RE: imx8mp USB OTG/dual-role

[Jacky Bai <ping.bai@nxp.com>]

Jun, as we discussed before, any conclusion on how to handle the USB OTG ID pin in RM?


BR
Jacky Bai

> Subject: imx8mp USB OTG/dual-role
> 
> Greetings,
> 
> I have an imx8mp board (imx8mp-venice-gw74xx) which has a DWC3 USB
> host controller using imx8mp PHY
> (drivers/phy/freescale/phy-fsl-imx8mq-usb.c fsl,imx8mp-usb-phy) and
> DWC3 host controller core (drivers/usb/dwc3/core.c snps,dwc3) with imx8mp
> glue (drivers/usb/dwc3/dwc3-imx8mp.c fsl,imx8mp-dwc3).
> 
> One of the 2x USB 3.0 hosts is connected to a USB Type C connector using a
> TPS25821 USB power switch and config controller which handles the CC pins
> on and VBUS enable as well as drives the mux sel pin of a
> USB3 mux to route the USB SS pairs to the appropriate half of the Type C
> connector. This device has no I2C or other management bus - only VBUS,
> FAULT#, SINK#, and POL# outputs based on CC pins.
> 
> I'm not clear how to describe this in the device-tree in order for it to function
> as a dual-role controller for host vs device mode.
> 
> The TPS25821 has a FAULT# signal that routes to IMX8MP GPIO1_IO13
> pinmuxed as MX8MP_IOMUXC_GPIO1_IO13__USB1_OTG_OC and a SINK#
> signal that routes to IMX8MP GPIO1_IO10 pinmuxed as
> MX8MP_IOMUXC_GPIO1_IO10__USB1_OTG_ID. Additionally the VBUS
> output of the TPS25821 also connected to the TypeC VBUS pin routes to the
> IMX8MP USB1_VBUS pin.
> 
> I've noticed there are currently only 2 other IMX8MP boards in Linux mainline
> that specify dr_mode="otg"; the DH electronics i.MX8M Plus DHCOM SOM
> (imx8mp-dhcom-som.dtsi), and the Toradex i.MX8M Plus Verdin SOM
> (imx8mp-verdin.dtsi). I'm not clear how these are hooked up or if USB
> dual-role work on these currently. I did notice that imx8mp-verdin.dtsi looks
> like it does not enable the phy or core via status prop and uses invalid
> 'over-current-active-low' and 'disable-over-current' dt props.
> 
> I am currently using the following with imx8mp-venice-gw74xx:
> 
> /* USB1 - Type C front panel */
> &usb3_phy0 {
>         status = "okay";
> };
> 
> /* USB1 dwc3 glue */
> &usb3_0 {
>         fsl,over-current-active-low;
>         status = "okay";
> };
> 
> /* USB1 dwc3 core */
> &usb_dwc3_0 {
>         pinctrl-names = "default";
>         pinctrl-0 = <&pinctrl_usb1>;
>         dr_mode = "otg";
> };
> 
> &iomuxc {
>         pinctrl_usb1: usb1grp {
>                 fsl,pins = <
> 
> MX8MP_IOMUXC_GPIO1_IO13__USB1_OTG_OC    0x140
> 
> MX8MP_IOMUXC_GPIO1_IO10__USB1_OTG_ID    0x140
>                 >;
>         };
> };
> 
> And currently v6.0-rc2 enumerates the host controller even without a Type-C
> to host cable attached which tells me that OTG_ID isn't doing its job. I vaguely
> recall some confusing statements on the IMX community forum that these
> pins might not even be used on the IMX8MP.
> 
> How should I be describing the device-tree for this scenario in order to get
> dual-role behavior?
> 
> Best Regards,
> 
> Tim