linux-kernel - Re: [spi-devel-general] [PATCH v4] powerpc/5200: Add mpc5200-spi (non-PSC) device driver

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Date:	Fri, 3 Jul 2009 01:01:24 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Wolfram Sang <w.sang@...gutronix.de>
Cc:	linuxppc-dev@...abs.org,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, jonsmirl@...il.com
Subject: Re: [spi-devel-general] [PATCH v4] powerpc/5200: Add mpc5200-spi 
	(non-PSC) device driver

On Thu, Jun 18, 2009 at 8:26 AM, Wolfram Sang<w.sang@...gutronix.de> wrote:
>> There used to be a sysfs interface for dumping these, but it was an
>> ugly misuse.  I'd like to leave these in.  I still have the sysfs bits
>> in a private patch and I'm going to rework them for debugfs.
>
> Okay. Maybe a comment stating the future use will be nice.

okay

>> > But I wonder more about the usage of the SS pin and if this chipsel is needed
>> > at all (sadly I cannot test as I don't have any board with SPI connected to
>> > that device). You define the SS-pin as output, but do not set the SSOE-bit.
>> > More, you use the MODF-feature, so the SS-pin should be defined as input?
>> > According to Table 17.3 in the PM, you have that pin defined as generic purpose
>> > output.
>>
>> That's right.  The SS handling by the SPI device is completely
>> useless, so this driver uses it as a GPIO and asserts it manually.
>
> That definately needs a comment :D (perhaps with some more details if you know them).
>
>> The MODF irq is probably irrelevant, but I'd like to leave it in for
>> completeness.
>
> But it won't work if the pin is set to output, no?

yes

> Are you sure there are no side-effects?

I'm sure.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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