Re: [PATCH 2/4] dt-bindings: arm: fsl: add mu binding doc

[Rob Herring <robh@kernel.org>]

On Sat, Apr 28, 2018 at 02:46:14AM +0800, Dong Aisheng wrote:
> The Messaging Unit module enables two processors within
> the SoC to communicate and coordinate by passing messages
> (e.g. data, status and control) through the MU interface.
> 
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Sascha Hauer <kernel@pengutronix.de>
> Cc: Fabio Estevam <fabio.estevam@nxp.com>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> ---
>  .../devicetree/bindings/arm/freescale/fsl,mu.txt   | 33 ++++++++++++++++++++++

bindings/mailbox/ ?

Why aren't you using the mailbox binding?

>  1 file changed, 33 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/freescale/fsl,mu.txt
> 
> diff --git a/Documentation/devicetree/bindings/arm/freescale/fsl,mu.txt b/Documentation/devicetree/bindings/arm/freescale/fsl,mu.txt
> new file mode 100644
> index 0000000..a7ceb1f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/freescale/fsl,mu.txt
> @@ -0,0 +1,33 @@
> +NXP i.MX Messaging Unit (MU)
> +--------------------------------------------------------------------
> +
> +The Messaging Unit module enables two processors within the SoC to
> +communicate and coordinate by passing messages (e.g. data, status
> +and control) through the MU interface. The MU also provides the ability
> +for one processor to signal the other processor using interrupts.
> +
> +Because the MU manages the messaging between processors, the MU uses
> +different clocks (from each side of the different peripheral buses).
> +Therefore, the MU must synchronize the accesses from one side to the
> +other. The MU accomplishes synchronization using two sets of matching
> +registers (Processor A-facing, Processor Bfacing).

B-facing

> +
> +Messaging Unit Device Node:
> +=============================
> +
> +Required properties:
> +-------------------
> +- compatible :	should be "fsl,<chip>-mu", the supported chips include
> +		imx6sx, imx7d, imx7ulp, imx8qxp, imx8qm, imx8mq.

'qm' and 'mq' are really both parts?

> +- reg :		Should contain the registers location and length
> +- interrupts :	Interrupt number. The interrupt specifier format depends
> +		on the interrupt controller parent.
> +
> +Examples:
> +--------
> +lsio_mu0: mu@5d1b0000 {
> +	compatible = "fsl,imx8qxp-mu", "fsl,imx6sx-mu";

It is not clear from the definition above that fsl,imx6sx-mu is a 
fallback. Is that true for all the other chips too?

> +	reg = <0x0 0x5d1b0000 0x0 0x10000>;

Really has 64KB of registers? You are just wasting virtual address space 
which is scarce on 32-bit processors with GBs of RAM.

> +	interrupts = <GIC_SPI 176 IRQ_TYPE_LEVEL_HIGH>;
> +	status = "okay";

Don't show status in examples.

> +};
> -- 
> 2.7.4
> 
> --
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