Re: [PATCH 2/3] dmaengine: sun6i: Add support for Allwinner A23 (sun8i) variant

[Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

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On Sat, Sep 13, 2014 at 09:53:00PM +0800, Chen-Yu Tsai wrote:
> The A23 SoC has the same dma engine as the A31 (sun6i), with a
> reduced amount of endpoints and physical channels. Add the proper
> config data and compatible string to support it.
> 
> A slight difference in sun8i is an undocumented register needs
> to be toggled for dma to function.
> 
> Signed-off-by: Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/dma/sun6i-dma.txt |  2 +-
>  drivers/dma/Kconfig                                 |  4 ++--
>  drivers/dma/sun6i-dma.c                             | 20 ++++++++++++++++++++
>  3 files changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/sun6i-dma.txt b/Documentation/devicetree/bindings/dma/sun6i-dma.txt
> index 3e145c1..9cdcba24d 100644
> --- a/Documentation/devicetree/bindings/dma/sun6i-dma.txt
> +++ b/Documentation/devicetree/bindings/dma/sun6i-dma.txt
> @@ -4,7 +4,7 @@ This driver follows the generic DMA bindings defined in dma.txt.
>  
>  Required properties:
>  
> -- compatible:	Must be "allwinner,sun6i-a31-dma"
> +- compatible:	Must be "allwinner,sun6i-a31-dma" or "allwinner,sun8i-a23-dma"
>  - reg:		Should contain the registers base address and length
>  - interrupts:	Should contain a reference to the interrupt used by this device
>  - clocks:	Should contain a reference to the parent AHB clock
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index 9b1ea0e..5361aa7 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -395,12 +395,12 @@ config XILINX_VDMA
>  
>  config DMA_SUN6I
>  	tristate "Allwinner A31 SoCs DMA support"
> -	depends on MACH_SUN6I || COMPILE_TEST
> +	depends on MACH_SUN6I || MACH_SUN8I || COMPILE_TEST
>  	depends on RESET_CONTROLLER
>  	select DMA_ENGINE
>  	select DMA_VIRTUAL_CHANNELS
>  	help
> -	  Support for the DMA engine for Allwinner A31 SoCs.
> +	  Support for the DMA engine first found in Allwinner A31 SoCs.
>  
>  config NBPFAXI_DMA
>  	tristate "Renesas Type-AXI NBPF DMA support"
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index 89ca0c4..29667dd 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -878,8 +878,20 @@ static struct sun6i_dma_config sun6i_a31_dma_cfg = {
>  	.nr_max_vchans   = 53,
>  };
>  
> +/*
> + * The A23 only has 8 physical channels, a maximum DRQ port id of 24,
> + * and a total of 37 usable source and destination endpoints.
> + */
> +
> +static struct sun6i_dma_config sun8i_a23_dma_cfg = {
> +	.nr_max_channels = 8,
> +	.nr_max_requests = 24,
> +	.nr_max_vchans   = 37,
> +};
> +
>  static struct of_device_id sun6i_dma_match[] = {
>  	{ .compatible = "allwinner,sun6i-a31-dma", .data = &sun6i_a31_dma_cfg },
> +	{ .compatible = "allwinner,sun8i-a23-dma", .data = &sun8i_a23_dma_cfg },
>  	{ /* sentinel */ }
>  };
>  
> @@ -1008,6 +1020,14 @@ static int sun6i_dma_probe(struct platform_device *pdev)
>  		goto err_dma_unregister;
>  	}
>  
> +	/*
> +	 * sun8i variant requires us to toggle an undocumented register,
> +	 * as seen in Allwinner's SDK.

The BSP I have has this:

static void sunxi_dma_hw_init(struct sunxi_dmadev *dev)
{
        struct sunxi_dmadev *sunxi_dev = dev;

        clk_prepare_enable(sunxi_dev->ahb_clk);
#ifdef CONFIG_ARCH_SUN8IW3
        writel(0x04, sunxi_dev->base + DMA_GATE);
#endif
}

/* All is ok, and open the clock */
sunxi_dma_hw_init(sunxi_dev);

So I guess we can say that it's not that undocumented :)

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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