Hello Jun Li,
On Tue, Nov 01, 2022 at 03:10:46AM +0000, Jun Li wrote:
> > On Mon, Oct 31, 2022 at 01:40:39PM +0000, Jun Li (OSS) wrote:
> > > > I am debugging some unexpected USB behavior on a i.MX6ULL SOC,
> > > > chipidea controller ("fsl,imx6ul-usb") and a fsl mxs usbphy
> > > > ("fsl,imx6ul-usbphy").
> > > >
> > > > The HW design has 2 USB interface, the first one is dual-role, while
> > > > the second one is a host port with NO way to re-read the VBUS
> > > > (USB_OTG2_VBUS is not really connected, there is just a capacitor to
> > > > GND).
> > >
> > > How is your USB_OTG1_VBUS status? Can you try to make your
> > > USB_OTG1_VBUS pad has a valid VBUS voltage, then run your Host only
> > > port test with runtime PM enabled?
> >
> > USB_OTG1_VBUS is tied to GND the same way as USB_OTG2_VBUS, not really
> > straightforward to do such a test.
>
> iMX6ULL need at least one valid VBUS(either from OTG1 or OTG2) as input to
> power the internal USB LDO if I understand correctly.
This surprise me a little bit, since
- the i.MX6ULL datasheet prescribe to keep the VBUS disconnected if
unused
- downstream NXP kernel seems to work fine ("seems" since we do have
some patches there, so I could be wrong)
- disabling runtime pm on upstream Linux kernel make it works
perfectly, so there is a way in SW to have this HW configuration
working.
> your HW to meet this: for Host only port, you have to connect USB_OTG2_VBUS
> to a valid VBUS and make it always present for simple.
> You can do some quick HW change to prove this.
We have no way to change the HW in reality, therefore doing a one off
test would be pretty much irrelevant.
Said all of that, given what you wrote, I feel like having a specific
dts property in the chipidea driver to disable runtime pm might be the
way to go.
Something like `ci,disable-runtime-pm`? I know the DTS is supposed to
describe the HW, so maybe a different property name would be required.
What do you think about this?
Francesco
