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Subject: Re: [PATCH v8 4/9] mfd: Add binding document for NVIDIA Tegra XUSB
From: Andrew Bresticker <abrestic@chromium.org>
To: Lee Jones <lee.jones@linaro.org>
Cc: Stephen Warren <swarren@wwwdotorg.org>,
        Thierry Reding <thierry.reding@gmail.com>,
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Lee,

On Wed, May 13, 2015 at 7:39 AM, Lee Jones <lee.jones@linaro.org> wrote:
> On Mon, 04 May 2015, Andrew Bresticker wrote:
>
>> Add a binding document for the XUSB host complex on NVIDIA Tegra124
>> and later SoCs.  The XUSB host complex includes a mailbox for
>> communication with the XUSB micro-controller and an xHCI host-controller.
>>
>> Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: Pawel Moll <pawel.moll@arm.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
>> Cc: Kumar Gala <galak@codeaurora.org>
>> Cc: Samuel Ortiz <sameo@linux.intel.com>
>> Cc: Lee Jones <lee.jones@linaro.org>
>> ---
>> Changes from v7:
>>  - Move non-shared resources into child nodes.
>> New for v7.
>> ---
>>  .../bindings/mfd/nvidia,tegra124-xusb.txt          | 37 ++++++++++++++++++++++
>>  1 file changed, 37 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/mfd/nvidia,tegra124-xusb.txt
>>
>> diff --git a/Documentation/devicetree/bindings/mfd/nvidia,tegra124-xusb.txt b/Documentation/devicetree/bindings/mfd/nvidia,tegra124-xusb.txt
>> new file mode 100644
>> index 0000000..bc50110
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mfd/nvidia,tegra124-xusb.txt
>> @@ -0,0 +1,37 @@
>> +NVIDIA Tegra XUSB host copmlex
>> +==============================
>> +
>> +The XUSB host complex on Tegra124 and later SoCs contains an xHCI host
>> +controller and a mailbox for communication with the XUSB micro-controller.
>> +
>> +Required properties:
>> +--------------------
>> + - compatible: For Tegra124, must contain "nvidia,tegra124-xusb".
>> +   Otherwise, must contain '"nvidia,<chip>-xusb", "nvidia,tegra124-xusb"'
>> +   where <chip> is tegra132.
>> + - reg: Must contain the base and length of the XUSB FPCI registers.
>> + - ranges: Bus address mapping for the XUSB block.  Can be empty since the
>> +   mapping is 1:1.
>> + - #address-cells: Must be 2.
>> + - #size-cells: Must be 2.
>> +
>> +Example:
>> +--------
>> +     usb@0,70098000 {
>> +             compatible = "nvidia,tegra124-xusb";
>> +             reg = <0x0 0x70098000 0x0 0x1000>;
>> +             ranges;
>> +
>> +             #address-cells = <2>;
>> +             #size-cells = <2>;
>> +
>> +             usb-host@0,70090000 {
>> +                     compatible = "nvidia,tegra124-xhci";
>> +                     ...
>> +             };
>> +
>> +             mailbox {
>> +                     compatible = "nvidia,tegra124-xusb-mbox";
>> +                     ...
>> +             };
>
> This doesn't appear to be a proper MFD.  I would have the USB and
> Mailbox devices probe seperately and use a phandle to point the USB
> device to its Mailbox.
>
> usb@xyz {
>         mboxes = <&xusb-mailbox, [chan]>;
> };

Then what will set up the shared regmap?  The point of using an MFD
here was to share a register set with both the mailbox and xHCI
drivers and avoid having to map the same register set twice in two
separate drivers.

Thanks,
Andrew
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