Re: [PATCH v2 2/3] usb: chipidea: imx: support disabling runtime-pm

[Francesco Dolcini]

Hello Luca,
I guess your mail to Philippe bounced, let me try to answer since I am aware
of the issue here.

On Thu, May 04, 2023 at 06:23:12PM +0200, Luca Ceresoli wrote:
> I found this thread after several hours spent in debugging why USB host is
> not detecting new devices on a custom board using the iMX6ULL Colibri
> SoM.
> 
> My best workaround at the moment is:
We have the same workaround in our BSP since quite some time, see
https://git.toradex.com/cgit/meta-toradex-bsp-common.git/tree/recipes-kernel/linux/linux-toradex-mainline-git/0002-drivers-chipidea-disable-runtime-pm-for-imx6ul.patch

> I haven't found any follow-up patches from you, so I'm wondering whether
> you have made any progress on this issue.
You can find the latest discussion on that regard here
https://lore.kernel.org/all/Y1vLpaxpc5WBCuGD@xxxxxxxxxxxxxxxxxxxxxxxxxxxx/

> As I see it, a quirk in the driver would make sense.
I am not sure.

The reason this is not working is that the VBUS is not directly
connected to the SOC and the USB IP is powered in a different way (all
of that was reviewed/acked by NXP when the board was designed).

The issue is in drivers/usb/phy/phy-mxs-usb.c:mxs_phy_disconnect_line(),
however:
 1 - checking for the VBUS when in host mode is not correct.
 2 - checking for the VBUS when in OTG/dual-role mode should be done using
 extcon or equivalent. In this case on the colibri-imx6ull you would get
 the correct behavior.

The NXP downstream kernel has some improvements on that regard, for
instance 1 would work, 2 I am not 100% sure.

Here the related patches: