Date:	Mon, 8 Feb 2016 14:31:40 -0600
From:	Nishanth Menon <nm@...com>
To:	Rob Herring <robh@...nel.org>
Cc:	dt list <devicetree@...r.kernel.org>,
	Jassi Brar <jassisinghbrar@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Franklin S Cooper Jr <fcooper@...com>
Subject: Re: [PATCH 1/2] Documentation: dt: mailbox: Add TI Message Manager

On Mon, Feb 8, 2016 at 1:37 PM, Rob Herring <robh@...nel.org> wrote:

Thank you for reviewing the binding.

> 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?

True. I can drop the generic "ti,message-manager" binding.

>> +- 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?

phandle -> I think Suman has already explained in his response.

>> +
>> +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?

This is SoC integration dependent -> Every queue, proxy combination
has it's own memory region allocated for it.

>> +
>> +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.
>

This is primarily to ensure a future compatibility where we are trying
to convince the hardware team to provide an error interrupt per queue
as well for slave usage.
it would probably be pointless at that time to deal with "legacy"
binding defintions when the next hardware ip definition takes place.

>> +- 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.

I see that Suman has already responded to this.

--
Regards,
Nishanth Menon

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