Re: [PATCH 4/7] phy: meson: add USB2 PHY support for Meson8b and GXBB

Kishon Vijay Abraham I
2016-09-16T08:19:59Z

Hi,

On Friday 09 September 2016 09:44 PM, Martin Blumenstingl wrote:
> On Fri, Sep 9, 2016 at 5:33 PM, Kevin Hilman <khilman@baylibre.com> wrote:
>> However, the problem with all of the solutions proposed (runtime PM ones
>> included) is that we're forcing a board-specific design issue (2 devices
>> sharing a reset line) into a driver that should not have any
>> board-specific assumptions in it.
>>
>> For example, if this driver is used on another platform where different
>> PHYs have different reset lines, then one of them (the unlucky one who
>> is not probed first) will never get reset. So any form of per-device
>> ref-counting is not a portable solution.
> maybe we should also consider Ben's solution: he played with the USB
> PHY on his Meson8b board. His approach was to have only one USB PHY
> driver instance which exposes two PHYs.
> The downside of this: the driver would have to know the offset of the
> PHYs (0x0 for the first PHY, 0x20 for the second), but we could handle
> the reset using runtime PM without any hacks.

I think the offset information can come from the devicetree too. The phy can be
modeled something like below.

usb-phys@c0000000 {
compatible = "amlogic,meson-gxbb-usb2-phy";
reg = <0x0 0xc0000000 0x0 0x40>;
#address-cells = <2>;
#size-cells = <2>;
ranges = <0x0 0x0 0x0 0xc0000000 0x0 0x40>;
resets = <&reset 34>;

usb0_phy: usb_phy@0 {
#phy-cells = <0>;
reg = <0x0 0x0 0x0 0x20>;
clocks = <&clkc CLKID_USB &clkc CLKID_USB0>;
clock-names = "usb_general", "usb";
status = "disabled";
};

usb1_phy: usb_phy@20 {
#phy-cells = <0>;
reg = <0x0 0x20 0x0 0x20>;
clocks = <&clkc CLKID_USB &clkc CLKID_USB1>;
clock-names = "usb_general", "usb";
status = "disabled";
};
};

This way the driver will be probed only once (the reset can be done during
probe). The phy driver should scan the dt node and for every sub-node it
invokes phy_create?

Thanks
Kishon