linux-kernel - Re: [PATCH 1/2] dt-bindings: Document the STM32 MDMA bindings

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Message-ID: <20170320215250.wwhq6lzwe45jmwks@rob-hp-laptop>
Date:   Mon, 20 Mar 2017 16:52:50 -0500
From:   Rob Herring <robh@...nel.org>
To:     M'boumba Cedric Madianga <cedric.madianga@...il.com>
Cc:     vinod.koul@...el.com, mark.rutland@....com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        dan.j.williams@...el.com, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: Document the STM32 MDMA bindings

On Mon, Mar 13, 2017 at 04:06:38PM +0100, M'boumba Cedric Madianga wrote:
> This patch adds documentation of device tree bindings for the STM32 MDMA
> controller.
> 
> Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@...il.com>
> Reviewed-by: Ludovic BARRE <ludovic.barre@...com>
> ---
>  .../devicetree/bindings/dma/stm32-mdma.txt         | 94 ++++++++++++++++++++++
>  1 file changed, 94 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/stm32-mdma.txt
> 
> diff --git a/Documentation/devicetree/bindings/dma/stm32-mdma.txt b/Documentation/devicetree/bindings/dma/stm32-mdma.txt
> new file mode 100644
> index 0000000..26a930c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/stm32-mdma.txt
> @@ -0,0 +1,94 @@
> +* STMicroelectronics STM32 MDMA controller
> +
> +The STM32 MDMA is a general-purpose direct memory access controller capable of
> +supporting 64 independent DMA channels with 256 HW requests.
> +
> +Required properties:
> +- compatible: Should be "st,stm32-mdma"

Should be more specific.

> +- reg: Should contain MDMA registers location and length. This should include
> +  all of the per-channel registers.
> +- interrupts: Should contain the MDMA interrupt.
> +- clocks: Should contain the input clock of the DMA instance.
> +- resets: Reference to a reset controller asserting the DMA controller.
> +- #dma-cells : Must be <5>. See DMA client paragraph for more details.
> +
> +Optional properties:
> +- dma-channels: Number of DMA channels supported by the controller.
> +- dma-requests: Number of DMA request signals supported by the controller.
> +- st,ahb-addr-masks: Array of u32 mask to list memory devices addressed via
> +  AHB bus.

I don't understand what this is.

> +
> +Example:

Put the 2 examples together.

> +
> +	mdma1: dma@...00000 {
> +		compatible = "st,stm32-mdma";
> +		reg = <0x52000000 0x1000>;
> +		interrupts = <122>;
> +		clocks = <&clk_dummy>;
> +		resets = <&rcc 992>;
> +		#dma-cells = <5>;
> +		dma-channels = <16>;
> +		dma-requests = <32>;
> +		st,ahb-addr-masks = <0x20000000>, <0x00000000>;
> +	};
> +
> +* DMA client
> +
> +DMA clients connected to the STM32 MDMA controller must use the format
> +described in the dma.txt file, using a six-cell specifier for each channel:
> +a phandle to the MDMA controller plus the following five integer cells:
> +
> +1. The request line number
> +2. The priority level
> +	0x00: Low
> +	0x01: Medium
> +	0x10: High
> +	0x11: Very high
> +3. A 32bit mask specifying the DMA channel configuration
> + -bit 0-1: Source increment mode
> +	0x00: Source address pointer is fixed
> +	0x10: Source address pointer is incremented after each data transfer
> +	0x11: Source address pointer is decremented after each data transfer
> + -bit 2-3: Destination increment mode
> +	0x00: Destination address pointer is fixed
> +	0x10: Destination address pointer is incremented after each data
> +	transfer
> +	0x11: Destination address pointer is decremented after each data
> +	transfer
> + -bit 8-9: Source increment offset size
> +	0x00: byte (8bit)
> +	0x01: half-word (16bit)
> +	0x10: word (32bit)
> +	0x11: double-word (64bit)
> + -bit 10-11: Destination increment offset size
> +	0x00: byte (8bit)
> +	0x01: half-word (16bit)
> +	0x10: word (32bit)
> +	0x11: double-word (64bit)
> +-bit 25-18: The number of bytes to be transferred in a single transfer
> +	(min = 1 byte, max = 128 bytes)
> +-bit 29:28: Trigger Mode
> +	0x00: Each MDMA request triggers a buffer transfer (max 128 bytes)
> +	0x01: Each MDMA request triggers a block transfer (max 64K bytes)
> +	0x10: Each MDMA request triggers a repeated block transfer
> +	0x11: Each MDMA request triggers a linked list transfer
> +4. A 32bit value specifying the register to be used to acknowledge the request
> +   if no HW ack signal is used by the MDMA client
> +5. A 32bit mask specifying the value to be written to acknowledge the request
> +   if no HW ack signal is used by the MDMA client
> +
> +Example:
> +
> +	i2c4: i2c@...02000 {
> +		compatible = "st,stm32f7-i2c";
> +		reg = <0x5c002000 0x400>;
> +		interrupts = <GIC_SPI 95 IRQ_TYPE_NONE>,
> +			     <GIC_SPI 96 IRQ_TYPE_NONE>;
> +		clocks = <&clk_hsi>;
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		dmas = <&mdma1 36 0x0 0x40008 0x0 0x0>,
> +		       <&mdma1 37 0x0 0x40002 0x0 0x0>;
> +		dma-names = "rx", "tx";
> +		status = "disabled";
> +	};
> -- 
> 1.9.1
>