usb: musb: fix enumeration after resume

[Andreas Kemnade <andreas@kemnade.info>]

Hi,

On Tue, 6 Feb 2018 12:46:05 -0600
Bin Liu <b-liu@ti.com> wrote:

> Hi,
> 
> On Sat, Jan 27, 2018 at 09:34:03AM +0100, Andreas Kemnade wrote:
> > On dm3730 there are enumeration problems after resume.
> > Investigation led to the cause that the MUSB_POWER_SOFTCONN
> > bit is not set. If it was set before suspend (because it
> > was enabled via musb_pullup()), it is set in
> > musb_restore_context() so the pullup is enabled. But then
> > musb_start() is called which overwrites MUSB_POWER and
> > therefore disables MUSB_POWER_SOFTCONN, so no pullup is
> > enabled and the device is not enumerated.  
>  
> Do you see the issue with the v4.15?
> 
Yes. Tested without other patches. 
It was also there in earlier kernels but I had not had motivation enough
to debug.

So maybe it deserves a CC: Stable


> > So let's do a subset of what musb_start() does
> > in the same way as musb_suspend() does it. Platform-specific
> > stuff it still called as there might be some phy-related stuff
> > which needs to be enabled.
> > Also interrupts are enabled, as it was the original idea
> > of calling musb_start() in musb_resume() according to
> > Commit 6fc6f4b87cb3 ("usb: musb: Disable interrupts on suspend,
> > enable them on resume")  
> 
> The logic in the fix makes sense, and I do see the same problem with
> AM335x on v4.9 kernel, but it doesn't happen on v4.15. I haven't checked
> if there is anything after musb_start() which sets MUSB_POWER_SOFTCON
> bit.
> 
Well reconfiguring gadget from userspace helps.

Regards,
Andreas