 27 Jun 2007 06:20:38 -0500

> On Mon, Jun 25, 2007 at 08:39:09PM +0100, Christoph Hellwig wrote:
>> On Mon, Jun 25, 2007 at 12:12:21PM -0500, Olof Johansson wrote:
>>> Driver for the CompactFlash slot on the PA Semi Electra eval board. 
>>> It's
>>> a simple device sitting on localbus, with interrupts and 
>>> detect/voltage
>>> control over GPIO.
>>>
>>> The driver is implemented as an of_platform driver, and adds localbus
>>> as a bus being probed by the of_platform framework.
>>
>> Looks good to me. The only odd thing is the inconsistant use of
>> #ifdef CONFIG_PCMCIA in setup.c.
>
> The ifdef is needed since for CONFIG_PCMCIA=n builds, the bus notifier
> isn't available. I wanted to do the bus notifier registration 
> explicitly
> before the of_platform bus probe to avoid later surprises due to 
> reordered
> initcalls in case it was split up in it's own initcall.

If CONFIG_PCMCIA=m then your notifier is not registered.  The modprobe 
of your of_driver loads ds.ko, registers the bus, then registers your 
driver.  When the socket driver tries to dma, the BUG in dma_64 for no 
archdata.dma_ops triggers.

It seems like we need

(1) a notifier that a bus is registered, run before allowing any 
devices, so that platforms can register bus notifiers by bus name 
before the devices and drivers are registered.

(2) a powerpc64 generic pcmcia bus notifier that copys the dma ops from 
the parent socket.

(3) something to set the dma_ops to direct_dma_ops on the of device.

If we don't want (3) to be in the driver (as Christoph previosly 
mentioned), then it needs to be a seperate bus that reuses the of 
matching.  This would be similar to how ibmebus is setup.   If I 
remember the discussion, ibmebus is to provide the alternate dma ops 
and steals match etc code from the of_platform bus type.

Oh, is this why you have depends on PCMCIA=y ?

> I could add the code under ifdef as well, but it didn't seem too
> critical. Once the second major board comes along I'll probably move it
> out to a per-board file, there's no real need for it just yet.

milton