[PATCH] usb: ehci-mx6: Enable OTG detection on imx8mm and imx8mn

[Marek Vasut]

On 12/22/21 21:08, Adam Ford wrote:
> On Wed, Dec 22, 2021 at 1:31 PM Marek Vasut <marex at denx.de> wrote:
> 
>> On 12/22/21 13:52, Adam Ford wrote:
>>> The imx8mm and imx8mn appear compatible with imx7d-usb
>>> flags in the OTG driver.  If the dr_mode is defined as
>>> host or peripheral, the device appears to operate correctly,
>>> however the auto host/peripheral detection results in an error.
>>>
>>> Simply adding checks in ehci_usb_phy_mode for 8mm and
>>> 8mn in ehci_usb_phy_mode is not enough, because ehci_usb_of_to_plat
>>> is run before the clock is enabled which results in a hang.
>>>
>>> Enable the USB clock in ehci_usb_of_to_plat and add checks in
>>> ehci_usb_phy_mode for 8mm and 8mn to enable auto detection of
>>> the OTG mode on i.MX8M Mini and Nano.
>>
>> I was under the impression that of_to_plat() was meant to parse DT into
>> driver local data, so frobbing with clock there could be a problem,
>> right ? +CC Simon.
>>
> 
> If that's true, we'll likely need to move the functions from
> ehci_usb_of_to_plat to the probe function to run after the clocks are
> enabled, because the call to usb_get_dr_mode hangs without the clocks
> running.  usb_get_dr_mode tells the driver if it's a host or device mode.

Yes and this does not work, because you need to know whether the IP is 
in host and gadget mode before probe happens I think. Indeed, that's why 
OTG is unsupported thus far. But please do dig in and try to find a 
proper solution.

> We could make a temporary clock instead of passing the clock to the priv
> structure.  I intentionally shut the clock off as soon as we're finished
> reading the register so it didn't collide with the existing functions.

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