[RFC usb-next v5 2/3] usb: core: add a wrapper for the USB PHYs on the root-hub

[Martin Blumenstingl]

Hi Alan,

thank you for taking the time to review my patches!

On Mon, Oct 9, 2017 at 7:16 PM, Alan Stern <stern at rowland.harvard.edu> wrote:
> On Sun, 8 Oct 2017, Martin Blumenstingl wrote:
>
>> Many SoC platforms have separate devices for the USB PHY which are
>> registered through the generic PHY framework. These PHYs have to be
>> enabled to make the USB controller actually work. They also have to be
>> disabled again on shutdown/suspend.
>
> ...
>
>> --- /dev/null
>> +++ b/drivers/usb/core/phy.h
>> @@ -0,0 +1,7 @@
>> +struct usb_phy_roothub;
>> +
>> +struct usb_phy_roothub *usb_phy_roothub_init(struct device *dev);
>> +int usb_phy_roothub_exit(struct usb_phy_roothub *phy_roothub);
>> +
>> +int usb_phy_roothub_power_on(struct usb_phy_roothub *phy_roothub);
>> +int usb_phy_roothub_power_off(struct usb_phy_roothub *phy_roothub);
>
> Have you considered the possibility that a phy might need three power
> states, for on, off, and suspended?
I have not considered this yet - on the Mediatek platform (tested by
Chunfeng Yun) _power_{on,off} works fine for a suspend/resume cycle.
the other platform this was tested on is Amlogic Meson GXL/GXM,
however we don't have suspend support there

the underlying code relies on the generic PHY framework, which has
*runtime PM* support, but no suspend/resume PM functions - see [0]

> Alan Stern
>


Regards,
Martin


[0] http://elixir.free-electrons.com/linux/v4.14-rc4/source/include/linux/phy/phy.h#L131