linux-kernel - Re: [PATCH 4/4] Update device tree Synopsys DW DMAC documentation

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Date:   Wed, 16 Nov 2016 17:10:42 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        devicetree@...r.kernel.org
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        linux-kernel@...r.kernel.org, vireshk@...nel.org,
        dan.j.williams@...el.com, vinod.koul@...el.com,
        dmaengine@...r.kernel.org, linux-snps-arc@...ts.infradead.org
Subject: Re: [PATCH 4/4] Update device tree Synopsys DW DMAC documentation

On Wed, 2016-11-16 at 16:56 +0300, Eugeniy Paltsev wrote:
>  * Rename is_private to is-private as ordered by DT policy.
>  The change leaves the support for the old format.
> 
>  * Add is-memcpu property, so it is possible to
>  enable memory-to-memory transfers support via DT.
> 
>  * Add hw-llp property, so it is possible to enable
>  hardware multi block transfers support via DT.
> 
>  Fix white spaces.
> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> ---
>  Documentation/devicetree/bindings/dma/snps-dma.txt | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt
> b/Documentation/devicetree/bindings/dma/snps-dma.txt
> index 0f55832..d41d960 100644
> --- a/Documentation/devicetree/bindings/dma/snps-dma.txt
> +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
> @@ -20,13 +20,19 @@ Required properties:
>  Deprecated properties:
>  - data_width: Maximum data width supported by hardware per AHB master
>    (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)

> +- is_private: The device channels should be marked as private and not
> for by the
> +  general purpose DMA channel allocator. False if not passed.

This...

>  
>  
>  Optional properties:
>  - interrupt-parent: Should be the phandle for the interrupt
> controller
>    that services interrupts for this device

> -- is_private: The device channels should be marked as private and not
> for by the
> +- is-private: The device channels should be marked as private and not
> for by the
>    general purpose DMA channel allocator. False if not passed.

...and this is a part of patch 1.

> +- is-memcpu: The device channels do support memory-to-memory 

memcpy

> transfers. 

> False
> +  if not passed.
> +- hw-llp: Multi block transfers supported by hardware per AHB master.
> +  0 (default): not supported, 1: supported.

Overall, since we are going to expose some properties to the Device Tree
I would really think twice about naming. Better if we reuse something
existing already.

So, what I can see is

dmacap,private
dmacap,memcpy

Here is a selling point as well, i.e. standardization.

'hw-llp' sounds too tricky, perhaps 'multi-block' is better and could be
re-used.

>  
>  Example:
>  
> @@ -56,7 +62,7 @@ The four cells in order are:
>  4. Peripheral master for transfers on allocated channel
>  

>  Example:
> -	
> +

No, no need to touch this.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy