From: Grant Likely <grant.likely@secretlab.ca>
To: avorontsov@ru.mvista.com
Cc: Torsten Fleischer <to-fleischer@t-online.de>,
spi-devel-general@lists.sourceforge.net,
linuxppc-dev@lists.ozlabs.org
Subject: Re: spi_mpc8xxx.c: chip select polarity problem
Date: Thu, 26 Nov 2009 12:17:35 -0700 [thread overview]
Message-ID: <fa686aa40911261117y4744e56bmf4d1d8260c7a51d0@mail.gmail.com> (raw)
In-Reply-To: <20091126190101.GA19404@oksana.dev.rtsoft.ru>
On Thu, Nov 26, 2009 at 12:01 PM, Anton Vorontsov
<avorontsov@ru.mvista.com> wrote:
> On Thu, Nov 26, 2009 at 11:50:05AM -0700, Grant Likely wrote:
>> On Thu, Nov 26, 2009 at 11:41 AM, Anton Vorontsov
>> <avorontsov@ru.mvista.com> wrote:
>> > On Thu, Nov 26, 2009 at 11:16:34AM -0700, Grant Likely wrote:
>> > [...]
>> >> The spi-cs-high property is defined in
>> >> Documentation/powerpc/dts-bindings/spi-bus.txt, but it definitely was
>> >> a mistake
>> >
>> > Yup.
>> >
>> >> Currently the spi-cs-high property is parsed in the
>> >> of_register_spi_devices() function, but the CS polarity needs to be
>> >> known before registering devices. It needs to be factored out into
>> >> another utility function callable by spi bus drivers so that it can
>> >> get polarity data at probe time.
>> >
>> > Untill we have this, Torsten's patch is a real improvement, and
>> > works for non-broken hw/fw.
>> >
>> > So I think it should be applied.
>>
>> I disagree since it only band-aids the problem and uglifies the driver
>> in the process. In the immediate term the driver needs to be changed
>> to read the spi-cs-high property out of the child nodes before
>> registering the devices.
>
> Hm. I thought we agreed that spi-cs-high is not good? Why do you
> encourage using it then? We'll have to uglify the driver with
> legacy device-tree handling code.
spi-cs-high is definitely not a complete solution, but it isn't
actively evil either. Plus it is documented and (presumably) in
active use. so support for it should not be dropped.
Regardless, there needs to be a library function for parsing all the
SPI child nodes and returning the active state for each GPIO chip
select. All the code for parsing the old spi-cs-high properties can
be contained in the same place as a new yet-to-be-defined bus node cs
polarity property. The rework to the driver itself is not ugly.
g.
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
prev parent reply other threads:[~2009-11-26 19:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200911161742.46663.to-fleischer@t-online.de>
[not found] ` <200911211708.47253.to-fleischer@t-online.de>
[not found] ` <fa686aa40911241633q38dc0cf8x8b23038fe2fdf10d@mail.gmail.com>
[not found] ` <200911252141.59549.to-fleischer@t-online.de>
2009-11-25 22:11 ` spi_mpc8xxx.c: chip select polarity problem Grant Likely
2009-11-26 12:12 ` Anton Vorontsov
2009-11-26 17:27 ` Torsten Fleischer
2009-11-26 18:18 ` Grant Likely
2009-11-26 18:16 ` Grant Likely
2009-11-26 18:41 ` Anton Vorontsov
2009-11-26 18:50 ` Grant Likely
2009-11-26 19:01 ` Anton Vorontsov
2009-11-26 19:17 ` Grant Likely [this message]
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