linux-kernel - Re: [PATCH 1/2] Documentation: dt: mailbox: Add TI Message Manager

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Date:	Mon, 8 Feb 2016 13:37:06 -0600
From:	Rob Herring <robh@...nel.org>
To:	Nishanth Menon <nm@...com>
Cc:	Jassi Brar <jassisinghbrar@...il.com>, Suman Anna <s-anna@...com>,
	Franklin S Cooper Jr <fcooper@...com>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Santosh Shilimkar <ssantosh@...nel.org>
Subject: Re: [PATCH 1/2] Documentation: dt: mailbox: Add TI Message Manager

On Fri, Feb 05, 2016 at 10:34:03AM -0600, Nishanth Menon wrote:
> Message Manager is a hardware block used to communicate with various
> processor systems within certain Texas Instrument's Keystone
> generation SoCs.
> 
> This hardware engine is used to transfer messages from various compute
> entities(or processors) within the SoC. It is designed to be self
> contained without needing software initialization for operation.
> 
> Signed-off-by: Nishanth Menon <nm@...com>
> ---
>  .../bindings/mailbox/ti,message-manager.txt        | 72 ++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/ti,message-manager.txt
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/ti,message-manager.txt b/Documentation/devicetree/bindings/mailbox/ti,message-manager.txt
> new file mode 100644
> index 000000000000..f3d73b0b3c66
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/ti,message-manager.txt
> @@ -0,0 +1,72 @@
> +Texas Instruments' Message Manager Driver
> +========================================
> +
> +The Texas Instruments' Message Manager is a mailbox controller that has
> +configurable queues selectable at SoC(System on Chip) integration. The Message
> +manager is broken up into queues in different address regions that are called
> +"proxies" - each instance is unidirectional and is instantiated at SoC
> +integration level to indicate receive or transmit path.
> +
> +Message Manager Device Node:
> +===========================
> +
> +Required properties:
> +--------------------
> +- compatible:		Shall be:
> +				"ti,k2g-message-manager"
> +				"ti,message-manager"

Given that queues are configurable at integration time, does a generic 
property really make sense here?

> +- reg-names 		queue_proxy_region - Map the queue Proxy region
> +			queue_state_debug_region - Map the queue state debug
> +			region.
> +- reg:			Contains the register map per reg-names
> +- #mbox-cells		Shall be 1

And the value contained is what?

> +
> +Child Nodes:
> +============
> +A child node is used for representing the actual queue device that is
> +used for the communication between the host processor and a remote processor.
> +Each child node should have a unique node name across all the different
> +message manager device nodes.
> +
> +Required Properties:
> +--------------------
> +- ti,queue-id:		Indicates the queue number this node represents
> +- ti,proxy-id:		Proxy ID representing the processor in the SoC.

What determines these values?

> +
> +Optional Properties:
> +--------------------
> +- interrupt-names:	'rx' - indicates a receive interrupt (mandatory ONLY if
> +			this is a receive queue)

Kind of pointless if there is only 1.

> +- interrupts:		Contains the interrupt information corresponding to
> +			interrupt-names property.
> +
> +Example:
> +--------
> +
> +	msgmgr: msgmgr@...00000 {
> +		compatible = "ti,k2g-message-manager", "ti,message-manager";
> +		#mbox-cells = <1>;
> +		reg-names = "queue_proxy_region", "queue_state_debug_region";
> +		reg = <0x02a00000 0x400000>, <0x028c3400 0x400>;
> +
> +		msgmgr_proxy_pmmc_tx_prio0: pmmc_tx_prio0 {
> +			ti,queue-id = <0>;
> +			ti,proxy-id = <0>;
> +		};
> +
> +		msgmgr_proxy_pmmc_rx: pmmc_rx {
> +			ti,queue-id = <5>;
> +			ti,proxy-id = <2>;
> +			interrupt-names = "rx";
> +			interrupts = <GIC_SPI 324 IRQ_TYPE_EDGE_RISING>;
> +		};
> +	};
> +
> +...
> +	pmmc {
> +		...
> +		mbox-names = "tx", "rx";
> +		mboxes = <&msgmgr &msgmgr_proxy_pmmc_tx>
> +			 <&msgmgr &msgmgr_proxy_pmmc_rx>;

While I guess this is valid DT, it is a bit strange having the cell 
values be phandles. Why not just make the queue and proxy ids be the 
cell values? The interrupts could be moved to the parent and the child 
nodes eliminated altogether.

The alternative would be just drop msgmgr phandle and point to the child 
nodes. I prefer getting rid of the child nodes though.

Rob