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Date:   Tue, 6 Feb 2018 20:00:24 +0100
From:   Andreas Kemnade <andreas@kemnade.info>
To:     Bin Liu <b-liu@ti.com>
Cc:     <gregkh@linuxfoundation.org>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Tony Lindgren <tony@atomide.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@openphoenux.org>
Subject: Re: [PATCH] usb: musb: fix enumeration after resume
Message-ID: <20180206200024.18d40735@aktux>
In-Reply-To: <20180206184605.GA3992@uda0271908>
References: <20180127083403.928-1-andreas@kemnade.info>
        <20180206184605.GA3992@uda0271908>
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Hi,

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

> Hi,
>=20
> 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. =20
> =20
> Do you see the issue with the v4.15?
>=20
Yes. Tested without other patches.=20
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") =20
>=20
> 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.
>=20
Well reconfiguring gadget from userspace helps.

Regards,
Andreas

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