linux-kernel - Re: [PATCH 02/14] dmaengine: dma-jz4780: Separate chan/ctrl registers

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Date:   Mon, 9 Jul 2018 22:33:59 +0530
From:   Vinod <vkoul@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>,
        Mathieu Malaterre <malat@...ian.org>,
        Daniel Silsby <dansilsby@...il.com>, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...ux-mips.org
Subject: Re: [PATCH 02/14] dmaengine: dma-jz4780: Separate chan/ctrl registers

On 03-07-18, 14:32, Paul Cercueil wrote:
> The register area of the JZ4780 DMA core can be split into different
> sections for different purposes:
> 
> * one set of registers is used to perform actions at the DMA core level,
> that will generally affect all channels;
> 
> * one set of registers per DMA channel, to perform actions at the DMA
> channel level, that will only affect the channel in question.
> 
> The problem rises when trying to support new versions of the JZ47xx
> Ingenic SoC. For instance, the JZ4770 has two DMA cores, each one
> with six DMA channels, and the register sets are interleaved:
> <DMA0 chan regs> <DMA1 chan regs> <DMA0 ctrl regs> <DMA1 ctrl regs>
> 
> By using one memory resource for the channel-specific registers and
> one memory resource for the core-specific registers, we can support
> the JZ4770, by initializing the driver once per DMA core with different
> addresses.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  .../devicetree/bindings/dma/jz4780-dma.txt    |   6 +-

Pls move to separate patch.

>  drivers/dma/dma-jz4780.c                      | 106 +++++++++++-------
>  2 files changed, 69 insertions(+), 43 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/jz4780-dma.txt b/Documentation/devicetree/bindings/dma/jz4780-dma.txt
> index f25feee62b15..f9b1864f5b77 100644
> --- a/Documentation/devicetree/bindings/dma/jz4780-dma.txt
> +++ b/Documentation/devicetree/bindings/dma/jz4780-dma.txt
> @@ -3,7 +3,8 @@
>  Required properties:
>  
>  - compatible: Should be "ingenic,jz4780-dma"
> -- reg: Should contain the DMA controller registers location and length.
> +- reg: Should contain the DMA channel registers location and length, followed
> +  by the DMA controller registers location and length.
>  - interrupts: Should contain the interrupt specifier of the DMA controller.
>  - interrupt-parent: Should be the phandle of the interrupt controller that
>  - clocks: Should contain a clock specifier for the JZ4780 PDMA clock.
> @@ -22,7 +23,8 @@ Example:
>  
>  dma: dma@...20000 {
>  	compatible = "ingenic,jz4780-dma";
> -	reg = <0x13420000 0x10000>;
> +	reg = <0x13420000 0x400
> +	       0x13421000 0x40>;

Second should be optional or we break platform which may not have
updated DT..

> -	jzdma->base = devm_ioremap_resource(dev, res);
> -	if (IS_ERR(jzdma->base))
> -		return PTR_ERR(jzdma->base);
> +	jzdma->chn_base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(jzdma->chn_base))
> +		return PTR_ERR(jzdma->chn_base);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +	if (!res) {
> +		dev_err(dev, "failed to get I/O memory\n");
> +		return -EINVAL;
> +	}

okay and this breaks if you happen to get probed on older DT. I think DT
is treated as ABI so you need to continue support older method while
finding if DT has split resources

-- 
~Vinod