[BISECTED] arm64: dts: meson-sm1-odroid-hc4: USB not working

[Martin Blumenstingl]

Hi Pierre-Olivier, Hi Neil,

On Mon, Dec 26, 2022 at 11:48 PM Pierre-Olivier Mercier
<nemunaire at nemunai.re> wrote:
>
> Hi,
>
> On my Odroid-HC4, the USB 2.0 port (the only one available) was not
> working. While it seems I was not the only one in that case[1], after
> some experiments, I found that by reverting the following commit:
>
> 703e84d6615a4 arm64: dts: meson-sm1-odroid-hc4: disable unused USB PHY0
Thank you for bisecting the commit!

> it solves the issue: USB is working on latest stable (6.1.1) with this
> only patch reverted, while it doesn't with vanilla dtb (with same
> config otherwise).
[...]
> I didn't read the specs, but I also tried to inverse the patch (disable
> usb2_phy1 intead of usb2_phy0) and it didn't work neither. Apparently
> usb2_phy0 and usb2_phy1 are both required for some reason...
After reading this mail yesterday I could not make much sense of it.
Now, while re-reading it I remembered the time when I worked on GXL
USB support and wrote the following comment: [0]
  All USB2 PHYs (which are internally "connected" to the dwc3 roothub)
  need to be powered on, otherwise USB devices cannot be
  enumerated (even if just one PHY is disabled and if the device is
  plugged into another, enabled port)

This is probably also the reason why I left all USB PHYs enabled by
default in meson-{gxl,gxm}.dtsi (and so did we in
meson-g12-common.dtsi). Instead we're disabling the &usb node by
default (and enabling it for boards that have USB ports).
For readers not familiar with the default enabled/disabled: typically
we disable the nodes for IP blocks in the .dtsi and then each
board.dts enables them on demand.

Neil, what do you think about this?
Should Pierre-Olivier send a formal revert (with the problem being
described as part of the git commit message, such as in [1])?


PS: Neil has probably taken some days off, so please give him more
than usual time to reply.


Best regards,
Martin


[0] https://lore.kernel.org/all/20170814224542.18257-1-martin.blumenstingl@googlemail.com/T/
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=47722220660cfb935e27e62d385959ecc296cddb