Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev

Arnd Bergmann
2016-09-08T10:17:37Z

On Thursday, September 8, 2016 12:43:06 PM CEST Felipe Balbi wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
> > On Thursday, September 8, 2016 11:29:04 AM CEST Felipe Balbi wrote:
> >> > If we do that, we have to put child devices of the dwc3 devices into
> >> > the platform glue, and it also breaks those dwc3 devices that don't
> >> > have a parent driver.
> >>
> >> Well, this is easy to fix:
> >>
> >> if (dwc->dev->parent) {
> >> dwc->sysdev = dwc->dev->parent;
> >> } else {
> >> dev_info(dwc->dev, "Please provide a glue layer!\n");
> >> dwc->sysdev = dwc->dev;
> >> }
> >
> > I don't understand. Do you mean we should have an extra level of
> > stacking and splitting "static struct platform_driver dwc3_driver"
> > in two so instead of
> >
> > "qcom,dwc3" -> "snps,dwc3" (usb_bus.sysdev) -> "xhci" (usb_bus.dev)
> >
> > we do this?
> >
> > "qcom,dwc3" -> "snps,dwc3" (usb_bus.sysdev) -> "dwc3-glue" -> "xhci" (usb_bus.dev)
>
> no
>
> If we have a parent device, use that as sysdev, otherwise use self as
> sysdev.

But there is often a parent device in DT, as the xhci device is
attached to some internal bus that gets turned into a platform_device
as well, so checking whether there is a parent will get the wrong
device node.

> > That sounds a bit clumsy for the sake of consistency with PCI.
> > The advantage is that xhci can always use the grandparent device
> > as sysdev whenever it isn't probed through PCI or firmware
> > itself, but the purpose of the dwc3-glue is otherwise questionable.
> >
> > How about adding a 'compatible="snps,dwc3-pci"' property for the dwc3
> > device when that is created from the PCI driver and checking for that
> > with the device property interface instead? If it's "snps,dwc3"
> > we use the device itself while for "snps,dwc3-pci", we use the parent?
>
> Any reason why we wouldn't use e.g. dwc3-omap.dev as sysdev?

That would be incompatible with the USB binding, as the sysdev
is assumed to be a USB host controller with #address-cells=<1>
and #size-cells=<0> in order to hold the child devices, for
example:

/ {
omap_dwc3_1: omap_dwc3_1@48880000 {
compatible = "ti,dwc3";
#address-cells = <1>;
#size-cells = <1>;
ranges;
usb1: usb@48890000 {
compatible = "snps,dwc3";
reg = <0x48890000 0x17000>;
#address-cells = <1>;
#size-cells = <0>;
interrupts = <GIC_SPI 71 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 71 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>;
interrupt-names = "peripheral",
"host",
"otg";
phys = <&usb2_phy1>, <&usb3_phy1>;
phy-names = "usb2-phy", "usb3-phy";

hub@1 {
compatible = "usb5e3,608";
reg = <1>;
#address-cells = <1>;
#size-cells = <0>;

ethernet@1 {
compatible = "usb424,ec00";
mac-address = [00 11 22 33 44 55];
reg = <1>;
};
};
};
};

It's also the node that contains the "phys" properties and
presumably other properties like "otg-rev", "maximum-speed"
etc.

If we make the sysdev point to the parent, then we can no longer
look up those properties and child devices from the USB core code
by looking at "sysdev->of_node".

Arnd