Re: [PATCH v8 4/9] mfd: Add binding document for NVIDIA Tegra XUSB

[Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On Thu, 14 May 2015, Jon Hunter wrote:
> On 14/05/15 10:30, Lee Jones wrote:
> > On Thu, 14 May 2015, Jon Hunter wrote:
> >> On 14/05/15 08:40, Lee Jones wrote:
> >>> On Thu, 14 May 2015, Jon Hunter wrote:
> >>>> On 13/05/15 15:39, Lee Jones 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-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> >>>>>> Cc: Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> >>>>>> Cc: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
> >>>>>> Cc: Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>
> >>>>>> Cc: Ian Campbell <ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org>
> >>>>>> Cc: Kumar Gala <galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
> >>>>>> Cc: Samuel Ortiz <sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> >>>>>> Cc: Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.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]>;
> >>>>> };
> >>>>>
> >>>>
> >>>> I am assuming that Andrew had laid it out like this to reflect the hw
> >>>> structure. The mailbox and xhci controller are part of the xusb
> >>>> sub-system and hence appear as child nodes. My understanding is that for
> >>>> device-tree we want the device-tree structure to reflect the actual hw.
> >>>> Is this not the case?
> >>>
> >>> Yes, the DT files should reflect h/w.  I have requested to see what
> >>> the memory map looks like, so I might provide a more appropriate
> >>> solution to accepting a pretty pointless MFD.
> >>
> >> For the xusb-host has memory from 0x7009000 - 0x7009ffff.
> >>
> >> Within this range, we have this fpci range which is defined as 0x7009800
> >> - 0x70098fff. This range is being shared between the mailbox and xhci
> >> drivers. Looking at the drivers, we have ...
> >>
> >> mailbox uses: 0x700980e0 - 0x700980f3 and 0x70098428 - 0x7009842b.
> >> xhci uses:    0x70098000 - 0x700980cf and 0x70098800 - 0x70098803.
> >>
> >> So it is a bit messy as they overlap. However, we could have ...
> >>
> >> 	xusb_mbox: mailbox {
> >> 		compatible = "nvidia,tegra124-xusb-mbox";
> >> 		reg = <0x0 0x700980e0 0x0 0x14>,
> >> 		      <0x0 0x70098428 0x0 0x4>;
> >> 		...
> >> 	};
> >> 	usb-host@0,70090000 {
> >> 		compatible = "nvidia,tegra124-xhci";
> >> 		reg = <0x0 0x70090000 0x0 0x8000>,		      	
> >> 		      <0x0 0x70098000 0x0 0x00d0>;
> >> 		      <0x0 0x70098800 0x0 0x0004>;
> >> 		      <0x0 0x70099000 0x0 0x1000>;
> >> 		...
> >> 	};
> >>
> >> I believe that Thierry and Stephen said that they wished to avoid
> >> multiple devices sharing the same memory ranges, and so we would need to
> >> divvy up the memory map as above. However, I am not sure if this is an
> >> ok thing to do.
> >> 	
> >>> Two solutions spring to mind.  You can either call
> >>> of_platform_populate() from the USB driver, as some already do:
> >>>
> >>>   drivers/usb/dwc3/dwc3-exynos.c:
> >>>     ret = of_platform_populate(node, NULL, NULL, dev);
> >>>   drivers/usb/dwc3/dwc3-keystone.c:
> >>>     error = of_platform_populate(node, NULL, NULL, dev);
> >>>   drivers/usb/dwc3/dwc3-omap.c:
> >>>     ret = of_platform_populate(node, NULL, NULL, dev);
> >>>   drivers/usb/dwc3/dwc3-qcom.c:
> >>>     ret = of_platform_populate(node, NULL, NULL, qdwc->dev);
> >>>   drivers/usb/dwc3/dwc3-st.c:
> >>>     ret = of_platform_populate(node, NULL, NULL, dev);
> >>>   drivers/usb/musb/musb_am335x.c:
> >>>     ret = of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
> >>>
> >>> Or use the "simple-mfd", which is currently in -next:
> >>>
> >>>   git show next/master:Documentation/devicetree/bindings/mfd/mfd.txt
> >>
> >> That is nice. Sounds like the "simple-bus" style of device but for an
> > 
> > That's precisely what it does.  FYI: You 'can' use "simple-bus" and it
> > will do the right thing, but as an MFD isn't really a bus, it was
> > decided to create something a little more fitting.
> > 
> >> mfd. Based upon the above, let me know if you think we could use the
> >> "simple-mfd"?
> > 
> > I do. :)
> 
> Thanks Lee.
> 
> Thierry, any objections on the above mem-mapping?

If you have the mailbox as the child device and use "simple-mfd", you
don't need to slice up the memory do you?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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