linux-kernel - Re: [PATCH 1/4] dt-bindings: Document the STM32 DMA bindings

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Message-ID: <CAOAejn0y+6uFbho3iv37xh6=zKevnp_6MxOEw4e9Oc4U2x_csQ@mail.gmail.com>
Date:	Thu, 8 Oct 2015 18:01:23 +0200
From:	"M'boumba Cedric Madianga" <cedric.madianga@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, mcoquelin.stm32@...il.com,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linux@....linux.org.uk, vinod.koul@...el.com,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org
Subject: Re: [PATCH 1/4] dt-bindings: Document the STM32 DMA bindings

Hi Arnd,

2015-10-08 17:43 GMT+02:00 Arnd Bergmann <arnd@...db.de>:
> On Thursday 08 October 2015 17:20:09 M'boumba Cedric Madianga wrote:
>> +Each dmas request consists of 5 cells:
>> +1. A phandle pointing to the STM32 DMA controller
>> +2. The channel id
>> +3. The request line number
>> +4. A 32bit mask specifying the DMA channel configuration
>>
>
> It's fairly unusual to encode the channel id here, rather than
> letting the driver pick one. Is that actually required here?
Yes it is required as in STM32 platform the channel/request DMA
mapping is done by hardware lines.
So, if one client wants to use DMA, he has to choose the correct
channel/request values according to the DMA mapping of his STM32
platform.

>
>         Arnd

 BR,
 Cedric
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