linux-kernel - Re: [PATCH v2 0/7] Add-DMA-MDMA-chaining-support

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Date:   Fri, 28 Sep 2018 16:30:51 +0200
From:   Pierre Yves MORDRET <pierre-yves.mordret@...com>
To:     Vinod Koul <vkoul@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        <devicetree@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/7] Add-DMA-MDMA-chaining-support

Hello all,

I've submitted a V3 following a KBuild warning.
You can thus drop this V2.

Thanks and sorry for the spamming.

Have a nice weekend.
Regards

On 09/28/2018 10:36 AM, Pierre-Yves MORDRET wrote:
> This serie adds support for M2M transfer triggered by STM32 DMA in order to
> transfer data from/to SRAM to/from DDR.
> 
> Normally, this mode should not be needed as transferring data from/to DDR
> is supported by the STM32 DMA.
> However, the STM32 DMA don't have the ability to generate burst transfer
> on the DDR as it only embeds only a 4-word FIFO although the minimal burst
> length on the DDR is 8 words.
> Due to this constraint, the STM32 DMA transfers data from/to DDR in a
> single way and could lead to pollute the DDR.
> To avoid this, we have to use SRAM for all transfers where STM32 DMA is
> involved.
> 
> An Hw design has been specially put in place to allow this chaining where DMA
> interrupt is connected on GIC and MDMA request line as well. This grants the
> possibility to trigger an MDMA transfer from the completion of DMA.
> At the same time MDMA has the ability to acknowlege DMA. The aim is to have an
> self refreching mechanism to transfer from/to device to/from DDR with minimal
> sw support.
> For instance the DMA is set in cyclic double buffering to feed SRAM and MDMA
> transfer to DDR thanks to LLI.
> 
> M'boumba Cedric Madianga (7):
>   dt-bindings: stm32-dma: Add DMA/MDMA chaining support bindings
>   dt-bindings: stm32-dmamux: Add one cell to support DMA/MDMA chain
>   dt-bindings: stm32-mdma: Add DMA/MDMA chaining support bindings
>   dmaengine: stm32-dma: Add DMA/MDMA chaining support
>   dmaengine: stm32-mdma: Add DMA/MDMA chaining support
>   dmaengine: stm32-dma: enable descriptor_reuse
>   dmaengine: stm32-mdma: enable descriptor_reuse
> 
>  .../devicetree/bindings/dma/stm32-dma.txt          |  27 +-
>  .../devicetree/bindings/dma/stm32-dmamux.txt       |   6 +-
>  .../devicetree/bindings/dma/stm32-mdma.txt         |  12 +-
>  drivers/dma/stm32-dma.c                            | 903 ++++++++++++++++++---
>  drivers/dma/stm32-mdma.c                           | 133 ++-
>  5 files changed, 949 insertions(+), 132 deletions(-)
>