Re: [PATCH v2 1/9] of: Add NVIDIA Tegra XUSB mailbox binding

From: Stephen Warren
Date: Mon Aug 25 2014 - 14:48:33 EST

On 08/18/2014 11:08 AM, Andrew Bresticker wrote:
Add device-tree bindings for the Tegra XUSB mailbox which will be used
for communication between the Tegra xHCI controller's firmware and the
host processor.

diff --git a/Documentation/devicetree/bindings/mailbox/nvidia,tegra124-xusb-mbox.txt b/Documentation/devicetree/bindings/mailbox/nvidia,tegra124-xusb-mbox.txt

+NVIDIA Tegra XUSB mailbox
+The Tegra XUSB mailbox is used by the Tegra xHCI controller's firmware to
+communicate requests to the host and PHY drivers.
+Required properties:
+ - compatible: Should be "nvidia,tegra124-xusb-mbox".
+ - reg: Address and length of the XUSB FPCI registers.
+ - interrupts: XUSB mailbox interrupt.
+ - #mbox-cells: Should be 1. The specifier is the index of the mailbox to
+ reference. See <dt-bindings/mailbox/tegra-xusb-mailbox.h> for the list
+ of valid values.

Is there a common mailbox binding somewhere? I couldn't find one. While the text above specifies the value for #mbox-cells, it doesn't specify the details of what the property is used for (i.e. there's no documentation of the consumer-side of this property, for parsing the mboxes property). Typically, that would be part of a subsystem's common binding document, and that document would be referenced here.

diff --git a/include/dt-bindings/mailbox/tegra-xusb-mailbox.h b/include/dt-bindings/mailbox/tegra-xusb-mailbox.h


I can't work out how these values relate to hardware at all. Are they in fact properties of the particular firmware that's loaded into the XUSB module? If so, I don't think the DT should contain these values at all. I wonder if the individual MBOX_CMD_* values from patch 2 are any better, although I think those are also defined by the firmware, not the hardware?
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