imx8mp USB OTG/dual-role

[Ahmad Fatoum]

On 31.08.22 18:38, Tim Harvey wrote:
> On Tue, Aug 30, 2022 at 8:11 PM Jun Li <jun.li at nxp.com> wrote:
>>
>> Hi,
>>
>>> -----Original Message-----
>>> From: Jacky Bai <ping.bai at nxp.com>
>>> Sent: Wednesday, August 31, 2022 9:18 AM
>>> To: tharvey at gateworks.com; linux-usb at vger.kernel.org; Linux ARM Mailing
>>> List <linux-arm-kernel at lists.infradead.org>; Jun Li <jun.li at nxp.com>
>>> Cc: Alexander Stein <alexander.stein at ew.tq-group.com>; Jun Li
>>> <jun.li at nxp.com>; Rikard Falkeborn <rikard.falkeborn at gmail.com>; Lucas
>>> Stach <l.stach at pengutronix.de>; Philippe Schenker
>>> <philippe.schenker at toradex.com>; Felipe Balbi <balbi at kernel.org>; Fabio
>>> Estevam <festevam at denx.de>; Marcel Ziswiler <marcel.ziswiler at toradex.com>;
>>> Shawn Guo <shawnguo at kernel.org>; Marek Vasut <marex at denx.de>; Francesco
>>> Dolcini <francesco.dolcini at toradex.com>; Aisheng Dong
>>> <aisheng.dong at nxp.com>; Sascha Hauer <s.hauer at pengutronix.de>;
>>> dl-linux-imx <linux-imx at nxp.com>; Pengutronix Kernel Team
>>> <kernel at pengutronix.de>
>>> Subject: RE: imx8mp USB OTG/dual-role
>>>
>>> Jun, as we discussed before, any conclusion on how to handle the USB OTG
>>> ID pin in RM?
>>
>> The NXP datasheet for iMX8MP already changed the ID pin name to be with _DNU
>> suffix, RM may be updated in next version.
>> If legacy ID is going to be used, any normal GPIO function can be selected
>> for it, extcon is well supported in dwc3 controller driver.
>>
>> More comments for Tim, see below...
>>
>>>
>>>
>>> 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.
>>
>> So TPS25821 does not need a driver.
>>
>>>>
>>>> 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
>>
>> NXP iMX8MP EVK has not enabled type-C port due to the SS orientation
>> switch binding is still in discussion, but you don't need a SW control
>> in your case so you are okay here.
>>
>>>> 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?
>>
>> Could this dts work for you?
>>
>> /* Config the "ID" pin iomux to be GPIO */
>>
>> pinctrl_usb1: usb1grp {
>>                  fsl,pins = <
>>                       MX8MP_IOMUXC_GPIO1_IO13__USB1_OTG_OC    0x140
>>                       MX8MP_IOMUXC_GPIO1_IO10__GPIO1_IO10    0x140
>>           >;
>>  };
>>
>>  extcon_usb: extcon_iddig {
>>                  compatible = "linux,extcon-usb-gpio";
>>                  id-gpio = <&gpio1 10 GPIO_ACTIVE_HIGH>;
>>  };
>>
>>  &usb_dwc3_0 {
>>          pinctrl-names = "default";
>>          pinctrl-0 = <&pinctrl_usb1>;
>>                  extcon = <&extcon_usb>
>>          dr_mode = "otg";
>>  };
>>
>> Li Jun
> 
> Jun,
> 
> Thank you, this does appear to work as intended as dual-role. I was
> not aware of linux,extcon-usb-gpio.
> 
> And thanks also Alexander, your usb-dual-role via connector method
> works as well.
> 
> Which method is preferred, using extcon or using usb-role-switch via a
> connector as in Alexander's patch?

The commit adding the usb-role-switch
4602f3bff266 ("usb: common: add USB GPIO based connection detection driver")
mentions that "[d]ue to the requirement of usb-connector.txt binding, the old way
using extcon to support USB Dual-Role switch is now deprecated
when use Type-B connector."

> 
> Additionally, where is it appropriate to put the pinctrl for the OC
> and ID pins in the usb_dwc3_0 (dwc3 core) node, the usb3_0 (dwc3 glue)
> node, or the usb3_phy0 (phy) node?
> 
> Best Regards,
> 
> Tim
> 
> 


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