linux-kernel - Re: [PATCH 1/5] dt-bindings: dma: dw: Add optional DMA-channels mask cell support

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Date:   Fri, 31 Jul 2020 16:42:13 -0600
From:   Rob Herring <robh@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        linux-kernel@...r.kernel.org, Viresh Kumar <vireshk@...nel.org>,
        devicetree@...r.kernel.org, Vinod Koul <vkoul@...nel.org>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        dmaengine@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Serge Semin <fancer.lancer@...il.com>
Subject: Re: [PATCH 1/5] dt-bindings: dma: dw: Add optional DMA-channels mask
 cell support

On Thu, 30 Jul 2020 18:45:41 +0300, Serge Semin wrote:
> Each DW DMA controller channel can be synthesized with different
> parameters like maximum burst-length, multi-block support, maximum data
> width, etc. Most of these parameters determine the DW DMAC channels
> performance in its own aspect. On the other hand these parameters can
> be implicitly responsible for the channels performance degradation
> (for instance multi-block support is a very useful feature, but having
> it disabled during the DW DMAC synthesize will provide a more optimized
> core). Since DMA slave devices may have critical dependency on the DMA
> engine performance, let's provide a way for the slave devices to have
> the DMA-channels allocated from a pool of the channels, which according
> to the system engineer fulfill their performance requirements.
> 
> The pool is determined by a mask optionally specified in the fifth
> DMA-cell of the DMA DT-property. If the fifth cell is omitted from the
> phandle arguments or the mask is zero, then the allocation will be
> performed from a set of all channels provided by the DMA controller.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> ---
>  .../devicetree/bindings/dma/snps,dma-spear1340.yaml        | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 

Reviewed-by: Rob Herring <robh@...nel.org>