linux-kernel - Re: [PATCH] spi/pl022: Devicetree support w/o platform data

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Message-ID: <50587C98.7040103@antcom.de>
Date:	Tue, 18 Sep 2012 15:52:24 +0200
From:	Roland Stigge <stigge@...com.de>
To:	Arnd Bergmann <arnd@...db.de>
CC:	broonie@...nsource.wolfsonmicro.com, grant.likely@...retlab.ca,
	linus.walleij@...aro.org, lee.jones@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	STEricsson_nomadik_linux@...t.st.com,
	devicetree-discuss@...ts.ozlabs.org, aletes.xgr@...il.com,
	kevin.wells@....com, srinivas.bakki@....com
Subject: Re: [PATCH] spi/pl022: Devicetree support w/o platform data

Hi!

On 09/18/2012 03:13 PM, Arnd Bergmann wrote:
> On Tuesday 18 September 2012, Roland Stigge wrote:
>> --- linux-2.6.orig/Documentation/devicetree/bindings/spi/spi_pl022.txt
>> +++ linux-2.6/Documentation/devicetree/bindings/spi/spi_pl022.txt
>> @@ -10,6 +10,15 @@ Optional properties:
>>  - cs-gpios : should specify GPIOs used for chipselects.
>>    The gpios will be referred to as reg = <index> in the SPI child nodes.
>>    If unspecified, a single SPI device without a chip select can be used.
>> +- pl022,bus-id : Bus ID (0, 1, ...)
> 
> I don't understand why we need the bus-id here. My understanding is that
> this is a linux-specific number that should not be necessary when all
> devices are described in the device tree rather than through spi_board_info.
> 
> Can't you just set master->bus_num to -1 when using the DT for probing?
> 
>> +- pl022,enable-dma : enables DMA driven transfers (boolean)
> 
> Similar thing here: Can't you just set the enable_dma flag when
> a dma channel is provided in the device tree and unset it otherwise?
> 
> It also seems a bit pointless to enable DMA mode when you don't provide
> a way to specify the channel at the same time.

Completely right! I'm removing pl022,bus-id, setting bus_id to -1 in the
dt case. And removing pl022,enable-dma since dma is anyway only useful
in the platform data case where the dma_filter() callback is specified.

Thanks for pointing this out,

Roland
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