linux-kernel - Re: [PATCH 2/2] dt-bindings: Add DT bindings info for FlexRM mailbox driver

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Date:   Wed, 30 Nov 2016 15:38:54 -0600
From:   Rob Herring <robh@...nel.org>
To:     Anup Patel <anup.patel@...adcom.com>
Cc:     Jassi Brar <jassisinghbrar@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Pramod KUMAR <pramod.kumar@...adcom.com>,
        Rob Rice <rob.rice@...adcom.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH 2/2] dt-bindings: Add DT bindings info for FlexRM mailbox
 driver

On Fri, Nov 25, 2016 at 10:05:51AM +0530, Anup Patel wrote:
> This patch adds device tree bindings document for the FlexRM
> mailbox driver.

Bindings document h/w, not drivers.

> 
> Reviewed-by: Ray Jui <ray.jui@...adcom.com>
> Reviewed-by: Scott Branden <scott.branden@...adcom.com>
> Signed-off-by: Anup Patel <anup.patel@...adcom.com>
> ---
>  .../bindings/mailbox/brcm,flexrm-mbox.txt          | 60 ++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/brcm,flexrm-mbox.txt
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/brcm,flexrm-mbox.txt b/Documentation/devicetree/bindings/mailbox/brcm,flexrm-mbox.txt
> new file mode 100644
> index 0000000..7969b1c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/brcm,flexrm-mbox.txt
> @@ -0,0 +1,60 @@
> +Broadcom FlexRM Mailbox Driver

h/w

> +===============================
> +The Broadcom FlexRM ring manager provides a set of rings which can be
> +used to submit work to offload engines. An SoC may have multiple FlexRM
> +hardware blocks. There is one device tree entry per block. The FlexRM
> +mailbox drivers creates a mailbox instance using FlexRM rings where
> +each mailbox channel is a separate FlexRM ring.
> +
> +Required properties:
> +--------------------
> +- compatible:	Should be "brcm,flexrm-mbox"

Sounds generic. Add SoC specific compatible strings please.

> +- reg:		Specifies base physical address and size of the FlexRM
> +		ring registers
> +- msi-parent:	Phandles (and potential Device IDs) to MSI controllers
> +		The FlexRM engine will send MSIs (instead of wired
> +		interrupts) to CPU. There is one MSI for each FlexRM ring.

One ring is one h/w block, right? How many instances is not really 
relevant.

> +		Refer devicetree/bindings/interrupt-controller/msi.txt
> +- #mbox-cells:	Specifies the number of cells needed to encode a mailbox
> +		channel. This should be 3.
> +
> +		The 1st cell is the mailbox channel number.
> +
> +		The 2nd cell contains MSI completion threshold. This is the
> +		number of completion messages for which FlexRM will inject
> +		one MSI interrupt to CPU.
> +
> +		The 3nd cell contains MSI timer value representing time for
> +		which FlexRM will wait to accumulate N completion messages
> +		where N is the value specified by 2nd cell above. If FlexRM
> +		does not get required number of completion messages in time
> +		specified by this cell then it will inject one MSI interrupt
> +		to CPU provided atleast one completion message is available.
> +
> +Optional properties:
> +--------------------
> +- dma-coherent:	Present if DMA operations made by the FlexRM engine (such
> +		as DMA descriptor access, access to buffers pointed by DMA
> +		descriptors and read/write pointer updates to DDR) are
> +		cache coherent with the CPU.
> +
> +Example:
> +--------
> +crypto_mbox: mbox@...00000 {
> +	compatible = "brcm,flexrm-mbox";
> +	reg = <0x67000000 0x200000>;
> +	msi-parent = <&gic_its 0x7f00>;
> +	#mbox-cells = <3>;
> +};
> +
> +crypto_client {

Is this a h/w block or purely a driver on top of the mailbox? The latter 
doesn't belong in DT.

> +	...
> +	mboxes = <&crypto_mbox 0 0x1 0xffff>,
> +		 <&crypto_mbox 1 0x1 0xffff>,
> +		 <&crypto_mbox 16 0x1 0xffff>,
> +		 <&crypto_mbox 17 0x1 0xffff>,
> +		 <&crypto_mbox 30 0x1 0xffff>,
> +		 <&crypto_mbox 31 0x1 0xffff>;
> +	};
> +	...
> +};
> -- 
> 2.7.4
>