[PATCH V4] usb: ehci-mx6: Enable OTG detection on imx8mm and imx8mn

[Adam Ford]

On Sun, Feb 6, 2022 at 3:59 PM Marek Vasut <marex at denx.de> wrote:
>
> On 2/3/22 22:20, 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.
> >
> > The solution isn't just adding checks for imx8mm and imx8mn to
> > the check for imx7, because the USB clock needs to be running
> > to read from the USBNC_PHY_STATUS_OFFSET register or it will hang.
> >
> > Marek requested that I not enable the clocks in ehci_usb_of_to_plat,
> > so I modified that function to return an unknown state if the
> > device tree does not explicitly state whether it is a host
> > or a peripheral.
> >
> > When the driver probes, it looks to see if it's in the unknown
> > state, and only then will it read the register to auto-detect.
> >
> > Signed-off-by: Adam Ford <aford173 at gmail.com>
> > Tested-by: Tim Harvey <tharvey at gateworks.com>
> > ---
> > V4:  Fix 'err_clk' reference, so it is not encapsulated in
> >       an ifdef making it available at all times.
> > V3:  Keep ehci_usb_of_to_plat but add the ability to return
> >       and unknown state instead of reading the register.
> >       If the probe determines the states is unknown, it will
> >       query the register after the clocks have been enabled.
> >       Because of the slight behavior change, I removed any
> >       review or tested tags.
> >
> > V2:  Rename ehci_usb_of_to_plat to ehci_usb_dr_mode and call it
> >       from the probe after t
> >
> > diff --git a/drivers/usb/host/ehci-mx6.c b/drivers/usb/host/ehci-mx6.c
> > index 1bd6147c76..060b02accc 100644
> > --- a/drivers/usb/host/ehci-mx6.c
> > +++ b/drivers/usb/host/ehci-mx6.c
> > @@ -543,7 +543,7 @@ static int ehci_usb_phy_mode(struct udevice *dev)
> >                       plat->init_type = USB_INIT_DEVICE;
> >               else
> >                       plat->init_type = USB_INIT_HOST;
> > -     } else if (is_mx7()) {
> > +     } else if (is_mx7() || is_imx8mm() || is_imx8mn()) {
> >               phy_status = (void __iomem *)(addr +
> >                                             USBNC_PHY_STATUS_OFFSET);
> >               val = readl(phy_status);
>
> Is the USB GPCv2 power domain always ON at this point ? If it isn't,
> then this access will lock up the whole SoC.

The GPCv2 needs to be enabled if USB is going to be used, but I would
expect that to happen even without this patch.  I ran into that during
my early testing.

>
> You can check that easily by adding printf() into
> drivers/power/domain/imx8m-power-domain.c imx8m_power_domain_on() , and
> verify that printf() prints something before this ehci_usb_phy_mode()
> code is called.

I added a printf to show when a power domain is enabled.  It does
appear that power domains for HSIO, USBOTG1 and USBOTG2 are all
enabled before the scan on the respective USB bus happens, so I think
we're safe from hanging.

U-Boot 2022.01-00678-ge83818c782-dirty (Feb 06 2022 - 18:39:41 -0600)

CPU:   Freescale i.MX8MMQ rev1.0 at 1200 MHz
Reset cause: POR
Model: Beacon EmbeddedWorks i.MX8M Mini Development Kit
DRAM:  2 GiB
Core:  99 devices, 21 uclasses, devicetree: separate
WDT:   Started watchdog at 30280000 with servicing (60s timeout)
MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
Loading Environment from MMC... OK
In:    serial at 30890000
Out:   serial at 30890000
Err:   serial at 30890000
Net:   eth0: ethernet at 30be0000
Hit any key to stop autoboot:  0
u-boot=> usb start
starting USB...
Bus usb at 32e40000: imx8m_power_domain_on 0
imx8m_power_domain_on 2
USB EHCI 1.00
Bus usb at 32e50000: imx8m_power_domain_on 0
imx8m_power_domain_on 3
USB EHCI 1.00
scanning bus usb at 32e40000 for devices... imx8m_power_domain_on 0
imx8m_power_domain_on 2
1 USB Device(s) found
scanning bus usb at 32e50000 for devices... imx8m_power_domain_on 0
imx8m_power_domain_on 3
3 USB Device(s) found
       scanning usb for storage devices... 1 Storage Device(s) found
u-boot=>