linux-kernel - Re: [PATCH] usb: musb: fix enumeration after resume

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Date:   Tue, 6 Feb 2018 12:46:05 -0600
From:   Bin Liu <b-liu@...com>
To:     Andreas Kemnade <andreas@...nade.info>
CC:     <gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Tony Lindgren <tony@...mide.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [PATCH] usb: musb: fix enumeration after resume

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?

> 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.

Regards,
-Bin.