linux-kernel - Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver

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Message-ID: <e3a76a50-4160-d111-cce9-132b46b66c33@st.com>
Date:   Tue, 1 Aug 2017 09:32:50 +0000
From:   Pierre Yves MORDRET <pierre-yves.mordret@...com>
To:     Vinod Koul <vinod.koul@...el.com>,
        Peter Ujfalusi <peter.ujfalusi@...com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Russell King <linux@...linux.org.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        "M'boumba Cedric Madianga" <cedric.madianga@...il.com>,
        Fabrice GASNIER <fabrice.gasnier@...com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Fabien DESSENNE <fabien.dessenne@...com>,
        Amelie DELAUNAY <amelie.delaunay@...com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver



On 07/31/2017 02:31 PM, Vinod Koul wrote:
> On Wed, Jul 26, 2017 at 07:38:02AM +0000, Pierre Yves MORDRET wrote:
>>>>>> +
>>>>>> +#ifndef __DMA_STM32_DMAMUX_H
>>>>>> +#define __DMA_STM32_DMAMUX_H
>>>>>> +
>>>>>> +#if defined(CONFIG_STM32_DMAMUX)
>>>>>> +int stm32_dmamux_set_config(struct device *dev, void *route_data, u32 chan_id);
>>>>>
>>>>> Why do we need a custom API in this case?
>>>>>
>>>>
>>>> This API is called by DMA when a slave is requested by client. DMA can work
>>>> without DMAMUX this API has been put in place to configure DMAMUX whether client
>>>> is requesting a DMAMUX Channel instead of a DMA one.
>>>
>>> You mean the dmaengine driver right?
>>>
>>
>> Yes. The API is mainly called by "device_config" through out STM32 DMA Driver
>> when a router is in place for client.
>> Please refer to Patch 4/5 on this set.
> 
> Okay am thinking on why this can't be generic..? An optional router config
> callback?
> 

I would have liked to answer there is a callback within engine but unfortunately
I didn't figure out one when I did my router's development. I've looked once
more but again I can't find how to map chanID and request line without custom API.