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

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Message-ID: <20170802045522.GU3053@localhost>
Date:   Wed, 2 Aug 2017 10:25:22 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Pierre Yves MORDRET <pierre-yves.mordret@...com>
Cc:     Peter Ujfalusi <peter.ujfalusi@...com>,
        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 Tue, Aug 01, 2017 at 09:32:50AM +0000, Pierre Yves MORDRET wrote:
> 
> 
> 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.

Yes there is no callback for routers but we can add a generic callback
here to be used. I added Peter for his comments, isn't that something they
need too?

-- 
~Vinod