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

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On 08/02/2017 04:09 PM, Peter Ujfalusi wrote:
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 
> On 2017-08-02 16:11, Pierre Yves MORDRET wrote:
>> Our SoC works with or without DMAMUX. Both binding is allowed. Using only DMA a
>> ChannelId and request line is part of the binding.
> 
> In our case the am335x's eDMA can work with or without the router, we 
> only use the router node if we need none default event for a given DMA 
> request line.
> 
>> Using DMAMUx now the request
>> line is coming from dma_spec forwards to dma-master as well explained by Peter.
>> However ChannelID is now given by dma_get_any_slave_channel instead of bindings.
>> DMAMUX driver has to be aware of this ID to route request line to out DMA
>> channel. This channel id information is carried on until DMAMUX through
>> dmaengine_slave_config with a custom API.
>> Hope it clarifies the need.
> 
> I see, this is not much different then what we face with our dra7 
> devices. In theory we could use direct DMA binding to the DMA controller 
> itself, but some requests would not be reachable, so we always use the 
> router's node for DMA on dra7 family.
> 
> Basically the router would manage the ChannelID and create 
> 'st,stm32-dma' compatible dma_spec (the four parameters).
> Afaik you could have 3 parameters for the router and create a four 
> parameter dma_spec, where the ChannelID is dynamically allocated.

Correct router needs 3 parameters and among those 2 are forwarded though out
dma_spec. But when you say "ChannelID is dynamically allocated" you mean
dma_get_any_slave_channel ? If yes I can use the already existing bindings to
carry the channelID to DMA. No changes need to peripheral...

> But you need to convert all peripherals to use the router's node for the 
> DMA.
> 
> - Péter
> 

Py

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Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Pierre Yves MORDRET <pierre-yves.mordret@st.com> - 2017-08-01 11:40 +0200
  Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Vinod Koul <vinod.koul@intel.com> - 2017-08-02 07:00 +0200
    Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Peter Ujfalusi <peter.ujfalusi@ti.com> - 2017-08-02 11:30 +0200
      Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Pierre Yves MORDRET <pierre-yves.mordret@st.com> - 2017-08-02 15:20 +0200
        Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Peter Ujfalusi <peter.ujfalusi@ti.com> - 2017-08-02 16:20 +0200
          Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Pierre Yves MORDRET <pierre-yves.mordret@st.com> - 2017-08-02 16:30 +0200
            Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Peter Ujfalusi <peter.ujfalusi@ti.com> - 2017-08-03 08:50 +0200
              Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Pierre Yves MORDRET <pierre-yves.mordret@st.com> - 2017-08-03 11:10 +0200
                Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Peter Ujfalusi <peter.ujfalusi@ti.com> - 2017-08-03 12:00 +0200
                Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Pierre Yves MORDRET <pierre-yves.mordret@st.com> - 2017-08-04 15:00 +0200
                Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver Peter Ujfalusi <peter.ujfalusi@ti.com> - 2017-08-04 16:30 +0200

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