On Mon, Oct 24, 2011 at 09:42:28AM +0300, Felipe Balbi wrote:
> Hi Grant,
>
> I have a question about how DeviceTree should be written in case a
> device has a child device.
>
> The way things are integrated on OMAP is that we will always have a
> parent device which is a wrapper around an IP core in order to
> integrate with the OMAP context (clocks, power management, etc).
>
> That wrapper has its own address space and its own IRQ number
> (generally). On my dwc3 driver I have modeled the OMAP wrapper as a
> parent device which allocates a child device for the core IP driver.
> This makes it a lot easier to re-use the core IP driver on other SoCs or
> PCI (there's a glue layer for PCI too).
>
> So I wonder if we should describe that on DeviceTree and not have the
> OMAP glue layer allocate the core IP driver. Just to illustrate, here's
> what we have:
>
> static int dwc3_omap_probe(struct platform_device *pdev)
> {
> struct platform_device *dwc3;
> struct resource res[2];
>
> dwc3 = platform_device_alloc("dwc3", -1);
> /* check*/
>
> dwc3->dev.parent = &pdev->dev;
>
> /* copy DMA fields from parent too */
>
> res[0].start = start_address;
> res[0].end = end_address;
> res[0].flags = IORESOURCE_MEM;
>
> res[1].start = irq_number;
> res[1].flags = IORESOURCE_IRQ;
>
> ret = platform_add_resources(dwc3, res, ARRAY_SIZE(res));
> /* check */
>
> return platform_add_device(dwc3);
> }
>
> and I wonder if I should have a DeviceTree like so:
>
> usb@xxxxx {
> compatible = "ti,dwc3-omap"; // This is TI OMAP
> // wrapper
> range = <....>;
>
> ...
>
> usb@yyyy {
> compatible = "synopsys,dwc3", // This is core IP
> // inside wrapper
>
> ...
> };
> };
>
> then I can drop the dwc3 platform_device allocation and all of that
> resource copying, etc.
>
> What do you think ?
Looks reasonable to me. of_platform_populate() should be able to
handle the device generation for you here.
g.
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