Re: [PATCH v13 06/12] usb: xhci: use bus->sysdev for DMA configuration

From: Felipe Balbi
Date: Wed Feb 15 2017 - 06:52:36 EST


Roger Quadros <rogerq@xxxxxx> writes:
>>>>>>>> Why are we using sysdev to read DT property? We should be using the
>>>>>>>> XHCI device (&pdev->dev) here, no?
>>>>>>> If I remember correctly, this is one of the cases where pdev does not
>>>>>>> have a device node attached to it because it was created by the driver
>>>>>>> of the parent device on the fly in case of dwc3. When you have a pure xhci
>>>>>>> device in DT, the two pointers are the same.
>>>>>> From drivers/usb/dwc3/host.c
>>>>>>> if (dwc->usb3_lpm_capable) {
>>>>>>> props[0].name = "usb3-lpm-capable";
>>>>>>> ret = platform_device_add_properties(xhci, props);
>>>>>>> if (ret) {
>>>>>>> dev_err(dwc->dev, "failed to add properties to xHCI\n");
>>>>>>> goto err1;
>>>>>>> }
>>>>>>> }
>>>>>> So it is setting the usb3-lpm-capable property into the xhci platform device
>>>>>> and we should be reading the property from there.
>>>> Why dwc3 needs another "snps,usb3_lpm_capable"? Why not using
>>>> "usb3-lpm-capable" at firmware directly?
>>> dwc3 is not setting "snps,usb3_lpm_capable" but "usb3-lpm-capable" for the
>>> xhci platform device.
>>> What did you mean by firmware? Did you mean something like BIOS?
>>> At least TI platforms don't use any firmware like BIOS. So dwc3 driver
>>> needs to create a platform device for xhci on the fly and set the DT properties.
>> By readying code, the dwc3 calls dwc3_get_properties to set
>> dwc->usb3_lpm_capable, and at dwc3/host.c, it sets property
>> "usb3-lpm-capable" according to this flag, why not let common
>> code xhci-plat.c to get this property from sysdev which is DT
>> nodes for dwc3?
> Felipe, any comments?

Won't work. We have quirk flags which are based on DWC3's revision which
is not accessible by xhci-plat. Also, we can't call
device_add_property() because it's not really *adding*. It's *setting*,
meaning that we would loose all other properties.


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